climate driven changes in sedimentation rate influence phosphorus burial along continental margins of the northwestern mediterranean abstract the burial of phosphorus p in continental margin sediments is a critical component of the marine reactive p budget and thus an important factor in marine biological productivity we determined downcore records of p from a site drilled on the upper slope of the gulf of lions prgl 1 northwestern mediterranean sea changes in total p content were monitored from marine isotope stage mis 6 to mis 11 in addition in two selected intervals 248 277 ka and 306 342 ka the total p record was expanded by adding detailed geochemical analyses of the various p fractions including oxyhydroxide associated p authigenic p detrital p and organic p increased sedimentation rates during glacials owing to seaward migration of the rhone s mouth enhanced the burial of reactive p oxyhydroxide associated authigenic organic phases by decreasing its time at the reactive sediment water interface in turn resulting in increasing proportion of authigenic to detrital phosphorus the inverse was found for interglacial stages the effects of glacial interglacial variation in sedimentation rate over p geochemistry resulted in changes in sediment water interface oxygenation as well as in the efficiency of p burial as shown by c p org and corg preact proxies respectively two events of high p deposition associated with authigenic p formation at 335 ka paut1 and 275 ka paut2 were associated with periods of rapid disintegration of north atlantic ice sheets leading to ice rafted debris ird deposition these high p deposition events appear to be linked to short warm periods that followed cold episodes enhanced continental runoff owing to more humid conditions during short warm episodes could play a critical role for enhanced biogenic productivity and posterior authigenic p accumulation

impact of climate variability in the western mediterranean during the last 20 000 years oceanic and atmospheric responses eolian input fluctuations and paleoceanographic conditions in the western mediterranean have been reconstructed byusing a multi proxyapproach toinferclimate variability for the last 20 000 yr a sediment core from the east alboran sea basin provides high resolution geochemical mineralogical and grain size distribution records from the last glacial maximum onward the accurate chronology obtained closely related with the north greenland ice core project has provided a detailed paleoclimate reconstruction at the centennialemillennial time scale mineral and chemical compositions as well as sediment grain size distribution have been used to establish both fluvial and eolian input variations deep water current intensity and ventilation and productivity conditions at the time of deposition during the cold period greenland stadial 2a the analyzed proxies evidence significant climate oscillations redox proxies showing marked mn al and fe al peaks as well as granulometric parameters support major changes in thermohaline circulation with active circulation triggered by the western mediterranean deep water formation ba al ratios and the presence of authigenic barite point to high productivity during the last heinrich event at this time zr al si al and ti al ratios as well as quartz and palygorskite contents also corroborate dryer conditions in the alboran borderlands with a major reorganization of atmospheric circulation at the beginningof the deglaciationand during the last heinrich event in contrast a decreasing trend in the zr al ratio and increasing mg al k al and illite chlorite kaolinite ratios would indicate enhanced river runoff and supporting lower eolian dust input and wetter periods during the bolling eallerod short term and abrupt climate oscillations such as the intra allerod cold period are likewise reflected by minor yet conspicuous changes in eolian proxies during the younger dryas we distinguish an initialcoldanddryphase withmajorwesterliesintensity thermohalinereactivation andhighproductivity

ground motion prediction of realistic earthquake sources using the ambient seismic field 1 predicting accurate ground motion is critical for earthquake hazard analysis particularly in situations where sedimentary basins trap and amplify seismic waves we exploit the information carried by the ambient seismic field to extract surface wave green s functions between seismic stations and to predict long period ground motion from earthquakes to do so we modify the surface impulse response to correct for the source depth and for the double couple focal mechanism these corrections are derived under the assumption that material properties in the immediate vicinity of the source depend only on depth using this local 1 d assumption we solve the surface wave eigenproblem and compute the fundamental mode displacement eigenfunctions to express the surface wave excitation at the source we validate this technique which we call the virtual earthquake approach by comparing computed seismograms with earthquake waveforms from four moderate earthquakes that occur near broadband stations in southern california the depth and mechanism corrections show clear improvements of the predicted ground motion relative to the surface impulse response

origin of the northern atlantic s heinrich events as first noted by heinrich 1988 glacial age sediments in the eastern part of the northern atlantic contain layers with unusually high ratios of ice rafted lithic fragments to foraminifera shells he estimated that these layers are spaced at intervals of roughly 10 000 years in this paper we present detailed information documenting the existence of the upper five of these layers in odp core 609 from 50 n and 24 w their ages are respectively 15 000 radiocarbon years 20 000 radiocarbon years 27 000 radiocarbon years about 40 000 years and about 50 000 years we also note that the high lithic fragment to foram ratio is the result of a near absence of shells in these layers although we are not of one mind regarding the origin of these layers we lean toward an explanation that the heinrich layers are debris released during the melting of massive influxes of icebergs into the northern atlantic these sudden inputs may be the result of surges along the eastern margin of the laurentide ice sheet

basin scale green s functions from the ambient seismic field recorded by meso net stations seismic waves propagating through the earth can be significantly affected by velocity structures such as sedimentary basins we investigate the propagation characteristics of seismic waves across the kanto basin japan using green s functions extracted from the ambient seismic field we use two stations situated on the eastern and southern edges of the basin as virtual sources and approximately 420 stations which are mainly a part of the metropolitan seismic observation network meso net as receivers using seismometers aligned along two straight lines with the virtual sources we find that several types of waves can be recovered each with different sensitivities to the layers that compose the basin we also show that after amplitude calibration the extracted green s functions can accurately simulate the seismic waves of two moderate mw 4 5 shallow earthquakes that occurred close to the virtual sources furthermore we find that the distribution of the 5 damped pseudovelocity response at a period of 6 s computed from the records of each event and the green s function waveforms have similar amplification patterns this study supports the fact that dense networks recording continuously the ambient seismic field in metropolitan areas can be used to accurately assess seismic hazard at high spatial resolution

dansgaard oeschger and heinrich event imprints in alboran sea paleotemperatures past sea surface temperature sst evolution in the alboran sea western mediterranean during the last 50 000 years has been inferred from the study of c37 alkenones in international marine global change studies md952043 core this record has a time resolution of 200 years allowing the study of millennial scale and even shorter climatic changes the observed sst curve displays characteristic sequences of extremely rapid warming and cooling events along the glacial period comparison of this alboran record with 18o from greenland ice greenland ice sheet project 2 core shows a strong parallelism between these sst oscillations and the dansgaard oeschger events five prominent cooling episodes standing out in the sst profile are accompanied by an anomalous high abundance of neogloboquadrina pachyderma sinistral which is confined to the duration of these cold intervals these features and the isotopic record reflect drastic changes in the surface hydrography of the alboran sea in association with heinrich events hl 5

rapid changes of glacial climate simulated in a coupled climate model abrupt changes in climate termed dansgaard oeschger and heinrich events have punctuated the last glacial period approximately 100 10 kyr ago but not the holocene the past 10 kyr here we use an intermediate complexity climate model to investigate the stability of glacial climate and we find that only one mode of atlantic ocean circulation is stable a cold mode with deep water formation in the atlantic ocean south of iceland however a warm circulation mode similar to the present day atlantic ocean is only marginally unstable and temporary transitions to this warm mode can easily be triggered this leads to abrupt warm events in the model which share many characteristics of the observed dansgaard oeschger events for a large freshwater input such as a large release of icebergs the model s deep water formation is temporarily switched off causing no strong cooling in greenland but warming in antarctica as is observed for heinrich events our stability analysis provides an explanation why glacial climate is much more variable than holocene climate

review of the late quaternary stratigraphy of the northern gulf of cadiz continental margin new insights into controlling factors and global implications abstract over the past decades the northern gulf of cadiz has been the focus of a wide range of late quaternary seismic and sequence stratigraphic studies either addressing the slope contourite depositional system cds or the development of the continental shelf yet high resolution seismic data bridging between these domains and age information have remained sparse this study based on new high resolution reflection seismic profiles calibrated to iodp expedition 339 sites u1386 u1387 now presents an updated stratigraphic framework that integrates for the first time the late quaternary records of the northern gulf of cadiz middle slope to shelf off the guadiana river seismic stratigraphic analysis of the stacking depocenter distribution stratal architecture and facies of the seismic sub units reveals the influence of 100 kyr sea level variations paced by milankovitch eccentricity cycles tectonics manifesting as two pulses of uplift and margin progradation sediment supply and bottom current activity this work furthermore contributes to the application and understanding of high resolution late quaternary sequence stratigraphy firstly the proposed sequence stratigraphic interpretation shows that adaptations to the basic models are required to integrate the shelf and slope record and to account for the presence of a significant alongslope bottom current controlled component secondly the results confirm that the sequences are dominantly composed of regressive deposits whereas the preservation of transgressive to highstand deposits is more irregular significantly the common assumption that successive major glacial lowstands are consistently recorded as well marked shelf wide erosional unconformities is demonstrated to be occasionally invalid as tectonics can obliterate this one to one relationship

origin and distribution of terrestrial organic matter in the nw mediterranean gulf of lions exploring the newly developed bit index the branched and isoprenoid tetraether bit index is based on the relative abundance of nonisoprenoidal glycerol dialkyl glycerol tetraethers gdgts derived from organisms living in terrestrial environments versus a structurally related isoprenoid gdgt crenarchaeol produced by marine crenarchaeota the bit index varies between 0 and 1 representing marine and terrestrial organic matter om end members respectively hopmans et al earth planet sci lett 224 107 116 2004 in this study the applicability of the bit index to trace terrestrial om is tested in combination with other organic parameters toc c n ratio 13corg total lipid and n alkane in the gulf of lions a river dominated continental margin of the western mediterranean we analyzed a variety of soils and riverbed sediments from the continent as well as surface sediments from the shelf and canyons the bit index in soils and riverbed sediments shows high values 0 9 while it varies between 0 02 and 0 83 in marine sediments decreasing seaward from the inner shelf to the slope for marine surface sediments high bit values are associated with lower 13corg values as well as higher toc contents and higher n alkane concentrations our results confirm that the bit index can be applied in coastal marine environments in order to characterize terrestrial om as proposed by hopmans et al 2004 therefore the bit index is a useful addition to the proxies presently available for studying the origin and distribution of om in continental margins and especially valuable in multiproxy studies

iceberg discharges into the north atlantic on millennial time scales during the last glaciation high resolution studies of north atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years much more frequently than the 7000 to 10 000 year pacing of massive ice discharges associated with heinrich events the calving cycles correlate with warm cold oscillations called dansgaard oeschger events in greenland ice cores each cycle records synchronous discharges of ice from different sources and the cycles are decoupled from sea surface temperatures these findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above greenland and in calving from more than one ice sheet

attenuation tomography of the western united states from ambient seismic noise 1 we show that the spatial coherency of the ambient seismic field can be used for attenuation tomography in the western united states we evaluate the real portion of the spatial coherency with an elastic geometric spreading term a bessel function and a distance dependent decay an attenuation coefficient in order to invert the spatial coherency a weight stack inversion technique is applied we recover phase velocity and attenuation coefficient maps at periods of 8 32s which correspond to the elastic and anelastic structure at crustal and upper mantle depths the phase velocity maps obtained by this method are of similar resolution to more standard two station methods the attenuation results provide an important complement to the information extracted from earthquake based tomography several geological features are easily identifiable in the attenuation coefficient maps such as the highly attenuating sedimentary basins along the west coast of the united states and the highly attenuating yellowstone region and the boundaries of the snake river plains

four climate cycles of recurring deep and surface water destabilizations on the iberian margin centennial climate variability over the last ice age exhibits clear bipolar behavior high resolution analyses of marine sediment cores from the iberian margin trace a number of associated changes simultaneously proxies of sea surface temperature and water mass distribution as well as relative biomarker content demonstrate that this typical north south coupling was pervasive for the cold phases of climate during the past 420 000 years cold episodes after relatively warm and largely ice free periods occurred when the predominance of deep water formation changed from northern to southern sources these results reinforce the connection between rapid climate changes at mediterranean latitudes and century to millennial variability in northern and southern polar regions

the 100 ka and rapid sea level changes recorded by prograding shelf sand bodies in the gulf of lions western mediterranean sea thick forced regressive units on the wide continental shelf of the gulf of lions western mediterranean recorded the composite effect of sea level changes during the quaternary they are mostly composed of coastal siliciclastic and bioclastic wedges showing clinoform geometry these deposits have been intensively explored through high resolution seismic investigations but only recently it was possible to ground truth seismic interpretations based on a long 100 m borehole that crossed the succession and recovered a large part of the mainly sandy deposits similar to 84 recovery a multiproxy analysis of the sedimentary succession shows that 1 the stratal architecture of the shelf margin is defined by major bounding surfaces that are polygenic erosion surfaces associated with coarse grained material incorporating abundant and diverse shells including cold water fauna presently absent from the mediterranean sea between each surface coarsening upward units with steep up to 5 degrees foresets are made of massive more than 20 m thick sands with possible swaley and hummocky cross stratification passing seaward to sands with muddy intervals and further offshore alternating highly boiturbated sands and silts each prograding wedge corresponds to a forced regressive shoreface or delta front prodelta deposited during the overall sea level falls occurring at relatively slow interglacial glacial transition and therefore represents the record of 100 ka cyclicity higher frequency milankovitch cyclicities are also probably represented by distinct shoreface delta front wedges 2 detailed examination of the architecture and chronostratigraphy of the most recent sequence shows that minor bounding surfaces corresponding to abrupt shallowing of sedimentary facies separate downward stepping parasequences within the last 100 ka sequence

imaging the upper crust of the korean peninsula by surface wave tomography cross correlation of seismic background motions campillo and paul 2003 shapiro et al 2005 is applied to observations from the korean meteorological administration seismic network to estimate the short period rayleigh and love wave dispersion characteristics of the region standard processing procedures are applied to the cross correlation except that signal whitening is used in place of one bit sampling to equalize power in signals from different times multiple filter analysis is used to extract the group velocities from the estimated green s functions which are then used to image the spatially varying dispersion at periods between 0 5 and 20 sec the tomographic inversion technique used inverts all periods simultaneously to provide a smooth dispersion curve as a function of period in addition to the usual smooth spatial image for a given period the gyeongsang basin in the southeastern part of the peninsula is clearly resolved with lower group velocities

centroid single force inversion of seismic waves generated by landslides the centroid moment tensor cmt waveform inversion method of dziewonski et al 1981 is modified to analyze long period seismic waves generated by single force events such as the gigantic landslides associated with the 1980 eruption of mount st helens we refer to the method as centroid single force csf inversion as the result of the inversion we obtain the spatio temporal centroid and three components of a vector we call the csf vector which is the seismic point source representation of a landslide and whose direction is the opposite of the direction of sliding the sealer magnitude of the csf vector measures the overall size of the landslide and is given by mcsf md where m is the mass of the sliding object and d is the sliding distance we apply csf inversion to the long period surface waves generated by the 1980 mount st helens event the 1975 kalapana earthquake and the 1974 mantaro landslide using seismograms from the gdsn ida and hglp networks the csf solution for the st helens event is remarkably consistent with the actual geological observations and proves the efficacy of csf inversion the csf solution for the kalapana event does not fit the overall waveforms better than the cmt solution does however because the cmt solution does not explain the observed love wave radiation pattern it may be necessary to invoke a combination of both types of mechanism for this event although the geometry of the csf solution the direction of the force for the mantaro event is consistent with the actual landslide mcsf is about 5 times smaller than that expected from the mass and travel distance of the landslide estimated by geological observations this discrepancy may suggest either the relatively aseismic nature of this landslide or that the total volume of the slide was overestimated by analogy to single station cmt inversion single station csf inversion also appears to be stable and useful

earthquake ground motion prediction using the ambient seismic field 1 the waves generated by faulting represent the primary threat posed by most large earthquakes the effect of complex geological structures such as sedimentary basins on earthquake ground motion is a source of particular concern we show that it is possible to extract reliable phase and amplitude response that includes the effects of complex structure for the elastodynamic green s function from the ambient seismic field using deconvolution we demonstrate the accuracy of the approach by predicting complex ground motion for a moderate mw 4 6 earthquake in southern california as recorded in the los angeles basin this suggests a novel approach to seismic hazard analysis in which ground motion from hypothetical future earthquakes is simulated directly without the need for modeling the detailed heterogeneity of the earth s crust as an intermediate step

late quaternary deltaic lowstand wedges on the rhone continental shelf france abstract shallow seismic profiles on the rhone continental shelf have shown the existence of stacked progradational lowstand wedges on the outer shelf accumulated during late quaternary glacioeustatic lowstands the wedges are bounded by sharp to erosional sequence boundaries and onlap onto the middle shelf the thickness of individual wedges attains 50 meters at the shelf edge where they are sheared by slumping the wedges exhibit well developed progradational clinoforms episodically interrupted by internal unconformities on which there is a downward shift of the succeeding clinoforms these represent small scale in the order of a few meters falls in sea level during the quaternary eustatic cycles the durations of the stable highstand conditions appear to have been too brief to permit the regressive highstand tract to prograde to the outer shelf therefore the shelf edge builds up entirely with lowstand wedges

moment tensors of ten witwatersrand mine tremors ground motions recorded both underground and on the surface in two of the south african gold mining districts were inverted to determine complete moment tensors for 10 mining induced tremors in the magnitude range 1 9 to 3 3 the resulting moment tensors fall into two separate categories seven of the events involve substantial coseismic volumetric reduction v together with normal faulting entailing shear deformation ad where the summation is over fault planes of areaa and average slipd for these events the ratio v ad ranges from 0 58 to 0 92 with an average value of 0 71 for the remaining three events v is not significantly different from zero these events are largely double couple sources involving normal faulting surprisingly the two types of source mechanism appear to be very distinct in that there is not a continuous distribution of the source mix from v 0 to v ad presumably the coseismic closure indicates substantial interaction between a mine stope and adjacent shear failure in the surrounding rock under the influence of an ambient stress for which the maximum principal stress is oriented vertically

a discontinuous climatic record from 187 to 74 ka from a speleothem of the clamouse cave south of france this study presents a continental paleoclimatic record in the south of france based on n 18 o n 13 c and the 234 u 238 u activity ratio dated by the 230 th 234 u disequilibrium method with thermal ionization mass spectrometry a stalagmite cla4 from the clamouse cave offers a discontinuous stable isotopic record between 189 ka and 74 ka which covers marine isotope stages mis 7 6 4 5 5 5 3 and 5 1 the growth phases of the cla4 stalagmite correspond to high sea level stages except during mis 6 4 169 162 ka all the growth phases of cla4 correspond to humid periods corresponding to the sapropel events observed in the eastern mediterranean basin thus the influence of a strong hydrological activity in the eastern mediterranean basin during these periods prevailed as far west as the south of france because the karstic system studied strongly buffers the isotopic composition of water isotopic variations of the calcite deposited in the cave represent mainly global and large scale environmental variations when isotopic equilibrium conditions prevailed for calcite crystallization sub stage 5 3 the end of 5 5 and mis 7 were colder by about 4 6 c calculated temperature compared to present day temperature while the growth phases of substages 5 1 and the beginning of 5 5 reflect environmental conditions close to present ones the n 18 o and n 13 c values of cave deposits of the sub stage 6 4 are 1 strongly marked by kinetic fractionation processes such as evaporation due to moisture deficit within the cave atmosphere during the first step of this growth phase and 2 related to higher humidity due to a second period of enhanced rainfall during the second step of growth this study shows that even if calcite has not been deposited at isotopic equilibrium its isotopic composition can give insights into the environmental conditions at the time of deposition 2002 elsevier science b v all rights reserved

long period ground motion simulation of a subduction earthquake using the offshore onshore ambient seismic field large earthquakes that occur in subduction zones are likely to generate long period ground motions that can cause severe damage even at great distances from the epicenter we extracted surface to surface impulse response functions from the ambient seismic field recorded by offshore ocean bottom seismometers located atop the nankai subduction zone and onshore stations we showed that these offshore onshore impulse response functions can be used to accurately simulate the long period ground motions generated by an offshore moderate subduction earthquake moreover we also found that the distributions of the earthquake and impulse response function pseudovelocity response spectra have similar maximum amplifications in the same area close to the earthquake epicenter this suggests that the ambient seismic field recorded by the increasing number of ocean bottom seismometers around the world can be used to assess seismic hazard related to offshore subduction earthquakes without prior knowledge of the velocity structure

climate forcing and neanderthal extinction in southern iberia insights from a multiproxy marine record abstract paleoclimate records from the western mediterranean have been used to further understand the role of climatic changes in the replacement of archaic human populations inhabiting south iberia marine sediments from the balearic basin odp site 975 was analysed at high resolution to obtain both geochemical and mineralogical data these data were compared with climate records from nearby areas baexcces was used to characterize marine productivity and then related to climatic variability since variations in productivity were the consequence of climatic oscillations climate productivity events have been established sedimentary regime primary marine productivity and oxygen conditions at the time of population replacement were reconstructed by means of a multiproxy approach climatic oceanographic variations correlate well with homo spatial and occupational patterns in southern iberia it was found that low ventilation u th high river supply mg al low aridity zr al and low values of baexcess coefficient of variation may be linked with neanderthal hospitable conditions we attempt to support recent findings which claim that neanderthals populations continued to inhabit southern iberia between 30 and 28 ky cal bp and that this persistence was due to the specific characteristics of south iberian climatic refugia comparisons of our data with other marine and continental records appear to indicate that conditions in south iberia were highly inhospitable at 24 ky cal bp thus it is proposed that the final disappearance of neanderthals in this region could be linked with these extreme conditions

catastrophic arid episodes in the eastern mediterranean linked with the north atlantic heinrich events the response of continental climate to the well documented climate oscillations during the last glacial period has been a subject of intense interest yet much less is known about the influence on regional continental climates than in the marine or polar realms of earth the detailed lake level history of the closed lake lisan paleo dead sea in the middle east has been reconstructed from shoreline indications and high resolution u th and 1 4 c chronologies thus providing data on the response of the lake s catchment area to the climate changes during the corresponding period we present a correlation between the newly developed lake lisan level curve for the past 55 k y and the north atlantic heinrich events the correlation indicates a closely connected climate response between these north atlantic events and the hydrologic conditions that prevailed in the eastern mediterranean our findings show that although the generally cooler conditions that prevailed during the last glaciation favored high levels of the lake catastrophic events in the north atlantic which are associated with maximum cooling have been responsible for droughts in the eastern mediterranean we infer that cold water input to the mediterranean originating in the collapse of the north atlantic deep water circulation caused the reduction of evaporation and less precipitation in the eastern mediterranean

an implosive component in the seismic moment tensor of a mining induced tremor in early 1988 a special study in one of the major south african gold fields yielded seismograms that indicate seismic moment tensors having substantial implosive components the moment tensor resulting from the inversion of the ground motion data from the best recorded event was decomposed into isotropic and deviatoric components from which both the coseismic volumetric closure v and the total shear deformation ad where a is fault area and d is average slip could be estimated the finding here that v ad is consistent with earlier analyses of how the tabular mine stopes interact with the surrounding rock mass to produce seismic deformation

a millennial scale u37k sea surface temperature record from the south china sea 8 n over the last 150 kyr monsoon and sea level influence we report 150 kyr records of u37 sea surface temperature sst and carbonate content with 150 200 year sampling resolution from the southern south china sea scs in the northern margin of the western pacific warm pool wpwp using images core md972151 the glacial interglacial sst change is about 5 c for termination ii 23 5 to 28 5 c and 4 c for termination i 24 to 28 c the simultaneous rise of sea level and u37 sst during termination i suggests that sea level change has played an important role in the scs sst variability by influencing the exchange of tropical ocean warm surface water with the scs through the sunda shelf region sill depth 30 50 m when sea level drop was less than 30 m relative to today s md972151 sst was constantly above 27 c a situation which occurred during mis 5e part of mis5c and 5a and over the last 11 kyr sea level change was also the main control on carbonate content in the scs this was lower during low sea level stands due to the dilution effect of enhanced terrigenous inputs within the limitations of our age model millennial scale sst oscillations 1 5 c over a few hundred years occurred frequently during the entire glacial period correlating reasonably well with the hulu monsoon record from eastern china and the dansgaard oeschger d o cycles recorded for high latitude regions in the northern hemisphere such correlations suggest a possible teleconnection between higher latitude atmospheric forcing and low latitude climate oscillations in the western pacific tropical region via the asian monsoon system carbonate content also reveals millennial scale oscillations during the glacial period with higher content correlated with higher sst millennial scale fluctuations of sst and carbonate contents at this low latitude scs provide additional evidence that high frequency climate changes are global phenomena

phase relationships between millennial scale events 64 000 24 000 years ago a core recovered on the iberian margin off southern portugal can be correlated with greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over greenland our age model identifies the base of every interstadial between 64 000 and 24 000 years ago and uses the greenland ice core project grip timescale the oxygen isotope signal in benthic foraminifera on this grip based timescale is quite different from the planktonic record and resembles the temperature record over antarctica when this is synchronized with greenland using the record of methane in the atmospheric air in the polar ice cores we interpret the benthic record as indicating significant fluctuations in ice volume during millennial events and we suggest that antarctic temperature changed as a function of ice volume

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

shoreface migrations at the shelf edge and sea level changes around the last glacial maximum gulf of lions nw mediterranean the bourcart herault canyon interfluve in the gulf of lions nw mediterranean was the site of very high sedimentation up to 2 5 m kyr around the last glacial maximum due to the vicinity of major fluvial systems that fed the shelf edge shoreface deposits and offshore muds deposited during each glacial interglacial 100 kyr cycle created a repeated motif with high angle and low angle clinoforms on seismic profiles new detailed morphological sedimentological and paleo environmental data constrained by 14c dating allow us to propose a scenario for the evolution of this critical area between 46 and 15 cal kyr bp the major seismic sequence s5 formed as a forced regression during the overall sea level fall between mis 3 and mis 2 can be sub divided into several prograding units which indicate that relative sea level changes were punctuated by intervals of increased fall or slow down or even stillstand similarly the onset of sea level rise was marked by steps during which wave cut terraces formed and can be tracked all around the gulf of lions three stillstands or slow downs of sea level change are identified and dated by deposits found at 90 m relative sea level 21 cal kyr bp 110 115 m rsl 18 17 cal kyr bp and 98 105 m rsl before 15 9 cal kyr bp cementation of beach rocks that now form eroded pinnacles culminating at 90 m occurred during the 21 kyr stillstand the position of relative sea level during the maximum lowstand is not known but should be deeper than 115 m periods of increased northwesterly winds favoured transport of coarser sediment at the shelf edge in relation with deep water cascading this created a distinct sandy interval during the period of heinrich event 2 around 24 cal kyr bp at the origin of amplitude anomaly on very high resolution seismic data the increased sea level rise around 15 cal kyr bp resulted in an abrupt decrease of sedimentation

impact of climate and sea level changes on the ventilation of intermediate water and benthic foraminifer assemblages in the gulf of lions off south france during mis 6 and 7 abstract benthic and planktic foraminifer assemblages together with oxygen stable isotope were studied in the prgl1 borehole promess1 drilled on the upper slope of the gulf of lions with a view to reconstruct the impact of climate changes on surface and bottom waters between mis7 and mis6 foraminifer species were grouped by r mode principal components analysis we obtained 3 factors in benthic assemblages that were related to eutrophic mesotrophic and oxygenated environments in the planktic foraminifer assemblages four factors were considered that explained the changes of sea surface temperature productivity and turbulence in the water column variations in the terrestrial organic carbon supply associated with eustatic sea level changes mainly controlled oxygen consumption and the benthic communities during mis7 the benthic communities were mainly mesotrophic owing to the low supply of terrestrial organic carbon because the coastline was distant from the slope however during mis6 the sea level drop caused a rapid progradation of the river rhone prodelta and dramatically increased the supply of terrestrial organic carbon resulting in a pronounced increase in eutrophic foraminifers apart from the effect of the river discharge which contributed to the reduced oxygen content we recognized periods of intense bottom ventilation during mis 6 and to a lesser extent in the substadial stages of mis 7 the ventilation events are well matched by higher turbulence and convection in the water column during cold episodes associated with an intensification of the northwesterlies in contrast during the short millennial scale warming events of mis6 the stratification of the water column rapidly reduced bottom ventilation these results are consistent with those reported in previous studies that point to enhanced dense water formation in the gulf of lions during cold stages

long period seismic amplification in the kanto basin from the ambient seismic field tokyo like many seismically threatened cities is situated atop a sedimentary basin that has the potential to trap and amplify seismic waves from earthquakes we study amplification in the kanto basin by exploiting the information carried by the ambient seismic field we use 375 seismic stations from the high sensitivity seismograph network across central honshu as virtual sources and 296 seismic stations of the metropolitan seismic observation network shallow borehole seismometers within the basin as receivers to map the basin response we find a linear relationship between ground motion and basin depth at periods of 2 10 s that could be used to represent 3 d basin effects in ground motion prediction equations we also find that the strength of basin seismic amplification depends strongly on the direction of illumination by seismic waves

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

western mediterranean planktonic foraminifera events and millennial climatic variability during the last 70 kyr abstract detailed study of associations of planktonic foraminifera in cores md95 2043 and odp 977 located in the alboran sea mediterranean sea has allowed the identification of 29 new faunal events defined by abrupt changes in the abundances of neogloboquadrina pachyderma right and left coiling turborotalita quinqueloba globorotalia scitula globorotalia inflata globigerina bulloides and globigerinoides ruber white and pink varieties the age model for odp 977 was based on that of md95 2043 cacho et al 1999 paleoceanogr 14 698 705 on the isotopic stratigraphy and on two ams 14c measurements sea surface temperatures ssts were estimated for the last 54 kyr using the modern analog technique mat and were compared with the ssts provided by the uk 37 method the uk 37 record is very similar to the mat annual mean temperature record for the last 8 kyr however for older times alkenone derived temperatures are consistently higher than the annual mat temperatures this offset may be due to an underestimation of the sst provided by the planktonic foraminiferal method for glacial times to an overestimation of the uk 37 record or to changes in the seasonal production of alkenones most of the variability in the fauna is related to the millennial variability of heinrich and dansgaard oeschger d o events during heinrich events hes and most of the other d o stadials g bulloides t quinqueloba and g scitula increased while n pachyderma right coiling g inflata and g ruber decreased by contrast n pachyderma left coiling was only abundant in the hes the main component of the associations n pachyderma right coiling follows a general trend similar to that of sea level and 18o this species reached its highest abundance during the last glacial maximum when sea level was at a lower position the occurrence of a shallower nutricline owing to a shallowing of the interface between atlantic inflowing and mediterranean outflowing waters could have favoured the development of neogloboquadrinids in the vicinity of the strait of gibraltar

changes in planktic and benthic foraminifer assemblages in the gulf of lions off south france response to climate and sea level change from mis 6 to mis 11 1 a multidisciplinary study involving micropaleontological and geochemical tools was carried out in borehole prgl1 promess 1 with the aim of reconstructing the impact of climate change and sea level variation between 133 ka and 406 ka in the upper slope of the gulf of lions we used factor analysis to obtain three main benthic assemblages related to eutrophic mesotrophic and oxygenated environments planktic foraminifers were grouped as warm water and cold turbulent species these results were compared with records of caco3 and major and trace elements al ca k sr as well as the c n ratio of organic matter power and cross spectral analysis showed a straightforward relationship between precession minima and thermal stratification of the water column as well as the occurrence of eutrophic bottom conditions during lowstand periods and mesotrophic environments at times of highstand these eutrophic mesotrophic oscillations usually driven by global eustatic change also involved regional variations in caco3 source to this environment during periods of precession maxima enhancement of northwesterly winds increased primary productivity by mixing enhancing the percentage of cold turbulent species in the water column and the proportion of oxygenated benthic species on the bottom during interglacial stages these events were recorded by lower biogenic carbonate at the expense of higher silicate related components most likely due to a higher supply from pyrenees rivers the record of oxygenated benthic species can be a good proxy to monitor past changes in winter intermediate water dynamics driven by northwesterly winds

synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the mediterranean region land sea climatic proxies have been obtained from the last glacial section of images core md95 2043 western mediterranean sea vegetation and alkenone derived sst curves indicate rapid 150 years and synchronous terrestrial and marine climatic changes paralleling the dansgaard oeschger d o climatic variability over greenland this frequency of climate change can be related to shifts between the two modes of operation of the north atlantic oscillation nao transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during heinrich events hes in comparison with other d o stadials the development and persistence of both scandinavian and atlantic mobile polar highs over southwestern europe may explain the extreme cooling 10 c and dryness 400 mm during heinrich events 5 and 4 in the mediterranean region comparison of the results of core md95 2043 with similar climatic data from images core md95 2042 located off portugal indicates that thermal and precipitation gradients occurred between the mediterranean and the atlantic sides of iberia within hes hes 4 and 5 are associated with more humid conditions in the atlantic by 200 mm than in the mediterranean site as is the case at the present time this comparison also illustrates the different behaviour of these areas during the d o stadials in contrast with the mediterranean site the atlantic site shows similar precipitation and temperature drops for all the d o stadials including those related to the hes here we propose the operation of different mobile polar highs mph as the driving mechanism for this difference in behaviour between the atlantic and mediterranean sides of iberia hes are related to a stronger influence of the scandinavian mph forcing a severe aridification and cooling of the full iberian peninsula the atlantic mph may have been dominant during the other stadials which would preferentially affect southwestern iberia

climatic and hydrologic variability in the northern mediterranean across the onset of the messinian salinity crisis abstract the youngest and one of the largest saline deposits of earth history formed in the mediterranean during the messinian salinity crisis msc 5 97 5 33 ma late miocene when global climate was experiencing a trend of cooling and aridification however recent paleoclimate reconstructions indicate strong climate gradients across the mediterranean basin and the persistence of humid conditions in the northern mediterranean during the earliest phase of the msc to characterize climatic and hydrologic variability across the onset of the msc we studied inorganic geochemical proxies comprising si ti and zr element distributions and organic geochemical proxies such as sedimentary plant wax contents and their carbon 13cn alk and hydrogen 2 n alk stable isotope compositions in deep water 200 m alternating shale and marl deposits of the piedmont basin govone section nw italy our results suggest that deposition was controlled by precession driven climate fluctuations before and after the onset of the msc with shales deposited under moister conditions lower element al ratios and 2 n alk values and marls when drier conditions prevailed higher element al ratios and 2 n alk values the observed 2 n alk pattern further suggests changes in the relative contributions of the sources of moisture for precipitation at precession minima shales were deposited and moisture was mainly sourced from the north atlantic as reflected by lower 2 n alk values at precession maxima marls were deposited and higher 2 n alk values point to a probably western mediterranean source of moisture the decrease of element al ratios as well as the coeval increase of plant wax abundances after the onset of the msc indicate enhanced humidity and increased net precipitation over the northern mediterranean these changes coincided with a restriction of the atlantic mediterranean gateways and resulted from an enhanced contribution of deuterium enriched moisture sourced from seawater evaporation in the mediterranean evidenced by an increase of 2 n alk values

the response of sst to insolation and ice sheet variability from mis 3 to mis 11 in the northwestern mediterranean sea gulf of lions here we present a sea surface temperature sst record based on the uk 37 index from the prgl1 borehole promess1 drilled on the upper slope of the gulf of lions gl this is the first continuous and high resolution record in the northwestern mediterranean sea from marine oxygen isotope stage 3 mis 3 to mis 11 due the location of the gl the sst proxy can be considered to be a reliable tool to study the climate link between high latitude and midlatitude during glacial inceptions the northern ice sheet signal via cold northwesterly winds was first recorded in our study area in comparison with southern locations highlighting the strong sensitivity of this location to high latitude dynamics moreover the amplitude of the millennial scale variability in the western mediterranean basin seems to be the result of both ice sheet and insolation variability

oceanic processes as potential trigger and amplifying mechanisms for heinrich events marine sediments recorded a series of heinrich events during the last glacial period massive ice surges thatdeposited prominent layers of ice rafted debris in the north atlantic here we explore oceanic mechanisms thatcan potentially trigger and amplify the observed ice calving events simulations of abrupt glacial climate changewith a coupled ocean atmosphere sea ice model show a substantial regional sea level rise in the north atlantic inresponse to a collapse of the atlantic meridional overturning circulation moc the increased heat uptake ofthe global ocean after the moc collapse leads to an additional rise in global sea level we hypothesize that thesesea level changes have the potential to destabilize northern hemisphere ice shelves and ice sheets and to triggerice surges sea level rise due to ice calving and subsurface ocean warming provides two positive feedbackmechanisms contributing to further destabilization of ice shelves and ice sheets

sedimentary sequences in the gulf of lion a record of 100 000 years climatic cycles abstract the wide continental shelf of the gulf of lion up to 70 km has been the object of numerous investigations since the early days of oceanography yet the question of sequences duration the mechanisms of deposition and factors implied remained unanswered a study of a very dense grid of very high resolution vhr seismic reflection sparker data associated with surficial cores both collected by ifremer between 1992 and 2001 on the outer shelf and upper slope offshore of sete in the languedoc region gives a new insight into these issues analysis of the 3d geometry of the sedimentary record reveals a basic depositional pattern consisting of a pair of horizontally juxtaposed and downlapping prisms prism pi with low angle clinoforms results obtained from integrating lithology palynology micropaleontology seismic stratigraphy stratigraphic simulation support the hypothesis that the basic depositional pattern records a 100 000 years glacioeustatic interglacial glacial cycle as previously suggested by aloisi aloisi j c 1986 sur un modele de sedimentation deltaique contribution a la connaissance des marges passive these de doctorat d etat universite de perpignan 162 pp prisms pi corresponds to deposition at high sea level and prisms pii to deposition during low sea level at glacial maxima five sequences of paired prisms capped by five major erosion surfaces have been identified and modelled showing that the corresponding glacioeustatic cycles the last five cycles at least are recorded on the shelf of the western part of the gulf of lion

moment tensor inversion of induced microseisnmic events evidence of non shear failures in the 4 m 2 moment magnitude range to assess objectively the source mechanism of mining induced seismic events we developed an algorithm to invert for the moment tensor components from this inversion the ratio of isotropic deviatoric component in the source is obtained we are applying this method to microseismic events 4 m 2 recorded at the underground research laboratory url in pinawa manitoba where a tunnel is being excavated at 420 m depth to monitor the seismic activity induced by this opening an array of 16 triaxial accelerometers was installed around the planned tunnel results from the moment tensor inversion on a fist data set provide evidence of non shear failure mechanisms furthermore the location of events displaying a tensile component corresponds to a breakout observed underground in the roof of the tunnel

abrupt climate changes how freshening of the northern atlantic affects the thermohaline and wind driven oceanic circulations leading hypotheses for abrupt climate changes are focused on the ocean response to a freshening of surface waters in the north atlantic the degree to which such a freshening affects the deep slow thermohaline rather than the shallow swift wind driven circulations of the ocean and hence the degree to which that freshening affects climate in high rather than low latitudes differ from model to model depending on factors such as the treatment of diffusive processes in the oceans many comprehensive climate models are biased and confine the influence mainly to the thermohaline circulation and northern climates simulations of paleoclimates can provide valuable tests for the models but only some of those climates provide sufficiently stringent tests to determine which models are realistic

glacial to holocene terrigenous organic matter input to sediments from orca basin gulf of mexico a combined optical and biomarker approach in this study we assessed changes in the contribution of terrigenous organic matter om to the gulf of mexico over the course of the last deglaciation the last 25 kyr to this end we combined optical kerogen analyses with bulk sedimentary biomarker and compound specific carbon isotope analyses samples were obtained from core md02 2550 from orca basin 2249 m water depth at 26 56 77n 91 20 74w with temporal resolution ranging from multi decadal to millennial scale depending on the proxy all proxies confirmed larger terrigenous input during glacial times compared to the holocene in addition the kerogen analyses suggest that much of the glacial om is reworked at least 50 of spores and pollen grains and 40 of dinoflagellate cysts the holocene sediments in contrast contain mainly marine om which is exceptionally well preserved during the deglaciation terrigenous input was generally high due to large meltwater fluxes whereby discrepancies between different proxies call for additional influences such as the change in distance to the river mouth local productivity changes and hydrodynamic particle sorting it is possible that kerogen particles and the terrigenous biomarkers studied here represent distinct pools of land derived om with inputs varying independently

late glacial to preboreal sea level rise recorded by the rhone deltaic system nw mediterranean abstract a unique late glacial preboreal record of changes in sea level and sediment fluxes originating from the alps is recorded in the rhone subaqueous delta in the western mediterranean sea the compilation of detailed bathymetric charts together with high resolution seismic profiles and long cores reveals the detailed architecture of several sediment lobes related to periods of decreased sea level rise and or increased sediment flux they are situated along the retreat path of the rhone distributaries from the shelf edge and canyon heads up to the modern coastline they form transgressive backstepping parasequences across the shelf the late holocene highstand deltas being confined to the inner shelf the most prominent feature is an elongated paleo shoreface deltaic system with an uppermost sandy fraction remolded into subaqueous dunes a long piston core into the bottomsets of this prograding unit allows precise dating of this ancient deltaic system in seismic data it displays aggradation starting at 15 cal kyr bp followed by progradation initiated during the first phase of the younger dryas a period of reduced sea level rise or stillstand the delta kept pace with resumed sea level rise during the preboreal which is estimated at about 1 cm yr as a result of increased sediment supply from the alps melting of glaciers and more humid climate flushing the sediment down to the sea abandonment of the delta occurred around 10 500 cal yr bp that is to say about 1000 yr after the end of the younger dryas probably because of decreased sediment flux

sand bodies at the shelf edge in the gulf of lions western mediterranean deglacial history and modern processes abstract the outer continental shelf of the gulf of lions is covered by thick mainly regressive sand deposits a combination of seismic sedimentological and geochronological methods allows us to demonstrate that a veneer of transgressive sand bodies few m to less than 1 m thick reworks these deposits they take the form of sand ridges and transverse dunes that formed at different periods in fact the low gradient outer shelf of the gulf of lions displays a complete record of deglacial history including not only transgressive deposits that formed during sea level rise but also bedforms that still evolve under episodic high energy events that occur under more highstand conditions core lithology 14 c dates and regional sea level curve suggest that the formation of the sand ridges was favoured during a period of deceleration of sea level rise such as during the younger dryas event the dunes are part of a mobile carpet here u160 the deposition of this marine sand veneer is possibly related to the interplay between different factors that trigger the turning on off for bottom currents sand deposition transport on the outer shelf in fact the sands appear to have been reworked intermittently due to high energy conditions in shallow water depth currents wave regime and wind driven circulation as well as they form current ridges superimposed to the transgressive deposits in the westernmost part of the studied area at the bourcart canyon s head

surface wave tomography from ambient seismic noise of accelerograph networks in southern korea 1 an efficient and robust cross correlation technique for estimation of surface wave green s function between two locations is applied to a set of ambient noise data recorded by accelerograph networks in the southern korea we have estimated 1843 group velocities of rayleigh waves in the period band of 2 4 seconds from correlation pairs of 91 accelerograph stations relatively dense and uniform coverage of the pairs provides us with high resolution tomographic image of surface wave group velocities in the region the resulting group velocity distribution correlates well with the characteristic features of geological map of the region displaying low velocities for the sedimentary basins and regions of volcanic and metasedimentary rocks and high velocities for the regions where granitoid basement rocks outcrop the short period information from the accelerograph network can enhance resolution of the subsurface structures at depths within a few kilometers which may be predominantly responsible for simulation results of strong ground motions

broadband ambient noise surface wave tomography across the united states 1 this study presents surface wave dispersion maps across the contiguous united states determined using seismic ambient noise two years of ambient noise data are used from march 2003 through february 2005 observed at 203 broadband seismic stations in the us southern canada and northern mexico cross correlations are computed between all station pairs to produce empirical green functions at most azimuths across the us coherent rayleigh wave signals exist in the empirical green functions implying that ambient noise in the frequency band of this study 5 100 s period is sufficiently isotropically distributed in azimuth to yield largely unbiased dispersion measurements rayleigh and love wave group and phase velocity curves are measured together with associated uncertainties determined from the temporal variability of the measurements a sufficient number of measurements 2000 is obtained between 8 and 25 s period for love waves and 8 and 70 s period for rayleigh waves to produce tomographic dispersion maps both phase and group velocity maps are presented in these period bands resolution is estimated to be better than 100 km across much of the us from 8 40 s period for rayleigh waves and 8 20 s period for love waves which is unprecedented in a study at this spatial scale at longer and shorter periods resolution degrades as the number of coherent signals diminishes the dispersion maps agree well with each other and with known geological and tectonic features and in addition provide new information about structures in the crust and uppermost mantle beneath much of the us

investigating the capability to extract impulse response functions from ambient seismic noise using a mine collapse event using recordings of a mine collapse event mw 4 2 in south korea in january 2015 we demonstrated that the phase and amplitude information of impulse response functions irfs can be effectively retrieved using seismic interferometry this event is equivalent to a single downward force at shallow depth using quantitative metrics we compared three different seismic interferometry techniques deconvolution coherency and cross correlation to extract the irfs between two distant stations with ambient seismic noise data the azimuthal dependency of the source distribution of the ambient noise was also evaluated we found that deconvolution is the best method for extracting irfs from ambient seismic noise within the period band of 2 10 s the coherency method is also effective if appropriate spectral normalization or whitening schemes are applied during the data processing

analysis of exceptionally large tremors in two gold mining districts of south africa an investigation of ground motion recorded using broad band wide dynamic range digital seismographs of large mine tremors from two south african mining districts with different geologic settings reveals some essential differences in both seismic source and ground motion parameters in the klerksdorp district where the strata are offset by major throughgoing normal faults the largest tremors with magnitudes ranging as high as 5 2 tend to be associated with slip on these pre existing faults moreover the seismic source and ground motion parameters are quite similar to those of natural crustal earthquakes in the carletonville district by contrast where substantial faults do not exist the large magnitude tremors appear to result from the failure of relatively intact rock and cause seismic stress drops and ground motion parameters higher than normally observed for natural shocks additionally there appears to be an upper magnitude limit of about 4 in the carletonville district detailed analyses of an exceptionally large event recorded locally from each of these districts serve to highlight these contrasts

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

climatic conditions during marine oxygen isotope stage 6 in the eastern mediterranean region from the isotopic composition of speleothems of soreq cave israel at several times during marine oxygen isotope stage 6 the eastern mediterranean region was influenced by two extreme climatic systems the large ice sheet over northern europe and the wet tropics associated with african monsoons during this interval two major climatic events occurred in the region the sapropel s6 layer formed ca 176 ka in the eastern mediterranean basin owing to the increase in the african monsoon and another event although not large enough to form sapropel occurred ca 151 ka the isotopic composition of soreq cave speleothems seems to record these events as very low 18 o 13 c values dated as ca 178 and 152 ka the very low 18 o 13 c values of 6 and 11 to 12 respectively are typical of interglacial intervals but here they were recorded during a glacial interval such low peaks indicate that in this part of the eastern mediterranean region i e israel the rainfall amount increased dramatically moreover the isotopic record of the speleothems also shows that during the entire stage 6 although the climate was as cold as much of the last glacial the conditions were never as dry

anelastic earth structure from the coherency of the ambient seismic field 1 cross correlation of the ambient seismic field is now routinely used to measure seismic wave travel times however relatively little attention has been paid to other information that could be extracted from these signals in this paper we demonstrate the relationship between the spatial coherency of the ambient field and the elastodynamic green s function in both time and frequency domains through measurement of the frequency domain coherency as a function of distance we sequentially recover phase velocities and attenuation coefficients from these measurements we generate 1 d shear wave velocity and attenuation models for southern california the ambient field measurements of attenuation and the exceptional path coverage that results from the many possible interstation measurements allow us to extend q estimates over a range of frequencies that has previously been difficult to analyze using earthquake data measurements from paths that cross major sedimentary basins show both lower wave speeds and lower quality factors than other paths as expected our results indicate that there is a wealth of information available in the spatial coherency of the ambient seismic field

evidence of abrupt changes in western mediterranean deep water circulation during the last 50kyr a high resolution marine record from the balearic sea abstract the images core md99 2343 recovered from a sediment drift north of the island of minorca in the north western mediterranean sea holds a high resolution sequence that is perfectly suited to study the oscillations of the overturning system of the western mediterranean deep water wmdw detailed analysis of grain size and bulk geochemical composition reveals the sensitivity of this region to climate changes at both orbital and centennial millennial temporal scales during the last 50 kyr the dominant orbital pattern in the k al record indicates that sediment supply to the basin was controlled by the insolation evolution at 40 n which forced changes in the fluvial regime with more efficient sediment transport during insolation maxima this orbital control also modulated the long term pattern of the wmdw intensity as illustrated by the silt clay ratio however deep convection was particularly sensitive to climatic changes at shorter time scales i e to centennial millennial glacial and holocene oscillations that are well documented by all the paleocurrent intensity proxies si al ti al and silt clay ratios benthic isotopic records 13c and 18o show a dansgaard oeschger d o pattern of variability of wmdw properties which can be associated with changing intensities of the deep currents system the most prominent reduction on the wmdw overturning was caused by the post glacial sea level rise three main scenarios of wmdw overturning are revealed a strong mode during d o stadials a weak mode during d o interstadials and an intermediate mode during cooling transitions in addition d o stadials associated with heinrich events hes have a very distinct signature as the strong mode of circulation typical for the other d o stadials was never reached during he due to the surface freshening induced by the inflowing polar waters consequently the wmdw overturning system oscillated around the intermediate mode of circulation during he though surface conditions were more stable during the holocene the wmdw overturning cell still reacted synchronously to short lived events as shown by increments in the planktonic 18o record triggering quick reinforcements of the deep water circulation overall these results highlight the sensitivity of the wmdw to rapid climate change which in the recent past were likely induced by oceanographic and atmospheric reorganizations in the north atlantic region

a biomarker approach to the organic matter deposited in the north atlantic during the last climatic cycle abstract the study of the composition of total organic carbon toc c37 alkenones and c23 c33 n alkanes in the north atlantic ocean cores su90 08 and su90 39 has allowed the development of a model for the differentiation of marine and terrigenous toc this model gives rise to results in good agreement with inorganic markers such as magnetic susceptibility ms and non carbonate content according to this model the terrigenous toc accounts for most of the organic matter in the glacial sediments thus the higher toc of the glacial periods 0 1 0 45 vs 0 05 0 15 in the interglacials is due to the increase in terrigenous toc the changes in marine toc those associated to sea surface productivity are independent of the glacial interglacial evolution the terrigenous toc is more important at higher latitudes probably due to higher terrigenous detrital inputs associated with iceberg transport in this respect the correlation between n alkanes and ms strongly suggests that the main source of these hydrocarbons are ice rafted materials and that aeolian inputs only represent minor contributions the four peaks of reworked n alkanes in the su90 08 core that are coincident with the heinrich layers h1 h2 h4 and 115 are in agreement with this hypothesis on the other hand the abrupt marine toc peaks of su90 08 show a 23 ka periodicity indicating that the marine productivity at 43 n in the north atlantic ocean was precessionally driven the productivity maxima in this core correlate with low latitude oceanographic processes such as periods of enhanced trade wind intensity and equatorial upwelling which are also tuned to precession and independent of the global glacial interglacial evolution

low frequency cultural noise 1 abnormal cultural seismic noise is observed in the frequency range of 0 01 0 05 hz cultural noise generated by human activities is generally observed in frequencies above 1 hz and is greater in the daytime than at night the low frequency noise presented in this paper exhibits a characteristic amplitude variation and can be easily identified from time domain seismograms in the frequency range of interest the amplitude variation is predominantly in the vertical component but the horizontal components also show variations low frequency noise is markedly periodic which reinforces its interpretation as cultural noise such noise is observed world wide but is limited to areas in the vicinity of railways the amplitude variation in seismograms correlates strongly with railway timetables and the waveform shows a wavelength shift associated with the doppler effect which indicates that the origin of seismic background noise in the frequency range 0 01 0 05 hz is railways

single force representation of earthquakes due to landslides or the collapse of caverns summary earthquakes due to landslides and the collapse of caverns are caused by the release of gravitational potential energy rather than elastic strain energy landslide or cavern collapse is assumed to start with dislocation motion along the lubricated interface of the slide block or fallen block that intersects the earth s free surface it can be shown that if each component of the dislocation vector is positionindependent and varies only as a function of time the resultant static displacement is spatially uniform both inside and outside the block and therefore no change occurs in static strain energy in particular if the medium is unbounded the static displacement is zero outside the block the force system equivalent to this dislocation model is a distribution of single forces equal but opposite to the dislocation acceleration multiplied by the density at each point of the volume constituting the slide block the physics behind the equivalence is discussed single force appears to be a common mechanism for indigeneous earthquakes that do not change the static strain field

paleoenvironmental change in a precession paced succession across the onset of the messinian salinity crisis insight from element geochemistry and molecular fossils abstract in marginal mediterranean sub basins the early phase of the messinian salinity crisis msc is recorded by cyclic successions of gypsum and shales which in deeper parts of the sub basins make lateral transition into organic rich shales marls and carbonates the cyclic stacking pattern of the gypsum bearing sequences is assumed to reflect periodic paleoenvironmental change induced by precession driven climate perturbations with the assumption that shales reflect humid climate precession minima while gypsum reflects arid conditions precession maxima however this correlation has not been verified to date mostly because of the scarcity of microfossils the most commonly used tools for the reconstruction of precession driven paleoenvironmental change such change can instead be reconstructed through the study of the deeper water counterparts of gypsum marly and carbonate layers with geochemical indicators major and trace elements molecular fossils which provide insight on climate and aquatic productivity we used this approach to study a section from the piedmont basin nw italy where the onset of the msc is archived in a sequence of organic rich sediments this sequence displays distinct lithological cyclicity evidenced by the repetition of couplets of organic rich shales and marls either bioturbated in the pre msc part of the section or laminated during the msc the influence of orbitally driven precession climate oscillations is demonstrated by fluctuations of ti al si al mg al k al zr al and ba al ratios that are in phase with lithological cyclicity these fluctuations are interpreted to reflect alternation of humid shales deposited during precession minima and arid bioturbated and laminated marls deposited during precession maxima phases dominated by fluvial and aeolian transport of detrital material respectively the cyclicity of the element ratios is mirrored by changes in organic carbon content and molecular fossil inventory in particular the distribution of long chain n alkanes and their degree of preservation reveal that humid phases at times of precession minima were typified by the maximum input of degraded terrestrial organic matter driven by enhanced riverine runoff which promoted water column stratification coeval increase in ba content a common paleoproductivity proxy agrees with enhanced nutrient supply during humid periods promoting phases of eutrophication in the basin lithological and geochemical changes are observed in msc sediments deposited at times of precession maxima evidenced by the replacement of pre msc bioturbated marls by laminated marls rich in filamentous fossils corresponding to the remains of probable colorless sulfide oxidizing bacteria such changes reflect an intensification of water column stratification after the onset of the msc possibly related to the combined effect of persistent freshwater inflow and basin isolation preluding the advent of gypsum precipitation

enhanced aridity and atmospheric high pressure stability over the western mediterranean during the north atlantic cold events of the past 50 k y multiproxy paleoenvironmental records pollen and planktonic isotope from ocean drilling program site 976 alboran sea document rapid ocean and climate variations during the last glacial that follow the dansgaard oeschger climate oscillations seen in the greenland ice core records thus suggesting a close link of the mediterranean climate swings with north atlantic climates continental conditions rapidly oscillated through cold arid and warm wet conditions in the course of stadial interstadial climate jumps at the time of heinrich events i e maximum meltwater flux to the north atlantic western mediterranean marine microflora and microfauna show rapid cooling correlated with increasing continental dryness enhanced aridity conceivably points to prolonged wintertime stability of atmospheric high pressure systems over the southwestern mediterranean in conjunction with cooling of the north atlantic

impact of iceberg melting on mediterranean thermohaline circulation during heinrich events down core samples of planktonic and benthic foraminifera were analyzed for oxygen and carbon isotopes in international marine past global changes study images core md99 2343 in order to study the interactions between climate change in the northern hemisphere and the western mediterranean thermohaline circulation at times of heinrich events he our results confirm the antiphase correlation between enhanced north atlantic deep water formation and low ventilation in the mediterranean however this study reveals that this antiphase relationship in deepwater formation between the north atlantic and mediterranean was interrupted during times of he when the injection of large volumes of water from melting icebergs reached the entrance to the mediterranean these events which lasted less than 1000 years are represented by pronounced decreases in both planktonic d18o and benthic d13c signals lower salinities of mediterranean surface water resulted in a slowdown of western mediterranean deepwater overturn even though cold sea surface temperatures and drier climate should have resulted in enhanced deepwater formation

molecular proxies for paleoclimatology we summarize the applications of molecular proxies in paleoclimatology marine molecular records especially are proving to be of value but certain environmentally persistent compounds can also be measured in lake sediments loess deposits and ice cores the fundamentals of this approach are the molecular parameters the compound abundances and carbon hydrogen nitrogen and oxygen isotopic contents which can be derived by the analysis of sediment extracts these afford proxy measures which can be interpreted in terms of the conditions which control climate and also reflect its operation we discuss two types of proxy those of terrigenous and those of aquatic origin and exemplify their application in the study of marine sediments through the medium of ten case studies based in the atlantic mediterranean and pacific oceans and in antarctica the studies are mainly for periods in the present the holocene and particularly the last glacial interglacial but they also include one study from the cretaceous the terrigenous proxies which are measures of continental vegetation are based on higher plant leaf wax compounds i e long chain circa c30 hydrocarbons alcohols and acids they register the relative contributions of c3 vs c4 type plants to the vegetation in the source areas the two marine proxies are measures of sea surface temperatures sst the longer established one u37k is based on the relative abundances of c37 alkenones photosynthesized by unicellular algae members of the haptophyta the newest proxy tex86 is based on c86 glycerol tetraethers gdgts synthesized in the water column by some of the archaeal microbiota the crenarchaeota

similarities and dissimilarities between the last two deglaciations and interglaciations in the north atlantic region abstract sea surface temperatures ssts recorded by alkenones and oxygen isotopes in the alboran basin are used here to describe at an unprecedented fine temporal resolution the present interglaciation pig initiated at 11 7 ka bp the last interglaciation lig onset approximately at 129 ka and respective deglaciations similarities and dissimilarities in the progression of these periods are reviewed in comparison with ice cores and stalagmites cold spells coeval with the heinrich events h described in the north atlantic include multi decadal scale oscillations not previously obvious up to 4 c in less than eight centuries within the stadials associated with h1 and h11 ca 133 ka and 17 ka respectively these abrupt oscillations precede the accumulation of organic rich layers deposited when perihelion moves from alignment with nh spring equinox to the summer solstice a reference for deglaciations events observed during the last deglaciation at 17 ka 14 8 ka and 11 7 ka are reminiscent of events occurred during the penultimate deglaciation at ca 136 ka 132 ka and 129 ka respectively the sst trend during the pig is no more than 2 c from 20 c to 18 c up to 0 2 c ka the trend is steeper during the lig i e up to a 5 c change from the early interglaciation to immediately before the glacial inception from 23 c to 18 c up to 0 4 c ka events are superimposed upon a long term trend towards colder ssts beginning with sst maxima followed by temperate periods until perihelion aligned with the nh autumn equinox before ca 5 3 ka for the pig and 121 ka for the lig a cold spell of around eight centuries at 2 8 ka during the pig was possibly mimicked during the lig at ca 118 ka by a sst fall of around 1 c in a millennium these events led interglacial sst to stabilise at around 18 c the glacial inception barely evident at the beginning ca 115 ka north atlantic event c25 after perihelion passage in the nh winter solstice culminated with a sst drop of at least 2 c in two millennia event c24 ca 111 ka the little ice age 0 7 ka also occurred after the latest perihelion passage in the nh winter solstice and could be an example of how a glacial pre inception event following an interglaciation might be

millennial scale oceanic climate variability off the western iberian margin during the last two glacial periods high resolution palaeoclimate records recovered from the iberian margin in core md95 2040 exhibit large fluctuations in oceanographic conditions over the last 190 ka large scale cooling of the surface ocean is indicated by the presence of the polar planktonic foraminifer neogloboquadrina pachyderma sinistral and in some instances the occurrence of ice rafted debris ird ice rafting episodes were prevalent in both of the last two glacials with greater intensity in stages 2 through 4 than in stage 6 the six youngest heinrich events are well defined during the last glacial but detrital carbonate is absent from heinrich layers hl6 hl5 and hl3 dansgaard oeschger stadial equivalent sub millennial ird deposition events have been detected in particular during stage 3 allowing a good match with the cooling displayed in the greenland ice core gisp2 sea surface temperature off portugal in stage 6 was in general warmer than during the last glacial pointing towards a weaker southward influence of polar water masses ice rafting occurred mainly in mid mis marine isotope stage 6 between 173 and 153 kyr as a group of poorly differentiated short duration quasi continuous events mainly marked by the high abundance of sinistral n pachyderma differences exist in ird composition relative to the last glacial with a reduced canadian derived detrital carbonate component combined with an important contribution of volcanic particles the lower magnitude and higher frequency of these events suggest that the higher temperatures would have induced iceberg waning closer to the source areas

timing of millennial scale climate change in antarctica and greenland during the last glacial period a precise relative chronology for greenland and west antarctic paleotemperature is extended to 90 000 years ago based on correlation of atmospheric methane records from the greenland ice sheet project 2 and byrd ice cores over this period the onset of seven major millennial scale warmings in antarctica preceded the onset of greenland warmings by 1500 to 3000 years in general antarctic temperatures increased gradually while greenland temperatures were decreasing or constant and the termination of antarctic warming was apparently coincident with the onset of rapid warming in greenland this pattern provides further evidence for the operation of a bipolar see saw in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales

phase relationship between sea level and abrupt climate change direct traces of past sea levels are based on the elevation of old coral reefs at times of sea level high stands however these measurements are discontinuous and cannot be easily correlated with climate records from ice cores in this study we show a new approach to recognizing the imprint of sea level changes in continuous sediment records taken from the continental slope at locations that were continuously submerged even during periods of sea level lowstand by using a sediment core precisely synchronized with greenland ice cores we were able to recognize major floods of the mediterranean continental shelf over the past 270 kyr during the last glacial period five flooding events were observed at the onset of the warmest greenland interstadials consistent correspondence between warm climate episodes and eustatic sea level rises shows that these global flooding events were generated by pronounced melting of the northern hemisphere ice sheets due to rapid intensification of atlantic meridional overturning circulation the method described in this study opens a new perspective for inter hemi spheric synchronization of marine climate records if applied in other continental margins from the southern hemisphere or the equatorial regions c 2009 elsevier ltd all rights reserved

links between marine and atmospheric processes oscillating on a millennial time scale a multi proxy study of the last 50 000 yr from the alboran sea western mediterranean sea abstract the large dataset obtained from the extensive study of images core md95 2043 recovered from the alboran sea western mediterranean shows the periodicities and phase relationships of oceanographic and atmospheric processes on a millennial time scale the 1470 yr cycle is the most significant with the exception of the records reflecting climatic or environmental changes on land which show statistically significant 3300 and 8000 frequency bands the investigation of these core records on a millennial scale resolution allows us to establish the evolution of oceanographic and atmospheric mechanisms that influenced the western mediterranean region in the course of the dansgaard oeschger cycles accordingly possible land sea interactions can be identified and situated in the context of the temporal succession of the different climatic processes for instance saharan dust supply from northern africa appears to lead high latitude climate changes suggesting that low latitude feedback processes were involved in forcing the millennial climatic variability in the westernmost mediterranean

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

the impact of ice sheet dynamics in western mediterranean environmental conditions during terminations an approach based on terrestrial long chain n alkanes deposited in the upper slope of the gulf of lions abstract during the promess campaign summer 2004 a borehole prgl1 was drilled in the upper slope of the gulf of lions previous studies showed that the deposition of the sedimentary units at borehole prgl1 was determined by changes in the discharge of the rhone river induced by sea level and climate variability with a strong 100 ka imprint however there are no detailed studies that focus on the glacial interglacial transitions i e terminations that define 100 ka quaternary ice age cycles here we present a high resolution record of terrestrial long chain n alkanes c21 to c33 from mis 3 to mis 11 in order to monitor changes in the sediments deposited on the upper slope of the gulf of lions with the aim to provide new insight into the climatic events occurring during terminations in the western mediterranean sea principal component analysis grouped n alkane on the basis of the degree of maturation of organic matter fresh degraded that allowed to monitor past variability in the source of the sediment deposited in the upper slope as a consequence of sea level and climate change this information was used to estimate the impact that northern ice sheet variability had on the western mediterranean basin as sea level started to fall fresh terrestrial organic matter increased owing to the seaward migration of rhone s mouth simultaneously the decrease in sea level exposed old and reworked organic material from the rhone s catchment including the delta plain and the continental shelf that was eroded and transported into our study site this resulted in an increase in the proportion of degraded terrestrial organic matter together with sea level decrease aside from sea level changes the proportion of fresh vs degraded organic matter seems to be affected by the amount of continental runoff with an increasing proportion of fresh terrestrial organic matter occurring at times of reduced continental runoff during the last glacial the increase of fresh terrestrial organic matter was contemporaneous with heinrich events hes suggesting dry and cold conditions on the western mediterranean basin these dry and cold millennial scale episodes were reproduced during terminations ii iii and iv preceding flood events most probably due to weakening reinforcement of atlantic meridional overturning circulation amoc that caused dry humid conditions in western mediterranean

ambient noise rayleigh wave tomography of new zealand summary we present the first new zealand wide study of surface wave dispersion using ambient noise observed at 42 broad band stations in the national seismic network geonet and the global seismic network gsn year long vertical component time series recorded between 2005 april 1 and 2006 march 31 have been correlated with one another to yield estimated fundamental mode rayleigh wave green s functions we filter these green s functions to compute rayleigh wave group dispersion curves at periods of 5 50 s using a phase matched filter frequency time analysis technique the uncertainties of the measurements are estimated based on the temporal variation of the dispersion curves revealed by 12 overlapping 3 month stacks after selecting the highest quality dispersion curve measurements we compute group velocity maps from 7 to 25 s period these maps and 1 d shear wave velocity models at four selected locations exhibit clear correlations with major geological structures including the taranaki and canterbury basins the hikurangi accretionary prism and previously reported basement terrane boundaries

simulations of long period ground motions from a large earthquake using finite rupture modeling and the ambient seismic field long period ground motions generated by large earthquakes slowly attenuate with distance and can be significantly amplified by local velocity structures even at large distances we take advantage of the wave propagation information carried by the ambient seismic field to simulate the long period ground motions of the 2008 mw 6 9 iwate miyagi nairiku earthquake which occurred in the tohoku region japan we extract green s functions between pairs of stations by regarding seismometers located in the vicinity of the mainshock fault plane as virtual sources and others as receivers we calibrate the amplitude of the extracted green s functions using records of a mw 5 0 aftershock with a reverse faulting focal mechanism similar to that of the mainshock we use scaling relations between small and large earthquakes to construct several finite fault models that are used together with the extracted green s functions to simulate the ground motions of the mainshock among the different models a uniform finite source model with a rupture velocity of 1 95 km s combined with the green s functions extracted using one virtual source station located at the center of the fault plane yields the best fit between the simulated and observed long period ground motions this study demonstrates the potential of the ambient seismic field combined with finite source modeling to assess the seismic hazard related to long period ground motions that could be generated by forthcoming large earthquakes