the effect of low velocity sediments on the mislocation vectors of the grf array summary the grf array is situated on jurassic limestone of the franconian alb in se germany the mislocation vectors show symmetry axes in their slowness and azimuth components for the slowness the line of separation is at about 95 against north the azimuth pattern shows a symmetry axis nearly perpendicular to the axis in the slowness pattern waves arriving from ne have a reduced slowness whereas waves from sw have a larger slowness the largest azimuth anomalies are found in the directions where the slowness components change direction these effects can to a large extent be modellfd by a low velocity sedimentary layer dipping to nne with about 0 8 dip such a sedimentary wedge correlates well with the geological data is able to reproduce the observed mislocation vector pattern and explains a major part of the observed traveltime residuals it furthermore demonstrates that local effects like the influence of sedimentary covers should be removed before inversion procedures and tomographic methods are applied

reinterpretation of late quaternary sediment chronology of lake biwa japan from correlation with marine glacial interglacial cycles a review of published stratigraphic records of pollen sediment grain size diatoms and organic matter composition from lake biwa japan identifies four pre holocene episodes of milder climate increased surface runoff and enhanced aquatic productivity indicating intervals of warmer and wetter conditions which are interpreted as being interglacial correlation of these episodes to times of marine interglacial periods revises the age scale of the lake biwa sediment sequence which has been based on fission track dating the revised chronostratigraphic scale proposes an age of ca 430 000 yr b p for the base of the 250 m thick t bed instead of the former age of ca 700 000 yr b p

mid cretaceous sequence stratigraphy and sedimentary cyclicity in the western paris basin abstract cenomanian and turonian depositional patterns of the western paris basin are interpreted in terms of sequence stratigraphy a system tract analysis of the epicontinental normandie basin with pelagic chalks and of the maine platform covered by clastics provides evidence for relative changes in coastal onlap various minor uncomformities are related to these changes of sea level the four global cycles uza or zc 2 2 2 5 of haq et al 1987 1988 are recognised while an additional one is proposed for the geslinianum zone in addition periodic rhythmic cycles are commonly registered within the chalk expressed by the repitition of various facies enhanced both by biosedimentary processes and diagenetic alteration these elementary climatic cycles allow accurate lithostratigraphic correlations during this period when the sea level peaked on the tectonically passive border of the armorican block the paris basin appears to record a detailed set of events which can be correlated with those in the atlantic boreal and tethyan provinces

eolian quartz flux to lake biwa central japan over the past 145 000 years abstract eolian quartz flux eqf g cm 2 103yr 1 to lake biwa central japan provides direct information on variations of the east asian winter monsoon lake biwa sediments spanning the past ca 145 000 yr are characterized by two main periods when eqf values were significantly greater than 5 50 g cm 2 103yr 1 and two main intervals during which eqf values were lower two periods with eqf values 5 50 g cm 2 103yr 1occurred from ca 145 000 to 125 000 and 73 000 to 13 000 yr b p while times of lower eqf values occurred from ca 125 000 to 73 000 yr b p and around ca 5500 yr b p between ca 125 000 and 73 000 yr b p three minimum eqf values and two intervening peaks of slightly higher eqf values are recorded eqf increased markedly from ca 73 000 to 13 000 yr b p whereas between ca 53 000 and 20 000 yr b p the values recorded were relatively lower than those recorded during either the preceding or the subsequent episodes the data imply that the east asian winter monsoon strengthened during the periods when eqf values were high and weakened during the intervals with low eqf values the eqf record of lake biwa can be correlated with the grain size record of the quartz fraction in chinese loess and with the specmap marine 18o record however the eqf record apparently lags ca 5000 yr behind the loess and 18o records during stage 6 5 and 2 1 transitions and ca 10 000 yr during stage 5 4 transition these apparent lags could be due to problems with the chronology alternatively they may imply that the eolian quartz flux depended more on the extent of dust source regions than on wind intensity during these transitions

facies architecture and sequence stratigraphy in glacially influenced basins basic problems and water level glacier input point controls with an example from the quaternary of ontario canada abstract sequence architecture is controlled by two fundamental factors the water level relative to the depositional surface which controls accommodation space and the points or areas of sediment injection which control how this space is filled in relative water level accommodation space and injection points normally vary together and various genetic terms are used to define systems tracts but in glacially influenced basins accommodation space is controlled not only by water level but also by the glacier injection points are similarly dually controlled by water level and by the terminus of the glacier during high lake levels the injection point of the glacier may be underwater at the base of the slope genetic terms like highstand and lowstand therefore are meaningless in successions controlled by sediment input points which are independent of water levels and accommodation space distinct water level and glacier input point systems can occur side by side the water level system controlled by lake level or sea level the glacier input point system controlled by the position of the subaqueous glacier front and both can form juxtaposed systems passing laterally into each other a bewildering and incompatible terminology is needed if the terms of genetic sequence stratigraphy are used for both water level and glacier input point systems because the sedimentary injection points and sequence boundaries of the two systems fluctuate out of phase with one another sequences developed by movement of the glacier are completely independent of those controlled by water levels if genetic sequence stratigraphy is applied to a basin with both lake level and glacier input point systems then each needs separate genetic terminologies to describe them which leads only to confusion however descriptive sequence stratigraphy allostratigraphy can be readily applied to successions like the quaternary of lake ontario we therefore suggest that genetic sequence terms be discarded and simpler allostratigraphic terminology used in glacially influenced basins

seismic anisotropy and velocity variations in the mantle beneath the saxothuringicum moldanubicum contact in central europe we report on results of a passive seismic experiment undertaken to study the 3 d velocity structure and anisotropy of the upper mantle around the contact zone of the saxothuringicum and moldanubicum in the western margin of the bohemian massif in central europe spatial variations of p wave velocities and lateral variations of the particle motion of split shear waves over the region monitor changes of structure and anisotropy within the deep lithosphere and the asthenosphere a joint interpretation of p residual spheres and shear wave splitting results in an anisotropic model of the lithosphere with high velocities plunging divergently from the contact of both tectonic units lateral variations of the mean residuals are related to a southward thickening of the lithosphere beneath the moldanubicum

late pleistocene continental climate and oceanic variability recorded in northwest pacific sediments core v21 146 provides a continuous record of northwest pacific pelagic sedimentation spanning the past 530 000 years downcore variations of 18o from benthic foraminiferal calcite were correlated to the specmap record to provide an age model for late pleistocene paleoclimatic and paleoceanographic variation fluxes of caco3 and eolian material have been determined by combining information about linear sedimentation rates bulk densities and component percentages the mass accumulation rate mar of caco3 varies from 58 to 1435 mg cm kyr 1 and exhibits the pacific ocean pattern of higher accumulation associated with glacial periods for the younger portion of the record however the pattern of caco3 accumulation appears to shift during the mid brunhes so that prior to 350 000 years ago it exhibits an opposite pattern of greater accumulation during interglacial periods the flux of eolian dust is a proxy measure of the source area aridity and correlates well to the loess soil stratigraphy in china dust fluxes range from 43 to 718 mg cm kyr 1 and are greater by a factor of about 4 during glacial times cross spectral analysis of the eolian flux and oxygen isotope records shows an inphase and coherent relationship at each of the major orbital periodicities of 100 41 and 19 kyr eolian grain sizes generally used as a proxy record of wind intensity range from 8 4 2 9 m to 6 2 13 6 m a change in grain size variability occurs near about 300 ka such that the older portion is characterized by lower frequency and higher amplitude fluctuations than the younger portion power spectra for the eolian grain size record show dominant peaks at 100 and 50 kyr and a broad 25 35 kyr peak but coherency to the oxygen isotope curve at only the 100 and 33 kyr periodicities the phase relationship for eccentricity between the eolian grain size and 18o records suggests that at the 100 kyr frequency the smallest grain sizes are associated with glacial conditions

chemical composition of a drilled core of lake biwa in japan and implications for source changes during the past 430 000 years abstract neutron activation analysis was performed on sediments taken from the 250 m thick sediment bed of lake biwa which is composed entirely of lacustrine clay and records paleo environmental change over the past 430 000 years a comparison is made between the geochemical compositions of cores from the center of lake biwa and lacustrine surface and terrestrial sediments from around lake biwa to estimate past changes in sediment sources time series of th sc ratios are synchronized with glacial interglacial climatic change and also correlated with the reported aeolian quartz flux data th sc ratios during the 18o stages 1 5 7 9 and 11 are approximately 1 1 1 2 whereas th sc ratios during the 18o stages 2 4 6 8 and 10 are approximately 1 0 1 1 the possibility of a contribution from the mafic area in the northwestern shore of lake biwa which has low th sc ratios ca 0 8 is excluded by the ti al ratio data as aeolian dust flux to the downwind area from the asian desert area is higher during glacial times this data suggests that aeolian dust reaching japan has an unexpectedly low th sc ratio of source material and or that there was a large shift in the amount of dust flux this assumption remains to be tested by future studies th sc ratios apparently lag ca 5000 years behind the marine 18o record during the stage 1 2 3 4 and 5 6 transitions which coincides with the aeolian quartz flux variation continuous increase of hf contents from ca 200 000 years bp could be mainly related to upheaval of the hf rich and high th sc ratio granite block on the west shore of drilling site by active fault movement the variations in delivery of high th sc granitic debris has damped the oscillation between th sc ratios of sediments and aeolian dust flux during oxygen isotopic stages 2 3 both the intermittent increase of na contents from ca 430 000 years bp to present and the abrupt increase of na content at ca 140 000 years bp are probably due to the subsidence of the northern basin as the result of tectonic movement around lake biwa

probing the core mantle boundary beneath europe and western eurasia a detailed study using pcp summary we use pcp the core reflected p phase recordings of deep earthquakes and nuclear explosions from the grafenberg germany and norsar norway arrays to investigate the core mantle boundary region beneath europe and western eurasia we find evidence for a previously unknown ultra low velocity zone 600 km south east of moscow located at the edge of a middle size low shear velocity region imaged in seismic tomography that is located beneath the volga river region the observed amplitude variations of pcp can be modelled by velocity reductions of p and s waves of 5 and 15 respectively with a density increase of 15 travel time delays of pre and postcursors are indicating a thickness of about 13 km for this ultra low velocity region ulvz however our modelling also reveals highly ambiguous amplitude variations of pcp and a reflection off the top of the anomaly for various ulvzs and topography models accordingly large velocity contrasts of up to 10 in vp and 20 in vs cannot be excluded in general the whole volga river region shows a complex pattern of pcp amplitudes caused most likely by cmb undulations further pcp probes beneath paris kiev and northern italy indicate likely normal cmb conditions whereas the samples below finland and the hungary slovakia border yield strongly amplified pcp signals suggesting strong cmb topography effects we evaluate the amplitude behaviour of pcp as a function of distance and several ulvz models using the 1d reflectivity and the 2d gauss beam method the influence of the velocity and density perturbations is analysed as well as the anomaly thickness the dominant period of the source wavelet and interface topographies strong variation of the pcp amplitude are obtained as a function of distance and of the impedance contrast we also consider two types of topographies undulations atop the cmb in the presence of flat ulvzs and vice versa where a broad range of cmb topography dimensions lead to large pcp amplitude variations only large ulvz undulations generate significant amplitude scattering consequently this indicates that topography effects of anomalies may mask the true medium parameters as well as the ulvz thickness moreover there might be a possibility of misinterpreting the precursor as pcp in particular for thin ulvzs

tectonic and climatic record of the lake biwa japan region provided by the sediments deposited since pliocene times abstract the sediments of lake biwa japan contain a potential record of eastern asian paleoclimates that date from the early pliocene a continuous drilled core of lake sediments with a recovery of 70 was obtained in 1982 1983 to allow study of this record dating of core samples by a combination of tephrochronology magnetostratigraphy and fission track methods has revealed that parts of the sedimentary record apparently are missing even though obvious discontinuities cannot readily be detected from lithostratigraphic and seismic data tectonically induced migration of the basin center from its former more southerly location may be responsible for several hiatuses in the sedimentary record which are more common in its earlier part the record during the brunhes epoch appears to be relatively complete sediments indicate warm cold changes in land vegetation which may record glacial cycles deeper sediments contain evidence of warmer climate late neogene flora tectonic events can be inferred from changes in sediment type and in sedimentation rates

response to high frequency sea level change in a fluvial to estuarine succession cenomanian palaeovalley fill bohemian cretaceous basin

retreat rates modalities and agents responsible for erosion along the coastal chalk cliffs of upper normandy the contribution of terrestrial laser scanning in order to follow all the changes affecting the coastal chalk cliff face in upper normandy and improve knowledge about cliff erosion repeated terrestrial laser scanning tls surveys were carried out frequently between 2010 and 2013 every 4 5 months they were conducted at two sites with similar lithostratigraphic characteristics but different exposures to marine actions the former being an abandoned cliff and the latter an active cliff they provide a quantification of the production of debris with centimeter precision from 0 01 to 0 04 m these surveys provided three major outcomes 1 cliff retreat rates were measured at high spatial resolution with retreat values unsurprisingly 3 4 times higher for an active cliff than for an abandoned cliff this result highlights that marine actions should be seen as not only a transport agent but also a particularly effective erosion agent 2 a significant proportion of debris fall production about 25 in the total active cliff retreat was identified and 3 one of the modalities of retreat was visualized as the creation of a basal notch which propagates instability towards the upper part of the cliff face later this instability generates rock falls coming from the whole cliff face

frequency dependent p wave polarization and its subwavelength near surface depth sensitivity near surface structure is crucial to assessing seismic hazards and understanding earthquakes and surface processes yet is a major challenge to robustly image recently an approach based on body wave polarization was introduced for constraining shallow seismic structure but the depth sensitivity of the polarization measurement has remained unclear using waveform simulations based on a layer over a half space we find that the depth sensitivity of p wave polarization peaks at the surface and decreases abruptly over a depth range shorter than its wavelength a strong frequency dependence provides constraints on local 1 d structure with frequencies between 0 1 and 10 hz illuminating structure at depths of 10 m to several kilometers applying these results to teleseismic recordings in japan provides constraints on structure at about 120 to 750 m including a distinctive weak zone along the median tectonic line in the kii peninsula and awaji island

seismic yield estimation using teleseismic p and pkp waves recorded at the grf grafenberg array summary in this paper the transportability of magnitude yield relations for nuclear explosions at the nevada test site nts usa is investigated this test of applicability is done by comparing the yield estimates obtained in this study for the nts and other test sites at eastern kazakhstan novaya zemlya and mururoa french polynesia to selected yield estimates of more large scale investigations using different and more comprehensive data sets it is shown that the transportability of magnitude yield relations becomes possible if the differences in the absorption of seismic body waves in the upper mantle beneath the different test sites are correctly accounted for to estimate the yields of explosions from the four test sites a single magnitude yield relation has been used and a uniform methodology has been applied for the determination of source region corrections for upper mantle attenuation a linear relation between the grafenberg station magnitude mb grf and the network magnitude of the isc is established which can be used to predict the network mb from a measurement of mb grf recordings from pkp waves from french nuclear explosions in mururoa can through the appropriate determination of a core phase magnitude mb grf be used analogously for yield estimation however because of the possible network bias problem for mb measurements of mururoa events and because of the less well known absorption correction the results for that test site must be considered less substantiated using the derived magnitude yield relations the smallest observed magnitudes can be converted into yield values the detection threshold of the grf array for the single station a1 lies in the kt range for the eastern kazakhstan and novaya zemlya test sites and in the 10 kt range for the nevada test site the detection threshold of the grf array beam for the mururoa test site lies in the kt range

array analysis of core phase caustic signals from underground nuclear explosions discrimination of closely spaced explosions abstract the grf grafenberg seismic array in germany is located at epicentral distances immediately before the pkp caustic b generated by underground nuclear explosions on the french atolls mururoa and fangataufa in the south pacific i use the large amplitude pkp waveforms to improve the locations of underground explosions near these french atolls the core phases are investigated using theoretical seismograms calculated with an extended reflectivity method near the caustic range the waveforms are strongly distance dependent due to a rapid decrease in pkp diff amplitudes before the caustic b on the basis of their different slownesses beam forming and velocity spectral vespagram analyses are used to identify pkp diff pkikp and pkikp which arrive within a few seconds of each other amplitudes and travel times of the weak secondary arrivals pkikp and pkikp are measured from the corresponding beams using a matched filter technique theoretical seismograms show a change in the amplitude ratio pkikp pkp diff by a factor of 2 for explosions separated by 30 km this distance dependent amplitude ratio is tested as a discriminant for closely spaced explosions using 31 mururoa and five fangataufa events on average the observed amplitude ratios agree with the theoretically expected amplitude ratio behavior with distance a combined analysis of travel time and amplitude data indicates that the investigated mururoa explosions were detonated beneath a relatively large area of the atoll ca 80 whereas on fangataufa explosion epicenters were concentrated within a small portion of the island this finding contrasts the isc pde epicenter determinations which due to insufficient station coverage locate the majority of the explosions outside of the rim of the atolls

seismic imaging of the site response using microearthquake recordings part i method abstract microearthquake signals from widely distributed geographical regions have been noticed repeatedly to be strongly affected by local site effects the corresponding seismograms contain important information on the individual propagation path a single station inversion method is presented which allows the imaging of the subsurface impedance structure from locally recorded sh waves records the technique is based on the kunetz claerbout equation which in its original form states the relationship between the transmission response and the reflection response for p waves in a horizontally layered medium and vertical incidence claerbout 1968 by adapting claerbout9s formulation to the transmission problem for sh waves under oblique incidence microearthquake recordings can be used to calculate corresponding pseudo reflection seismograms which in turn can be inverted for the impedance structure by exploiting levinson recursion limitations in the high frequency content of the signals due to the combined effects of absorption recording system and bandlimited source signals as well as the influence of noise drastically reduce the resolutional power of the inversion procedure a number of different deconvolution techniques have been tested with synthetic seismograms for the applicability to reduce these effects good results have been obtained with the blind deconvolution technique of scherbaum and stoll 1985 utilizing the minimum phase property of the green9s function from the analysis of synthetic data it can be expected that for realistic source receiver situations and short period recording systems the main reflectors down to a depth of several hundreds of meters could be resolved

large teleseismic p wavefront deflections observed with broadband arrays we measure the plane wavefront incidence azimuth for teleseismic p at large aperture 50 km broadband arrays the incidence azimuth is determined by crosscorrelation of the p arrivals on the vertical component seismograms filtered in successive frequency bands the periods considered range from 10 to 35 sec at the anza array in southern california the plane wave direction is deflected from the great circle azimuth of the event by up to 20 in addition we find a surprisingly strong frequency dependence of the same magnitude and a striking antisymmetric pattern of the deflection as a function of backazimuth whereas the curvature of the wavefront is small similar characteristics are found at the grafenberg array in germany and the norsar array in norway however with much weaker amplitudes of 5 we ascribe the behavior at anza to structure in the lower crust and uppermost mantle beneath the array given that the observations are only a function of source backazimuth and not of source depth and source mechanism that the wavelengths under consideration range from 50 to 270 km and that the sign of the deviation is opposite to that predicted from shallow crustal structure and moho topography we are able to reproduce the magnitude and frequency dependence of the wavefront deflection using finite difference numerical modeling of plane wave propagation through simple 2d structures

detecting compositional spatial and temporal attributes of glaucony a tool for provenance research abstract a reliable interpretation of glaucony bearing units requires the characterization of compositional spatial and temporal attributes of glaucony the criteria that can readily determine the differentiation of the various types of glaucony autochthonous parautochthonous or allochthonous intrasequential and detrital or allochthonous extrasequential are discussed in detail autochthonous vs allochthonous glaucony may be often detected on the basis of detailed sedimentological investigations including facies interpretation of glaucony bearing deposits and careful examination of spatial distribution of glaucony textural and morphological features although generally not diagnostic on their own provide a significant contribution to glaucony interpretation the distinction between parautochthonous and detrital glaucony can be sometimes performed by radiometric dating more commonly it requires that compositional attributes of glaucony be matched against those of putative sources glauconies from distinct parent rocks generally have different maturity and carry unique geochemical and mineralogical fingerprints that may contribute definitive data for provenance research previous work on glaucony and examples from units formed in tectonically stable areas cretaceous eocene deposits of paris basin and hampshire basin and active tectonic basin settings miocene strata of southern alps and northern apennines provide the opportunity to discuss the validity of the proposed criteria across different structural domains and emphasize the need for an integrated approach to the study of glaucony

the cenomanian turonian boundary event ctbe in northern lebanon as compared to regional data another set of evidences supporting a short lived tectonic pulse coincidental with the event abstract constrained by both foraminifera and isotope data the zeitoun and nahr ibrahim sections in northern lebanon record a steady flooding of the cenomanian carbonate platform during the uppermost cenomanian lower turonian interval the flooding began just before the inception of the ctbe 13c positive shift it is marked by the deposition of finely bedded to laminated fine grained limestone overlying platformal carbonates this scenario is entirely different to what has been published in northern israel where repeated emergences are instead recorded during the event a survey of published data from nearby middle east countries to north africa suggests that the ctbe is accompanied on a larger scale especially along the syrian arc by tectonic disturbances responsible for sequence stratigraphic heterogeneity and palaeogeographic changes detailed analysis of available data makes it possible to extract from the sedimentary record four sequence stratigraphic scenarios implying two phases of heterogeneity bounding the event and responsible for the outphasing of relative sea level changes in some sensitive areas these disturb a stepped early cenomanian to early turonian overall transgressive trend recorded in some large stable areas often used to support the concept of mesozoic eustasy the discussion focuses on the global processes that are possibly involved the hypothesized tectonic pulse does not explain the ctbe it is just another set of data to be taken into account in the search for causes

traveltime and amplitude anomalies at the seismic broad band may grf summary traveltime and amplitude residuals of p waves from teleseismic events show a positive correlation at the stations of the german seismic broad band array grf fast arrivals consistently have reduced amplitudes in the four frequency ranges considered short period bandpass wwssn sp filter broad band velocity and wwssn lp filter with the exception of the wwssn lp filter 40 60 per cent of the average of the relative traveltime and almost 100 per cent of the average of the amplitude residuals at individual stations with respect to the reference station a1 can be explained by near surface sediment layers these shallow structures are known from local and regional geology and are documented in borehole local refraction and polarization studies this aximuthal and distance independent term station average reaches values of up to 0 55 s and 0 15 units in log amplitude magnitude even after the removal of these station averages which also contain a trend of increasing crustal and uppermost mantle velocity from north to south large azimuthal and distance dependent relative traveltime and magnitude residuals can be observed across the array these residuals vary between 0 8 and 1 1 s and 0 54 and 0 72 magnitude units negative fast traveltime residuals are again related to negative magnitude residuals small amplitudes the azimuthal and distance dependent patterns of these residuals are identical within three distinct clusters of stations the main features of the residual patterns correlate well with the main fault systems and inhomogeneities near the array some of which have been postulated previously the velocity anomalies causing the azimuthal and distance dependent residuals are located in crust and uppermost mantle under the array and its vicinity the fact that local effects like sedimentary covers are responsible for 40 per cent or more of the station average residuals demonstrates again that site effects should be removed before tomographic methods are employed the simple stations corrections usually applied in global tomography might severely underestimate the influence of local and regional velocity anomalies since even after the removal of the station average residual large azimuthal and distance dependent traveltime and amplitude anomalies remain between stations less than 100 km apart these anomalies due to shallow inhomogeneities might then erroneously be mapped into features at greater depth

resolving shallow shear wave velocity structure beneath station cbn by waveform modeling of the mw 5 8 mineral virginia earthquake sequence abstract the 23 august 2011 m w 5 8 mineral virginia earthquake was the largest earthquake in the central and eastern united states in the past 100 years and it was well recorded by strong motion and broadband seismometers thus providing abundant ground motion data for earthquake ground motion studies the largest recorded ground motion among advanced national seismic system stations was at station cbn but the site effects at station cbn need to be understood because the strong motions recorded there do not represent bedrock site conditions on the radial component of these recordings the initial p wave is very weak and is followed by a strong signal 0 3 s later which is interpreted to be the s wave converted from the p wave ps at the interface between the sediments and bedrock we first estimate the subsurface shear wave velocity by modeling the ratio of the radial to vertical components of the initial p waves and then resolve the velocity structure and thickness of the unconsolidated sediments by modeling the ps wave the subsurface shear wave velocity is found to be approximately 300 m s consistent with field survey results the shear wave velocity at the bottom of the sediments is constrained to be in the range of 320 780 m s from which the thickness of the layer is estimated to be 100 230 m the estimates of shear wave velocity structure and thickness of the sediments are further improved by modeling the oscillatory waveforms between the p and s waves this study suggests that site characterization for the estimation of ground motion amplification at a site can be achieved inexpensively and noninvasively by modeling local p waveforms recorded at the site

foraminiferal evidence for cenomanian sequence stratigraphy and palaeoceanography of the boulonnais paris basin northern france abstract a middle to upper cenomanian chalk succession in the northwestern european paris basin escalles section was investigated with respect to its sediment composition biofacies and foraminiferal content most planktic foraminifers exhibit a high frequency cyclicity in their distribution pattern and show little relationship to the sequence stratigraphic subdivision a few characteristic species of benthic foraminifers tritaxia pyramidata ataxophragmium compactum dorothia levis and gavelinella cenomana are related in their frequency distribution to certain systems tracts other benthic foraminiferal species are more evenly distributed through the systems tracts cluster analysis and factor analysis allow the separation of three benthic foraminiferal biofacies domains which exhibit a characteristic frequency distribution pattern with respect to sequence stratigraphy biofacies 1 is dominant in the highstand systems tract hst and biofacies 3 is characteristic for the transgressive systems tract tst biofacies 2 is most abundant around the maximum flooding downlap surface mfs and less abundant around the sequence boundary factor analysis shows that most of the variance in the data set is explained by variables related to plankton productivity variables related to changes in water depth and changes in sea level have minor influence on the variance of the whole data set but have some influence on the variance of the benthic foraminiferal data set the different reaction of benthic and planktic foraminifers to relative sea level changes is also recorded in the total number of foraminifers per gram sediment foraminiferal number and in the ratio between planktic and benthic foraminifers p b ratio the foraminiferal number is highest at the mfs and lowest at the sequence boundaries of the investigated depositional sequences the p b ratio has no correlation with the sequence stratigraphic subdivision but shows a high frequency cyclicity the abundance pattern of planktic foraminifers is controlled by changes in the productivity of calcareous plankton the regular variation in calcareous plankton productivity leads to marl low productivity chalk high productivity cycles that form conspicuous couplets in the section the productivity cycles are also recorded in gamma ray logs in the environmental setting of the escalles section in contrast the abundance patterns of benthic foraminifers are more influenced by relative sea level changes changes in water depth and variations in substrate composition the stacking of probably precession controlled development of couplets lead to a distinct 100 000 year cyclicity that does not match very well with published sequence stratigraphic subdivisions

geochemistry of eolian dust in pacific pelagic sediments implications for paleoclimatic interpretations geochemical data rees th sc were determined for the operationally defined eolian dust oded fraction 63 m of late quaternary sediment samples n 57 from the north and equatorial pacific ocean paleoclimate studies commonly have assumed that this sediment fraction represents eolian materials from continental source regions this study shows on the basis of geochemical data published mineralogical data and mixing models that the oded fraction actually is a mixture of materials from two endmember sources the continental crust eolian transported weathering products and the oceanic crust primarily volcanogenic material mixing model results show that the average ash content is significant in the oded fraction equatorial pacific 43 north pacific 24 we have used this information to reconsider and refine the results of previous paleoclimate studies in the northwest pacific the flux of the eolian fraction is greater during glacial stages and shows a latitudinal maximum between 35 n and 42 n eolian fluxes are greatest during interglacial periods in the equatorial pacific these results are consistent with previous interpretations in contrast to previous assumptions eolian mass accumulation rates may not be a valid indicator of paleo aridity because they are correlated with grain size furthermore the relative abundance of the two endmembers is correlated with the average grain size of the dust fraction the continental crust component is associated with larger grains this compositional effect should be considered in future studies which commonly utilize grain size as a proxy indicator of paleo wind intensity

variations of the lithospheric seismic scattering strength below the massif central france and the frankonian jura se germany abstract small scale heterogeneities in the lithosphere below the frankonian jura se germany and the massif central france are studied using scattered teleseismic wavefields to compare both regions wavefields of earthquakes are analysed which were simultaneously recorded at permanent local networks because the average wavelets of the first p arrivals are nearly identical in the frankonian jura and the massif central it is possible to compare directly the scattering characteristics of the lithospheric environments although the overall form of the mean wavefields and the p codas are quite similar in both areas the intensity of the scattered seismic arrivals is increased in the massif central compared to the frankonian jura the same result is obtained using waveform data from mobile stations the increased seismic scattering strength in the massif central is interpreted as interaction of the incoming wavefield with solidified magmatic intrusions the lithospheric heterogeneities are most likely related to the known upwelling of the asthenosphere and the tertiary and quaternary volcanism in contrast the lithosphere beneath the frankonian jura seems to be less heterogeneous perhaps due to less structural alterations since its formation

geochemical history of ancient lake biwa in japan chemical indicators of sedimentary paleo environments in a drilled core abstract a comparison is made between the geochemical compositions of drilled sediment core samples from lake biwa and samples of surface sediments and from land around lake biwa to estimate paleo water depth spatial variability and past changes in sediment sources the al fe mn 10 diagram indicates that lake biwa has been an oligotrophic lake since its formation an investigation of the origin of a positive correlation between water depth and the mn al ratio in surface sediments is made and the historical change of paleo water depth in lake biwa proposed by koyama et al 1985 verfied demonstrated are the usefulness of both ti al ratio and ree pattern to detect changes in sediment sources and geochemical discontinuities in four layers which should indicate unconformities are found my data could be supporting evidence for the chronological assignment of takemura 1990 an explanation is given for the historical changes of source materials in drilled core samples associated with tectonic changes on the basis of the historical basin development postulated by yokoyama 1984

sea level changes and geochemical anomalies across the cenomanian turonian boundary pecinov quarry bohemia relationships between geochemical anomalies sea level change and other events were studied in the cenomanian turonian boundary interval in the pecinov quarry in southwestern part of the bohemian cretaceous basin czech republic a major 3rd order sea level rise at the base of the late cenomanian m geslinianum zone was followed by deposition of organic enriched mudstones in a succession of parasequences deposited in response to high frequency 4th order sea level fluctuations and recording a stepwise decrease in bottom oxygenation towards intensely dysaerobic conditions a complex 13c excursion occurs in total organic matter of the late cenomanian deposits a sequence boundary of latest cenomanian age in the pecinov section is correlated to a global sea level fall during the n juddii zone a renewed sea level rise occurred during the early turonian w coloradoense zone and reached maximum flooding during the m nodosoides zone during the early turonian bottom waters were generally aerobic and the positive 13c excursion waned early in the w coloradoense zone the magnitude of the 13c excursion more than 4 is approximately the same as in north america and northern africa confirming that it was controlled by a global paleoceanographic mechanism the absence of anoxia and a 13c anomaly during the peak flooding of early turonian age suggests that widespread deposition of organic enriched deposits as well as the positive shift in 13c generally did not depend on the absolute elevation of sea level but rather on the area of newly flooded land during transgression abrupt small scale shifts in 13c towards higher values coincide with the flooding surfaces of parasequences and may reflect either regional changes in the proportion of marine and terrestrial organic matter or rapid global changes in isotopic composition of marine organic matter related to high frequency sea level changes abundances of ir sc cr v and other elements previously reported as forming anomalous concentrations in the boundary interval showed no enrichment in the bohemian section this is most probably due to the large distance of the depositional site from the presumed volcanic source of element enriched deep waters in the proto caribbean region anomalous concentration of mn at the base of the turonian deposits was caused by diagenetic incorporation of mn into siderite

yields of soviet underground nuclear explosions from seismic surface waves compliance with the threshold test ban treaty abstract magnitudes of the larger soviet underground nuclear weapons tests from the start of the threshold test ban treaty in 1976 through 1982 are determined for short and long period seismic waves yields are calculated from the surface wave magnitude for those explosions at the eastern kazakh test site that triggered a small to negligible component of tectonic stress and are used to calibrate body wave magnitude yield relationship that can be used to determine the sizes of other explosions at that test site the results confirm that a large bias related to differential attenuation of p waves exists between nevada and central asia the yields of the seven largest soviet explosions are nearly identical and are close to 150 kilotons the limit set by the threshold treaty

geochemical characterization of the luochuan loess paleosol sequence china and paleoclimatic implications abstract chemical major and trace element and isotopic sr nd analyses of the luochuan loess paleosol sequence in china were performed in order to examine the following problems 1 potential source heterogeneity 2 element behavior during pedogenesis 3 paleoclimatic implications and 4 the use of loess data to determine the average composition of the upper continental crust new results clearly indicate that rb sr u and ce abundances are severely depleted in paleosols relative to their parental loess the behavior of these elements is strongly controlled by the breakdown of primary minerals such as carbonate sr or by alteration processes in highly oxidizing environments ce and u the pattern of element variations through the upper section of the luochuan sequence mimics the magnetic susceptibility signal both in position and in intensity thus reinforcing the pedogenesic origin of the enhanced magnetic susceptibility in paleosols all loess samples display highly uniform ree patterns except for ce characterized by the upper continental crust ucc ratios la yb n 10 and eu eu 0 66 the paleosol ree patterns are similar to those of the loess with the same lree hree fractionation but they also show distinct and variable negative ce anomalies nd and sr isotopic compositions are rather uniform in both loess and paleosols and do not vary with stratigraphic position nd 10 5 to 9 2 87 sr 86 sr 0 715 to 0 719 the isotopic homogeneity in the luochuan sequence strongly suggests a uniform source region during the entire period of deposition since 800 ka ago to the present several conclusions may be drawn from the present study 1 1 no geochemical distinction can be made between loess layers l1 to l7 the sources and the dust storm trajectories must have been essendally the same for the last 800 ka 2 2 some elements e g ca rb sr u ce are strongly fractionated by pedogenesis between loess and paleosols ce mobility in soils is clearly demonstrated but the process responsible for this leaching is still poorly understood 3 3 systematic variations of element abundances and ratios between loess and paleosols can be used as chemical indicators for pedogenesic intensity and so for paleoclimatic change these chemical indicators serve a function similar to that of oxygen isotopes in deep sea sediments pelagic foraminifera or that of magnetic susceptibility in loess sequences they are different recorders of paleoclimatic change 4 4 the striking uniformity of ree patterns and la th ratios in the luochuan loess and paleosols as well as in loess worldwide is an excellent starting point for estimating the average composition of the upper continental crust

chondrites a trace fossil indicator of anoxia in sediments the trace fossil chondrites a highly branched burrow system of unknown endobenthic deposit feeders occurs in all types of sediment including those deposited under anaerobic conditions in some cases such as the jurassic posidonienschiefer formation of germany chondrites occurs in black laminated carbonaceous sediment that was deposited in chemically reducing conditions in other cases such as numerous oxic clastic and carbonate units throughout the geologic column chondrites typically represents the last trace fossil in a biotutbation sequence this indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters

isotope geochemistry of quaternary deposits from the arid lands in northern china abstract quaternary deposits of various types lacustrine desert sand river loess and loess like deposits from the southwestern tarim basin north tianshan northeast china and the central loess plateau exhibit an nd 0 range from 5 to 12 8 and a 147 sm 144 nd range from 0 110 to 0 140 their nd depleted mantle model ages are between 1 50 and 1 92 ga with a mean value of 1 7 ga th sc ratios vary over a wide range from 0 1 to 2 comparison of these geochemical signatures with those of the old australian shales and modern pacific ocean dust suggests a continuous input of mantle derived material into the crust over geological time the deposits from the north tianshan show clearly different chemical and isotopic features with significantly higher sm nd high 143 nd 144 nd low 87 sr 86 sr and low la lu and th sc ratios relative to those in the deposits from the other areas this indicates a geological control on the local source which has an overall young age and an enrichment of basic components the ce 0 values of two loess samples from the central loess plateau are 1 8 and 3 9 corresponding to depleted mantle model ages of 2 2 and 3 4 ga like the rb sr system the evolution of the la ce isotopic system in the crust may be to some extent decoupled from the sm nd system due to la ce fractionation by sedimentary processes the loess deposits and the desert sand are not distinguishable in isotopic composition but show somewhat different chemical compositions we conclude that the loess can have originated from desert processes since the difference in the chemistry of the desert sand and loess may result from mineral sorting during desert processes and aeolian transportation the loess deposits on the central loess plateau chemically and isotopically resemble the desert loess deposits in the southwestern tarim basin but do not resemble those of the north tianshan accordingly the loess on the plateau may have a source region in the tarim basin but clearly not in the north tianshan

chronology and processes of fluvial terrace formation in northeastern kinki district southwest japan based on cryptotephra analysis abstract kinki district is a tectonically active area in southwest japan this area is located far from active volcanoes and eolian deposits covering fluvial terrace deposits are not as thick as those in kanto district thus terrace chronology and processes of terrace formation previously were poorly established in kinki district cryptotephra analysis identified invisible tephra horizons in eolian deposits covering fluvial terrace deposits in takashima sekigahara and inabe regions including the kikai akahoya tephra k ah 7 3 ka aira tn tephra at 26 29 ka and kikai tozurahara tephra k tz 95 ka horizons taisanjino 1 terrace in takashima and md1 terrace in inabe were formed during marine isotope stage mis 5e and nakano terrace in takashima l2 terrace in sekigahara and l2 terrace in inabe were formed during mis 2 based on their ages and geomorphic features aggradational terraces formed during mis 2 exhibit similar geomorphic features among the three regions although these regions have different base levels of erosion and active fault movements this means that the terrace formation during mis 2 was mainly affected by climate changes not by base level changes and active fault movements the main factor of terrace formation during glacial periods was the decrease in precipitation and water discharge due to climate changes because the study area was not affected by glacial and periglacial processes during mis 2 this indicates that aggradational terraces formed during glacial periods not only in glacial and periglacial areas but also in non glacial and non periglacial areas from processes of terrace formation during mis 5e the tectonic base level descent was important for terrace formation during interglacial periods because terraces were formed during mis 5e by active fault movements in the takashima region despite small lake level changes uplift rates of the kamidera and kuwana faults were 1 08 mm y and 0 5 mm y respectively based on the height of terrace surfaces formed during mis 5e

origin of channel systems in the upper cretaceous chalk group of the paris basin abstract the upper cretaceous chalk group of the anglo paris basin is known to show wedging beds and channel like features which disrupt the quietly deposited pelagic chalk that covered most of nw europe in the late cretaceous two d reflection seismic data from the brie region se of paris show the presence of at least two distinct intra chalk discordant reflections a top santonian and a mid campanian reflection these reflections are in places associated with up to 120 m deep channel like structures trending preferentially n s and nw se the mid campanian reflection is also sporadically associated with a massive secondary dolomite layer the thicknesses of which may reach 110 m diagenesis does not seem to account for the formation of the discordant reflections as there is neither a one to one relationship between the dolomite and discordant reflections nor are there signs of systematic collapse of the cenozoic succession over the channel like features as a result of intra chalk dissolution both reflections correlate with indurated chalk layers and hardgrounds and represent real unconformities the mid campanian reflection is furthermore associated with a stratigraphic hiatus a submarine origin is suggested due to the uninterrupted deep marine chalk facies below and above both unconformities and the unrealistically large sea level drop of more than 200 m which would be necessary for subaerial exposure of the central paris basin during the campanian the channels are oriented parallel to the margins of the basin and important bathymetric elements which could induce erosion by slope failure are not observed the channels are thus interpreted as having formed by strong mainly slope parallel bottom currents major channeling events are common in the chalk group throughout nw europe and represent palaeoceanographic re organization of bottom currents probably driven by changes in sea level and water temperature

the crustal structure from teleseismic p wave coda ii application to data of the nars array in western europe and comparison with deep seismic sounding data summary the crustal structure beneath a seismic station has a large influence on the p wave coda recorded by that station in this study we employ the vertical and radial component of the crustal receiver response to determine the most important features of the crustal velocity structure beneath stations of the nars array the receiver response is estimated from the p wave coda of teleseismic events by deconvolution with a source wavelet and by stacking responses of different events the crustal velocity structure at the station is derived from these data by non linear waveform inversion the responses of some of the nars stations show anomalous features such as an apparent delay of the first arrival on the radial component relative to the onset on the vertical component this appears to be a combined effect of very low velocities in the top layer of the model and a strong velocity discontinuity in the uppermost part of the crust a high amplitude coda on the radial component is observed for stations on a structure with strong s velocity gradients in the upper crust the receiver responses of the nars stations are generally well modelled by the synthetics of the final models of the inversions the method provides an adequate procedure to estimate the dominant effects of the crustal structure at the site with the models representing the most significant velocity gradients of the crustal structure

the calcareous nannofossil biostratigraphic framework of the late maastrichtian danian north sea chalk abstract the calcareous nannofossil biostratigraphy of cored maastrichtian tor formation and danian ekofisk fm chalk sections from 10 selected wells of the greater ekofisk area central north sea was studied wells come from the edda tor se tor ekofisk and eldfisk fields among others more than 1000 m of cores were examined and about 500 samples were selected and analysed most of them quantitatively the main emphasis was placed on the danian sequence and on the k t boundary biostratigraphy provided detailed subdivision for the danian sediments intra danian hiatuses were detected and consistently recorded at the regional scale extensive mass movement was observed highlighting the complex depositional history during this time interval intervals of cretaceous chalk were found embedded in the danian sequence well 2 5 7 redeposited by slides as discrete chalk packages similarly lower danian intervals were recognised as transported into younger danian sediments well 2 4 b19a an attempt to reconstruct a regional stratigraphic picture for the area north of edda field including ekofisk se tor and tor fields has been made this suggests the following salient features the k t boundary of three wells of the northern sector of the studied area tor field is preceded by a prediscosphaera stoveri acme suggesting the presence of a rather complete maastrichtian sequence below the boundary above the k t boundary a few tens of centimetres of generally clay enriched pelagic chalk of the basal danian d1 biantholithus sparsus zone are present in most of the studied wells above this a condensed section often marked by hard ground levels or clay rich intervals was detected in almost all the wells the sedimentary expression of upper d1 above cruciplacolithus primus fad d2 and d3 time interval is lacking or extremely reduced in some cases sediments whose age is near the early late paleocene boundary were found unconformably overlying pelagic chalk referred to d5 d6 biozones

composite ichnofabrics and tiering of burrows infaunal communities in marine environments typically are tiered that is different taxa live at different depths within the sediment tiered suites of biogenic structures yield complex biogenic sedimentary fabrics ichnofabrics with the traces of deep burrowing organisms overprinted on those of shallow burrowing organisms careful analysis of crosscutting relationships of burrows in such composite ichnofabrics allows reconstruction of the tiered nature of fossil endobenthic communities it is important to recognize that the best preserved and most prominently displayed trace fossils in most assemblages usually represent the deepest tier thus they were farther removed from the sea floor and therefore less indicative of actual sea floor conditions than the more poorly preserved traces of the shallower tiers on which the deeper traces are juxtaposed

validation of arsenic as a proxy for lake level change during the past 40 000 years in lake biwa japan abstract lake biwa is the largest lake in japan it is a semi closed lake surrounded by active faults and was oxygen rich prior to the industrial revolution in this lake arsenic concentration in core sediments was proposed as a proxy for lake level change due to a strong correlation between as concentration in recent sediments and water depth detailed elemental variations from two piston cores from water depths of 76 and 67 m were obtained from the center of the lake to examine the possible correspondence between as concentrations and paleo environmental change during the past 40 000 years the vertical fe distribution pattern indicates that precipitated fe hydroxide the adsorbent of as ions from lake water has been preserved in buried sediment due to oxic conditions the change in the ti al ratio suggests that the rapid drop of as content through the last several centuries is due to the increasing inflow of clayey materials generated by human activity diluting the hydrogenous component the as contents are fairly constant between 2000 and 9000 yr bp and the fluctuation of equivalent water depth was 10 m at most the increase of as content and equivalent water depth during the last two millennia should be coincident with the lake level rise event at about 2000 yr bp as suggested by previous investigations however during the last 40 kyr the extent of change of equivalent water depth is too large to explain only by tectonic movement from about 40 cal kyr bp to 30 cal kyr bp as contents significantly increased and then gradually decreased until mid holocene the change at 30 cal kyr bp should correspond with climatic change from wet to dry at the marine oxygen stage 2 3 transition with some time lag increases of as content are synchronized with events marked by abrupt increases in precipitation arsenic was dissolved in lake water as a consequence of rock and soil weathering around lake biwa and then immediately precipitated with iron hydroxide into the lake sediment our results revealed that the historical change of as contents in core samples was influenced by the amount of as inflow to the lake from the watershed area as well as by lake level change chemical analysis of the extracts of the hydrogenous component of the samples confirmed this hypothesis

shallow structure effects on broadband teleseismic p waveforms the first 5 sec of source equalized p wave receiver functions from an array of broadband portable instruments located about 50 km from the coast in western washington are strongly influenced by very shallow structure depths less than 3 km these data display behavior associated with a dipping high velocity contrast interface at shallow depths the direct p wave and the p to s converted phase vary strongly with backazimuth producing an apparent delay in first arriving energy at western backazimuths these patterns are attributed to a shallow contact between low velocity sandstones at the surface and an underlying high velocity volcanic unit this shallow structure influences even the original unprocessed teleseismic p waves suggesting that such shallow structure could affect other studies such as seismic source analysis utilizing broadband data

the development and seismic expression of synsedimentary features within the chalk of southern england seismic reflection data acquired onshore to the north of bournemouth southern england image clearly a series of prominent concave up troughs or depressions and concave down mounded structures within the white chalk subgroup the chalk lithostratigraphy in the area of study is established from borehole geophysical log correlations these correlations then provide calibration of the seismic reflection data indicating that the structures are concentrated at levels between the lewes nodular chalk formation and tarrant chalk member and towards the base of the portsdown chalk formation onlap downlap and truncation of reflectors are observed with the most dramatic features forming a stacked series directly overlying faulting of jurassic strata similar stratal geometries have been described from comparable levels in the chalk of the north sea and in outcrop in britain and france to many they represent channels formed by submarine erosion and redeposition of the chalk during relative sea level falls linked to tectonics we also interpret a number of apparently incisive structures and slumped infill sequences described here as being of primary syndepositional origin the slumping and the close association of these features with underlying faults and proximity to nearby major crustal faults may be indicative of submarine erosion of the chalk caused by sea level changes linked to syndepositional fault movements however evidence of toplap downlap pairs is also suggestive of more aggradational mounding or laterally migrating surfaces or facies belts the presence of any such structures implies rapid lateral variations in the chalk that would have implications not only for aquifer management and future storage schemes but also during the processing of seismic reflection data and general studies and correlations of the chalk across southern britain

sediment structure at grf from polarization analysis of p waves of nuclear explosions near vertical incidence angles and quasi elliptical particle motions characterize broadband p waves from nuclear explosions recorded at the three 3 component stations of the grafenberg array grf in southern germany which is situated on the jurassic sediments of the franconian jura comparison with data from the broadband stations khc ka perske hory czech republic and ksp ksiaz poland located on gneiss in the bohemian massif and precambrian sediments respectively show that the observed effect is caused by local receiver conditions polarization analysis shows that p to sv wave conversions at the basement sediment boundary and multiples in the sedimentary layers are mainly responsible for these observations at the grf array borehole and refraction data confirm low p wave velocities in the sediments under the grf stations by modeling the broadband particle motions of the p waves of nuclear explosions average models for the sedimentary layers below the grf stations are derived the main modifications to the model of aichele 1976 are one grf c1 and two low velocity layers grf b1 and grf a1 between the out cropping limestone and the basement the first low velocity layer has an s wave velocity of about 1 0 km sec and a thickness of about 200 m below the three 3 component stations and a p wave velocity about 2 8 km sec which is not well constrained the second low velocity layer underlying the first low velocity layer at the stations grf b1 and grf a1 has a lower p wave velocity of about 2 4 km sec but a higher s wave velocity of about 1 6 km sec together with the surficial limestone layer about 200 m thick the total thickness of the sediment column increases from about 400 m below grf c1 in the south to about 750 m below grf b1 and to about 1150 m below grf a1 in the north slow sediment layers near the surface are important for the polarization of teleseismic p waves in turn polarization analysis of broadband recordings can be used to analyze the structure of shallow sediment layers

geochemical identification of cryptotephras using inaa from late quaternary hemipelagic sediments southwest japan abstract we present new compositional data on glass shards from cryptotephra layers in five marine sediment cores from the southern japan east sea the hand picked glass shards were extracted from cryptotephra horizons that were distinguished by sem eds for major elements and inaa for trace elements on individual shards most of the glass shards have alkaline and trachyte phonolite compositions and have major and trace element compositions similar to eruptive units on ulleung island stratigraphic inferences indicate the presence of at least four alkaline tephras u 3 post u oki u oki and pre u oki in the interval between the k ah rhyolitic tephra 7 3 cal ka bp and the tl1 regional dark sediment layer 11 8 cal ka bp the new trace elements on glass shards indicate minor compositional distinctions from one visible tephra and four cryptotephras that help to infer fine scale regional correlations the development of a more comprehensive alkaline tephrostratigraphical framework for this region will greatly aid in the reconstruction and chronology of regional stratigraphic variations the recognition of new alkaline cryptotephras in the marine sediments of the japan east sea also contributes towards a better understanding of the volcanic history of ulleung island and nearby seamounts

oceanic lithospheric s wave velocities from the analysis of p wave polarization at the ocean floor our knowledge of the absolute s wave velocities of the oceanic lithosphere is mainly based on global surface wave tomography local active seismic or compliance measurements using oceanic infragravity waves the results of tomography give a rather smooth picture of the actual s wave velocity structure and local measurements have limitations regarding the range of elastic parameters or the geometry of the measurement here we use the p wave polarization apparent p wave incidence angle of teleseismic events to investigate the s wave velocity structure of the oceanic crust and the upper tens of kilometres of the mantle beneath single stations in this study we present an up to our knowledge new relation of the apparent p wave incidence angle at the ocean bottom dependent on the half space s wave velocity we analyse the angle in different period ranges at ocean bottom stations obs to derive apparent s wave velocity profiles these profiles are dependent on the s wave velocity as well as on the thickness of the layers in the subsurface consequently their interpretation results in a set of equally valid models we analyse the apparent p wave incidence angles of an obs data set which was collected in the eastern mid atlantic we are able to determine reasonable s wave velocity depth models by a three step quantitative modelling after a manual data quality control although layer resonance sometimes influences the estimated apparent s wave velocities the apparent s wave velocity profiles are well explained by an oceanic prem model in which the upper part is replaced by four layers consisting of a water column a sediment a crust and a layer representing the uppermost mantle the obtained sediment has a thickness between 0 3 km and 0 9 km with s wave velocities between 0 7 km s 1 and 1 4 km s 1 the estimated total crustal thickness varies between 4 km and 10 km with s wave velocities between 3 5 km s 1 and 4 3 km s 1 we find a slight increase of the total crustal thickness from 5 km to 8 km towards the south in the direction of a major plate boundary the gloria fault the observed crustal thickening can be related with the known dominant compression in the vicinity of the fault furthermore the resulting mantle s wave velocities decrease from values around 5 5 km s 1 to 4 5 km s 1 towards the fault this decrease is probably caused by serpentinization and indicates that the oceanic transform fault affects a broad region in the uppermost mantle conclusively the presented method is useful for the estimation of the local s wave velocity structure beneath ocean bottom seismic stations it is easy to implement and consists of two main steps 1 measurement of apparent p wave incidence angles in different period ranges for real and synthetic data and 2 comparison of the determined apparent s wave velocities for real and synthetic data to estimate s wave velocity depth models

trace fossil model for reconstruction of paleo oxygenation in bottom waters recognition of fluctuations in the degree of paleo oxygenation of bottom waters recorded in fine grained pelagic strata is important for interpretation of paleoceanographic and paleoclimatologic conditions general sedimentary fabric composition of trace fossil assemblages and burrow size and crosscutting relationships have been incorporated into a trace fossil tiering model that permits detailed reconstruction of changes in paleo oxygenation of bottom waters applications of this model to the miocene monterey formation california and the cretaceous niobrara formation colorado indicate that the ichnologic approach is more sensitive to both magnitude and rates of change in oxygenation levels compared to macrobenthic body fossil information

integrated depositional model for the cenomanian turonian organic rich strata in north africa abstract during the late cenomanian early turonian c t oceanic anoxic event oae2 organic rich strata was deposited in rift shelf basins and slopes across north africa and in deep sea basins of the adjacent oceans based on a review of published and unpublished information this paper documents the distribution and organic richness of c t strata across the whole region within a palaeogeographic framework and systematically analyses the conditions and processes which controlled their deposition previously the c t in north africa has been most intensively studied in southern morocco tarfaya and tunisia only little data is availabe for other parts of north africa namely algeria libya and egypt because distribution of c t corg strata there becomes more patchy a general decrease in peak organic richness and black shale thickness occurs from west to east partly as a result of upwelling along the moroccan atlantic coast and the absence of upwelling in the eastern mediterranean area furthermore in the confined central atlantic the oxygen minimum zone omz in many places reached down to the deep sea floor 3 4 km while the lower limit of the omz along the north african tethys was much shallower and underlain by oxic water masses as documented by high resolution biostratigraphic and chemostratigraphic data c t black shale deposition in most areas outside the upwelling zone are restricted to a strong eustatic latest cenomanian transgressive phase triggered by this sea level rise the omz impinged onto the north african continental shelf and the margins of intrashelf basins which mostly formed during the early cretaceous as halfgrabens important units containing c t organic rich strata in the region are the atlantic tarfaya black shales morocco western sahara black shales and phtanites in the moroccan and algerian atlas the bahloul fm in the se constantine basin and in northern and central tunisia the etel fm in the sirte basin the al hilal fm in cyrenaica libya the abu roash fm in the abu gharadig and fayium basins western desert egypt the daliyya fm along the ne sinai palestine isreal coast and the shueib fm in west central jordan

cenomanian sequence stratigraphy and sea level fluctuations in the tarfaya basin sw morocco we investigated the sequence architecture of two expanded cenomanian successions along a depth transect in the tarfaya basin sw morocco and correlated these successions to published records from northwest europe and india changes in terrigenous material carbonate and organic carbon content carbonate microfacies and foraminiferal biofacies as well as nondepositional and erosional surfaces were used to define depositional sequences and systems tracts we identified two main transgressive cycles in the lower and middle upper cenomanian separated by a major regression at the early middle cenomanian transition sequence boundary ce 3 this regressive interval is characterized by lagoonal low stand deposits indicating an overall sealevel fall of more than 30 m superimposed on the two main transgressive cycles there are 11 third order depositional sequences that correlate to globally recognized sealevel fluctuations and appear to be paced by long eccentricity variations 400 ka period positive carbon isotope excursions in the middle cenomanian 96 0 ma and latest cenomanian 94 0 ma following sealevel lowstands together with planktonic foraminiferal and ammonite datums provide a robust framework for stratigraphic correlation we suggest that the onset of these excursions was triggered by eccentricity minima during periods of low variability in obliquity nodes which probably coincided with glacioeustatic lowstands

the effect of topography on earthquake ground motion a review and new results a brief review of experimental and theoretical results about the effect of topography on seismic motion shows that they are consistent only on a qualitative basis amplification at mountain tops for wavelengths comparable with mountain widths is predicted and observed but the numerical simulations often underestimate the actual observed effects we propose that this disagreement is because current models are not complex enough we therefore computed the response to incident sh waves of a set of different complex configurations that include two dimensional surface topography with or without periodic ridges and subsurface layering the results show that 1 the topographic effect in itself is difficult to isolate from other effects like surface layering and therefore the amplification on top of geomorphologically complex sites cannot be predicted by a priori estimations based solely on topography and 2 the high crest base amplification ratio observed in the field cannot usually be matched even with complex two dimensional structures with incident plane sh waves which suggests that more complex models are needed to incorporate more complex wave fields e g sv surface and three dimensional geologic configurations

late quaternary tephrostratigraphy of baegdusan and ulleung volcanoes using marine sediments in the japan sea east sea abstract only ulleung and baegdusan volcanoes have produced alkaline tephras in the japan sea east sea during the quaternary little is known about their detailed tephrostratigraphy except for the u oki and b tm tephras trace element analysis of bulk sediments can be used to identify alkaline cryptotephra because of the large compositional contrast five sediment cores spanning the interval between the rhyolitic at 29 4 ka and aso 4 87 ka tephras were analyzed using an inaa scanning method source volcanoes for the five detected alkaline cryptotephra were identified from major element analyses of hand picked glass shards ulleung u ym and the newly identified u sado and baegdusan b j and the newly identified b sado and b ym the eruption ages of the u ym u sado b j b sado and b ym tephras are estimated to be 38 ka 61 ka 26 ka 51 ka 68 69 ka and 86 ka respectively based on correlations with regional scale tl thinly laminated layer stratigraphy produced by basin wide changes in bottom water oxygen levels in response to millennium scale paleoclimate variations this study has allowed construction of an alkaline tephrostratigraphical framework for the late quaternary linked to global environmental changes in the japan sea east sea and improves our knowledge of the eruptive histories of ulleung and baegdusan volcanoes

the crustal structure from teleseismic p wave coda i method summary the crustal structure beneath a broad band station has a strong influence on the recorded body wave coda conversely it is evident that crustal receiver effects can be employed to obtain information about the crustal structure at the receiver site in this paper we present a method to estimate the crustal receiver response and we invert the response to obtain a model of the most distinct features of the crustal structure beneath the station the crustal receiver response of a station is determined from the p wave coda of deep teleseisnic events by deconvolution with an empirically determined source wavelet this source wavelet is assumed to incorporate source attenutation and instrument effects responses obtained from clusters of events are stacked to enhance the signal to noise ratio of the data and to obtain an estimate of the variance of the data the crustal p and s velocity structure at the station is determined by non linear waveform inversion of its crustal responses an inversion strategy was developed to search efficiently for the global minimum in the misfit between data and synthetics the inversion appears to be most sensitive to large velocity constrasts in the velocity structure which give rise to high amplitude reflected and converted phases the method is illustrated by the inversion of the crustal responses of nars station ne05 it is shown that a thin layer 1 2 km of unconsolidated sediments and a strong mid crustal discontinuity at 11 km depth constitute the most prominent features of the crustal structure at this station they cause an apparent delay of the first arrival on the radial component of the seismograms and produce high amplitude sv multiples in the p wave coda

teleseismic p wave polarization analysis at the grafenberg array p wave polarization at the grafenberg array grf in southern germany is analysed in terms of azimuthal deviations and deviations in the vertical polarization using 20 yr of broad band recordings an automated procedure for estimating p wave polarization parameters is suggested based on the definition of a characteristic function which evaluates the polarization angles and their time variability as well as the amplitude linearity and the signal to noise ratio of the p wave p wave polarization at the grf array is shown to depend mainly on frequency and backazimuth and only slightly on epicentral distance indicating depth dependent local anisotropy and lateral heterogeneity a harmonic analysis is applied to the azimuthal anomalies to analyse their periodicity as a function of backazimuth the dominant periods are 180 and 360 at low frequencies between 0 03 and 0 1 hz the observed fast directions of azimuthal anisotropy inferred from the 180 periodicity are similar across the array the average fast direction of azimuthal anisotropy at these frequencies is n20 e with an uncertainty of about 8 and is consistent with fast directions of pn wave propagation lateral velocity gradients determined for the low frequency band are compatible with the moho topography of the area a more complex pattern in the horizontal fast axis orientation beneath the grf array is observed in the high frequency band between 0 1 and 0 5 hz and is attributed to anisotropy in the upper crust a remarkable rotation of the horizontal fast axis orientation across the suture between the geological units moldanubicum and saxothuringicum is observed in contrast the 360 periodicity at high frequencies is rather consistent across the array and may either point to lower velocities in the upper crust towards the bohemian massif and or to anisotropy dipping predominantly in the ne sw direction altogether p wave polarization analysis indicates the presence of layered lithospheric anisotropy in the area of the grf array seismic anisotropy is more variable in the brittle upper crust compared to lower crustal and subcrustal depths

a geochemical study of loess and desert sand in northern china implications for continental crust weathering and composition abstract chemical compositional variations of desert sands and loess loess like deposits river deposits and saline lacustrine deposits collected mostly from the southern margin of the taklimakan desert china provide strong constraints on the chemical weathering processes of continental crust and also on the provenance compositions of these quaternary deposits constant but lower concentrations of al relative to the average upper continental crust ucc in these quaternary deposits could be attributed to chemical weathering of al rich minerals such as feldspar and mica and removal of clay minerals by wind and water large variations of mobile na ca mg and sr compared to relatively immobile al k and ba resulted from the chemical weathering of plagioclase and carbonate minerals salinization and carbonation of the arid lands most trace elements are not significantly fractionated their variations in absolute concentration are caused by the dilution of quartz evaporates and carbonate minerals variations in sn concentrations probably depend on relative contents of some heavy minerals high sr ba low th u k cs ratios of the saline lake deposits suggest differences in aqueous chemistry of these elements the occurrence of the m type tetrad effect a ree pattern with four convex curves of ree compositions found mainly in the river deposits is considered the result of water particle interaction during chemical weathering of crustal materials y ho ratios of these samples are significantly higher than those of chondrite and the ucc this suggests different chemical behavior of these two elements and possibly the enrichment of carbonate materials the low lree hree feature of the saline lake deposits can be interpreted as due to the different aqueous chemical behavior of the ree s however it can also be reasonably considered as the result of inheritance from their provenance since lree and lree hree variations may be related to the geological setting of the source according to some elements that are not significantly fractionated the average provenance composition of these quaternary deposits are probably characterized by enrichments of ni cr and v over fe higher la th lower la sc and th sc and lower ta w and nb w ratios compared with the ucc composition

yield estimates of nevada test site explosions obtained from seismic lg waves a methodology is presented for determining the yield of underground nuclear explosions from lg wave amplitudes the methodology is applied to nevada test site nts explosions for which the data from short period vertical component analog seismographs at three stations are used to develop calibration curves for unsaturated material and water saturated rock source conditions the latter curves are found to provide reasonably accurate estimates of the yields of explosions in other areas of the united states and in the french sahara suggesting that they may be applicable to all continental areas if so they also can provide an estimate of the bias of mb p magnitudes between different continental sites for example the lg data from nts explosions indicate a 0 31 0 02 magnitude unit bias between nts and eastern north america similar to the approximately 0 33 unit bias found between western and eastern north america previously by use of earthquake data

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr