mg ca temperature calibration for costate bulimina species b costata b inflata b mexicana a paleothermometer for hypoxic environments abstract costate species of bulimina are cosmopolitan infaunal benthic foraminifers which are common in the fossil record since the paleogene in the present study we evaluate the temperature dependency of mg ca ratios in bulimina inflata b mexicana and b costata from an extensive set of core top samples from the atlantic pacific and indian oceans the results show no significant offset in mg ca values between costate morphospecies when present in the same sample the apparent lack of significant inter specific inter morphotype differences amongst the analyzed costate buliminids allows for the combined use of their data sets for our core top calibration over a bottom water temperature bwt range of 3 13 c the bulimina species show a sensitivity of 0 12 mmol mol c which is comparable to that of epifaunal cibicidoides species and higher than that of the shallow infaunal uvigerina spp the most commonly used taxon in mg ca based palaeotemperature reconstruction the reliability and accuracy of the new mg ca temperature calibration is corroborated in the fossil record by a case study in the timor sea which demonstrates the presence of southern sourced waters at intermediate depths for the past 26 000 years costate species of bulimina might thus provide a valuable alternative for bwt reconstruction in mesotrophic to eutrophic settings where many of the commonly used more oligotrophic species are rare or absent and be particularly useful in hypoxic settings such as permanent upwelling zones where costate buliminids often dominate foraminiferal assemblages the evaluation further reveals a mean positive offset of 0 2 mmol mol of the atlantic data set over the indo pacific data set which contributes to the scatter in our calibration although an explanation for this offset is not straightforward and further research is necessary we hypothesize that different levels of export production and carbonate ion concentrations in pore waters are likely reasons

early human occupation of a maritime desert barrow island north west australia abstract archaeological deposits from boodie cave on barrow island northwest australia reveal some of the oldest evidence for aboriginal occupation of australia as well as illustrating the early use of marine resources by modern peoples outside of africa barrow island is a large 202 km 2 limestone continental island located on the north west shelf of australia optimally located to sample past use of both the pleistocene coastline and extensive arid coastal plains an interdisciplinary team forming the barrow island archaeology project biap has addressed questions focusing on the antiquity of occupation of coastal deserts by hunter gatherers the use and distribution of marine resources from the coast to the interior and the productivity of the marine zone with changing sea levels boodie cave is the largest of 20 stratified deposits identified on barrow island with 20 m 3 of cultural deposits excavated between 2013 and 2015 in this first major synthesis we focus on the dating and sedimentology of boodie cave to establish the framework for ongoing analysis of cultural materials we present new data on these cultural assemblages including charcoal faunal remains and lithics integrated with micromorphology sedimentary history and dating by four independent laboratories first occupation occurs between 51 1 and 46 2 ka overlapping with the earliest dates for occupation of australia marine resources are incorporated into dietary assemblages by 42 5 ka and continue to be transported to the cave through all periods of occupation despite fluctuating sea levels and dramatic extensions of the coastal plain the changing quantities of marine fauna through time reflect the varying distance of the cave from the contemporaneous shoreline the dietary breadth of both arid zone terrestrial fauna and marine species increases after the last glacial maximum and significantly so by the mid holocene the cave is abandoned by 6 8 ka when the island becomes increasingly distant from the mainland coast

the last reconnection of the marmara sea turkey to the world ocean a paleoceanographic and paleoclimatic perspective during the late glacial marine isotope stage 2 the marmara sea transformed into a brackish lake as global sea level fell below the sill in the dardanelles strait a record of the basin s reconnection to the global ocean is preserved in its sediments permitting the extraction of the paleoceanographic and paleoclimatic history of the region the goal of this study is to develop a high resolution record of the lacustrine to marine transition of marmara sea in order to reconstruct regional and global climatic events at a millennial scale for this purpose we mapped the paleoshorelines of marmara sea along the northern eastern and southern shelves at cekmece prince islands and imrali using data from multibeam bathymetry high resolution subbottom profiling chirp and ten sediment cores detailed sedimentologic biostratigraphic foraminifers mollusk diatoms x ray fluorescence geochemical scanning and oxygen and carbon stable isotope analyses correlated to a calibrated radiocarbon chronology provided evidence for cold and dry conditions prior to 15 ka bp warm conditions of the bolling allerod from 15 to 13 ka bp a rapid marine incursion at 12 ka bp still stand of marmara sea and sediment reworking of the paleoshorelines during the younger dryas at 11 5 to 10 5 ka bp and development of strong stratification and influx of nutrients as black sea waters spilled into marmara sea at 9 2 ka bp stable environmental conditions developed in marmara sea after 6 0 ka bp as sea level reached its present shoreline and the basin floors filled with sediments achieving their present configuration

spatial distribution of live benthic foraminifera in the rhone prodelta faunal response to a continental marine organic matter gradient abstract benthic foraminifera were collected in the rhone prodelta gulf of lions mediterranean sea an enriched zone with high organic matter content in june 2005 sediment cores were sampled at depths ranging from 20 to 100 m four distinct foraminiferal assemblages were determined in the study area reflecting the geographical distribution of the impact of river supply the living foraminiferal faunas present a typical picture with strongly impoverished faunas composed exclusively of stress tolerant taxa fursenkoina fusiformis bulimina aculeata leptohyalis scottii and adelosina longirostra in the immediate vicinity of the river mouth this assemblage is well adapted to a high input of continental organic matter and a minimum oxygen penetration depth into the sediment to the southwest under the main corridor followed by the river plume high organic input with a dominantly terrestrial signature more refractory may be stressful for many taxa which need organic matter of a more labile quality in this area nonion scaphum nonionella turgida and rectuvigerina phlegeri are present in low densities on the edge of this area these taxa show much higher densities a greater proportion of marine organic carbon could explain their increasing abundances in this area towards the east and towards the deepest stations in the outer part of the enriched zone biodiversity increases faunas at these stations have intermediate densities and contain a number of taxa cassidulina carinata epistominella vitrea valvulineria bradyana nonionella iridea bradyi at the deepest stations bolivina dilatata spathulata and textularia porrecta at the eastern stations that seem to benefit from more marine organic matter the comparison of geochemical measurements and foraminiferal data strongly suggests that the spatial distribution of foraminifera in the rhone prodelta is mainly governed by the quality and the quantity of organic matter reaching the sediment water interface since bottom waters are well oxygenated 215 260 mol l and oxygen penetration into the sediment is less than 1 cm at all stations benthic ecosystem oxygenation appears to have only a minor impact on regional differences in faunal distribution

large variations in travel times of mantle sensitive seismic waves from the south sandwich islands is the earth s inner core a conglomerate of anisotropic domains 1 cylindrical anisotropy in earth s inner core has been invoked to account for travel times of pkp core sensitive seismic waves such as from the south sandwich islands ssi earthquakes observed in alaska which depart from predictions newly collected travel time residuals from seismic waves from the ssi region that sample only earth s mantle pcp and p waves have a comparable range to the pkp differential travel time residuals yet they are insensitive to core structure this observation suggests that mantle structure affects pkp travel time residuals more than previously acknowledged and challenges the existing conceptual framework of a uniform inner core anisotropy the inner core could be a conglomerate of anisotropic domains and the pkp travel times are most likely influenced by the geometry of inner core sampling and inhomogeneous mantle structure this concept reconciles observed complexities in travel times while preserving a net inner core anisotropy that is required by observations of earth s free oscillations

benthic foraminiferal response to changes in bottom water oxygenation and organic carbon flux in the eastern mediterranean during lgm to recent times abstract we present a high resolution study of benthic foraminiferal abundances in 4 cores from the central aegean and ne levantine seas spanning the interval from 30 ka bp to the present the benthic foraminiferal faunas indicate that during lgm times bottom waters were well ventilated while organic flux to the sea floor was significantly higher than today from 30 to 10 2 ka bp faunal density and composition suggest a gradual decrease in organic flux to the sea floor this trend is interrupted by a short return to higher organic flux levels during the younger dryas 12 8 11 5 ka bp the faunas immediately preceding the early to middle holocene organic rich layer sapropel s1 are very similar to late holocene faunas indicating oligotrophic conditions the transition from well ventilated bottom waters to anoxic levantine basin or strongly dysoxic aegean sea bottom waters appears to take place within a time span of only 600 years from 10 8 to 10 2 ka bp sapropel s1 10 2 6 4 ka bp is characterized by extended periods of bottom water anoxia in the levantine basin and by strongly dysoxic conditions punctuated by episodic re ventilation events in the aegean sea re establishment of fully oxygenated bottom water conditions after sapropel s1 was extremely rapid the ensuing late holocene faunas are very similar to recent faunas found in the aegean sea suggesting much lower fluxes of organic matter to the sea floor than during glacial times

relationships between anoxia glacial meltwater and microfossil preservation in the orca basin gulf of mexico abstract the isotopic and microfossil records from piston core en32 pc6 from the orca basin gulf of mexico reveal that various factors have moderated the sediment composition of the basin during the last 29 000 yrs 29 ka b p coincident with the introduction of isotopically depleted glacial meltwater into the gulf approximately 16 ka b p anoxic conditions commenced within the intraslope basin as evidenced by sedimentary laminations and improved microfossil pteropod planktonic foraminifera and radiolaria preservation the increased delivery of terrigenous organic matter with the glacial meltwater may have been responsible for inducing the anoxia also at this time the water of the orca basin was most likely somewhat stratified due to elevated salinities and the increased supply of organic matter onto the continental slope from the continent would have depleted the oxygen supply of the orca basin by oxidative consumption about 13 ka b p oxygenated conditions resumed and microfossil abundance preservation decreased when meltwater input diminished at 8 5 ka b p the orca basin again became anoxic due to the development of the orca basin brine

evidence for a chemical thermal structure at base of mantle from sharp lateral p wave variations beneath central america compressional waves that sample the lowermost mantle west of central america show a rapid change in travel times of up to 4 s over a sampling distance of 300 km and a change in waveforms the differential travel times of the pkp waves which traverse earth s core correlate remarkably well with predictions for s wave tomography our modeling suggests a sharp transition in the lowermost mantle from a broad slow region to a broad fast region with a narrow zone of slowest anomaly next to the boundary beneath the cocos plate and the caribbean plate the structure may be the result of ponding of ancient subducted farallon slabs situated near the edge of a thermal and chemical upwelling

large scale structure at the core mantle boundary from diffracted waves at the base of the earth s mantle is a region called d which serves as a thermal and chemical boundary layer between the silicate mantle and the liquid iron outer core1 2 tomographic models of mantle compressional wave velocity vp have their worst resolution in d owing to limited ray sampling3 5 but have hinted at large scale lateral variations there here i use a new technique which has its greatest resolution within d to produce a map of the large scale vp variations within d the technique compares the arrival times of waves that have been refracted across and diffracted around the core mantle boundary cmb the diffracted waves travel a long way in d making them excellent probes of this layer and the differential technique removes many effects arising from ray paths outside of d ref 6 the new map provides an image of the continent sized variations at the cmb that is complementary to existing shear wave data7 8 and similarities between the map and projections of ancient subducted lithosphere9 verify previous suggestions10 of a strong coupling between surface plate tectonics and the base of the mantle

upper mantle slab under alaska contribution to anomalous core phase observations on south sandwich to alaska paths abstract observations of travel time anomalies of inner core sensitive pkpdf seismic body waves as a function of path orientation with respect to the earth s rotation axis have been interpreted as evidence of anisotropy in the inner core paths from earthquakes in the south sandwich islands to stations in alaska show strongly anomalous travel times with a large spread that is not compatible with simple models of anisotropy here we assess the impact of strong velocity heterogeneity under alaska on the travel times directions of arrival and amplitudes of pkpdf we use 3d ray tracing and 2 5d waveform modelling through a new high resolution tomography model of the upper mantle beneath alaska we find that the structure beneath alaska notably the subducting slab is reflected in the patterns of these pkpdf observations and this can be replicated by our model we also find similar patterns in observed teleseismic p waves that can likewise be explained by our slab model we conclude that at least 2 s of the travel time anomaly often attributed to inner core anisotropy is due to slab effects in the upper mantle beneath alaska

seismic velocity and attenuation structures in the top of the earth s inner core 1 we collect a global data set of pkikp and pkikp phases recorded by the global seismic network and many regional seismic arrays to study seismic structure in the top of the earth s inner core the pkikp and pkikp observations show different characteristics between those sampling the eastern hemisphere 40 e 180 e of the inner core and those sampling the western hemisphere 180 w 40 e pkikp phases 1 arrive about 0 4 s earlier than the theoretical arrivals based on preliminary reference earth model prem for those sampling the eastern hemisphere of the inner core and about 0 3 s later for those sampling the western hemisphere 131 141 2 bifurcate at smaller epicentral distances for those sampling the eastern hemisphere compared to those sampling the western hemisphere and 3 have smaller amplitudes for those sampling the eastern hemisphere waveform modeling of these observations suggests two different types of models for the two hemispheres of the top of the inner core with a model in the eastern hemisphere having a p velocity increase of 0 765 km s across the inner core boundary a small radial velocity gradient of 0 000055 km s km and an average q value of 250 and a model in the western hemisphere with a p velocity increase of 0 633 km s across the inner core boundary a radial velocity gradient of 0 000533 km s km and an average q value of 600 the hemispherical difference of seismic structures may be explained by different geometric inclusions of melt and or different alignments of iron crystals with anisotropic properties in both velocity and attenuation we speculate that this large scale pattern of seismic heterogeneities may be caused by a large scale heat flow anomaly at the bottom of the outer core and or different vigorousness of convection in the top of the inner core between the two hemispheres

radiocarbon dating of charcoal from tropical sequences results from the niah great cave sarawak and their broader implications subsamples of charcoal from a number of different excavation contexts at the early modern human homo sapiens site of niah great cave malaysia were accelerator mass spectrometry ams 14c dated samples were prepared using one of a number of different methods untreated control acid base acid aba and acid base wet oxidation with stepped combustion abox sc after bird et al 1999 the results show that for material younger than 25 ka bp there is little difference between the two chemical pretreatment methods and the control for charcoal beyond 25 ka bp however there are differences of up to 4000 a with abox sc ages being consistently older this is argued to be a more effective pretreatment method for decontaminating charcoal samples prior to radiocarbon dating for radiocarbon dating charcoals greater than 25 ka bp the abox sc pretreatment and combustion approach appears to be the most rigorous method for developing a robust chronological framework for tropical sequences and should be more widely applied in contexts where the material being dated is likely to be ancient the new chronology developed for niah cave based on this technique suggests that the earliest human evidence dates back to at least 45 ka bp and may extend significantly earlier than this based on the recent discovery of lithics 50 cm below the earliest dated charcoal copyright 2008 john wiley sons ltd

joint inversion of normal mode and body wave data for inner core anisotropy 1 laterally homogeneous anisotropy 1 we use mantle and inner core sensitive normal modes to invert for laterally varying mantle models and a transversely isotropic inner core to obtain an inner core model that is compatible with long period mode and short period body wave data we incorporate mantle corrected absolute travel time and differential travel time data in our inversions using this diverse data set we investigate the dependence of inner core models upon mantle parameterization and possible radial structure within the inner core inner core anisotropy obtained from a simultaneous inversion for mantle and inner core structure has a weak dependence upon the parameterization within the mantle that is the results for the inner core are insensitive to whether the mantle is inverted only for shear velocity structure or for shear and compressional velocity structure as well as density an inner core model with constant anisotropy is capable of fitting all types of data but mode and absolute travel time data are more compatible with one another than with differential travel time data allowing for radial variations within the inner core reduces this incompatibility and it is possible to obtain a radially dependent model that fits normal mode absolute travel time and differential travel time data with a variance reduction greater than 75

environmental control on shell structure and composition of agglutinated foraminifera along a proximal distal transect in the marmara sea abstract the study of benthic foraminifera in a complex marine system like the marmara sea is a key for understanding the influence of environmental factors on foraminiferal species density assemblage composition and shell construction this kind of study is important for further extensive use of foraminifera based investigation of water mass and sediment exchange between the eastern mediterranean and black sea through the marmara sea based on proximal distal transect from the southwest coast of the erdek bay to the top of canyon close to the north anatolian fault this study aims at defining the geochemical conditions at the seafloor and identifying the sediment constraints that act upon agglutinated test construction for selected species eggerelloides scaber textularia agglutinans textularia sagittula textularia truncata and textularia bocki grain size mineralogical and chemical analyses of their shells were investigated and confronted with the main geochemical conditions prevailing during deposition and within the sediment among grains used to construct the agglutinated foraminiferal tests from available grains both grain size selection and sorting have been evidenced this suggests that the mineralogical composition is related to the species and the sample localization within the basin our observations further suggest that bottom water conditions of the marmara sea do not have a significant influence on agglutinated foraminiferal shell development which is primarily driven by sediment characteristics our results are thus transposable to other environments

recent benthic foraminifera from the continental margin of northwest africa community structure and distribution abstract sediment grab samples were collected at 107 locations along the continental margin of northwest africa these samples form a series of depth transects between the straits of gibraltar and dakar senegal the greater than 250 m size fraction was retained for a census of both the live and dead foraminifera after deleting trace occurrences jaccard and correlation coefficient based cluster analyses were performed to decipher the community structure for this margin the geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth upper slope and shelf middle slope and lower slope and continental rise the biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using jaccard coefficients dendrograms constructed from correlation coefficients emphasize depth related faunal communities dominant species such as cibicides lobatulus trifarina fornasinii planulina ariminensis uvigerina finisterrensis and c wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient based dendrograms other distributions are clearly not depth related but correspond to various environmental variables for example cancris auriculus coarse substrate bolivina subaenariensis oxygen minimum cibicidoides kullenbergi and hoeglundina elegans low organic carbon uvigerina peregrina is also a notable exception to depth dependence in that this dominant species and the province it represents are generally confined to the continental slope south of cape blanc its preference for that region may arise from the high organic carbon and fine grain size of the sediment there from low salinity of the bottom water or from other unknown variables the most important vertical faunal boundary occurs between cape barbas and cape blanc between 22 and 21 n latitude in contrast the canary island ridge intersects the continental margin at a saddle depth of about 1500 m but that physiographic barrier has little effect on provincialism of the deep water benthic foraminifera

seismic anisotropy of the earth s inner core resulting from flow induced by maxwell stresses seismological observations indicate that the inner core of the earth is elastically anisotropic1 anisotropic structures are likely to be formed by dynamic processes and therefore such observations have the potential to provide constraints on flow in the inner core and on the geodynamo itself but in addition to the difficulties in estimating the relevant physical properties of iron under inner core conditions2 3 4 even the macroscopic processes responsible for generating seismic anisotropy in this region have yet to be determined5 6 7 8 9 as a result the geodynamic significance of seismic anisotropy in the inner core has remained unknown here i propose based on geodynamic and mineral physics considerations that flow induced by the stress due to the magnetic field the maxwell stress near the inner core boundary produces an axisymmetric fabric responsible for the observed seismic anisotropy the resultant seismic anisotropy reflects the geometry of the magnetic field near the inner core boundary and therefore seismological observations might provide constraints on the geodynamo this flow also causes non uniform release of energy at the inner core boundary associated with solidification and melting which may affect the pattern of convection in the outer core

three dimensional structure at the base of the mantle beneath the central pacific forward modeling of differential travel times of phases sensitive to lowermost mantle beneath the central pacific reveals lateral heterogeneity that is higher in amplitude than predicted by tomographic models a broad zone of low s velocity 4 percent with respect to standard models which may correspond to the base of a thermal plume narrows and is deflected as it extends to about 1000 kilometers above the core mantle boundary to the east of this zone a localized region of fast s velocity 5 percent suggests strong heterogeneity or anisotropy related to the presence of high pressure and temperature assemblages which may or may not involve core material its presence could also explain the observation of precursors to core reflected phases in this region

anisotropy in the deep earth abstract seismic anisotropy has been found in many regions of the earth s interior its presence in the earth s crust has been known since the 19th century and is due in part to the alignment of anisotropic crystals in rocks and in part to patterns in the distribution of fractures and pores in the upper mantle seismic anisotropy was discovered 50 years ago and can be attributed for the most part to the alignment of intrinsically anisotropic olivine crystals during large scale deformation associated with convection there is some indication for anisotropy in the transition zone particularly in the vicinity of subducted slabs here we focus on the deep earth the lower mantle and core where anisotropy is not yet mapped in detail nor is there consensus on its origin most of the lower mantle appears largely isotropic except in the last 200 300 km in the d region where evidence for seismic anisotropy has been accumulating since the late 1980s mostly from shear wave splitting measurements recently a picture has been emerging where strong anisotropy is associated with high shear velocities at the edges of the large low shear velocity provinces llsvps in the central pacific and under africa these observations are consistent with being due to the presence of highly anisotropic mgsio 3 post perovskite crystals aligned during the deformation of slabs impinging on the core mantle boundary and upwelling flow within the llsvps we also discuss mineral physics aspects such as ultrahigh pressure deformation experiments first principles calculations to obtain information about elastic properties and derivation of dislocation activity based on bonding characteristics polycrystal plasticity simulations can predict anisotropy but models are still highly idealized and neglect the complex microstructure of polyphase aggregates with strong and weak components a promising direction for future progress in understanding the origin of seismic anisotropy in the deep mantle and its relation to global mantle circulation is to link macroscopic information from seismology and microscopic information mineral physics through geodynamics modeling anisotropy in the inner core was proposed 30 years ago to explain faster p wave propagation along the direction of the earth s axis of rotation as well as anomalous splitting of core sensitive free oscillations there is still uncertainty about the origin of this anisotropy in particular it is difficult to explain its strength based on known elastic properties of iron as it would require almost perfect alignment of iron crystals indeed the strongly anomalous p travel times observed on paths from the south sandwich islands to alaska may or may not be due to inner core anisotropy and will need to be explained before consensus can be reached on the strength of anisotropy in the inner core and its origin

palaeoceanographic and palaeoclimatic changes during the last 37 000 years detected in the se bay of biscay based on benthic foraminifera abstract benthic foraminifera assemblages from a sedimentary core pp10 12 701 mwd from the se bay of biscay allow us to trace palaeoceanographic and palaeoclimatic changes occurred in this region during mid mis 3 marine isotope stage 3 and mis 1 interval 37 2 4 ka bp results are based on 176 benthic foraminifera species considering their ecology the difference between autochthonous allochthonous preservation and oxygen rates thus evidencing climatic and oceanographic events mis 3 is characterised by waters with a dominance of cassidulina laevigata and uvigerina peregrina by the end of this interval waters became colder and less oxygenated indicated by the occurrence of melonis affinis these conditions persisted at the beginning of mis 2 the heinrich event 1 h1 is well registered in this core with three intervals h1a h1s s h1b where hyalinea balthica dominates during h1s s the coldest waters are registered and the environment was unstable these conditions continued during h1b when the occurrence of globobulimina affinis evidences some intervals with anoxia during bolling allerod b a waters were warmer and low ventilated indicated by bulimina gibba cassidulina laevigata dominates the younger dryas yd and the beginning of lower holocene evidencing the occurrence of cool waters with low oxygen and high organic matter content the lower to middle holocene transition is registered as a cold interval holocene cooling event hce 5 from the middle holocene onward water temperature were milder based on the dominance of uvigerina peregrina

evidence for long lived subduction of an ancient tectonic plate beneath the southern indian ocean in this study ancient subducted tectonic plates have been observed in past seismic images of the mantle beneath north america and eurasia and it is likely that other ancient slab structures have remained largely hidden particularly in the seismic data limited regions beneath the vast oceans in the southern hemisphere here we present a new global tomographic image which shows a slab like structure beneath the southern indian ocean with coherency from the upper mantle to the core mantle boundary region a feature that has never been identified we postulate that the structure is an ancient tectonic plate that sank into the mantle along an extensive intraoceanic subduction zone that migrated southwestward across the ancient tethys ocean in the mesozoic era slab material still trapped in the transition zone is positioned near the edge of east gondwana at 140 ma suggesting that subduction terminated near the margin of the ancient continent prior to breakup and subsequent dispersal of its subcontinents

global p wave tomography of earth s lowermost mantle from partition modeling 1 determining the scale length magnitude and distribution of heterogeneity in the lowermost mantle is crucial to understanding whole mantle dynamics and yet it remains a much debated and ongoing challenge in geophysics common shortcomings of current seismically derived lowermost mantle models are incomplete raypath coverage arbitrary model parameterization inaccurate uncertainty estimates and an ad hoc definition of the misfit function in the optimization framework in response we present a new approach to global tomography apart from improving the existing raypath coverage using only high quality cross correlated waveforms the problem is addressed within a bayesian framework where explicit regularization of model parameters is not required we obtain high resolution images complete with uncertainty estimates of the lowermost mantle p wave velocity structure using a hand picked data set of pkpab df pkpbc df and pcp p differential travel times most importantly our results demonstrate that the root mean square of the p wave velocity variations in the lowermost mantle is approximately 0 87 which is 3 times larger than previous global scale estimates

constraints on d structure using pkp ab df pkp bc df and pcp p traveltime data from broad band records summary the effects of complex structure in the deep mantle and d on pkp differential traveltimes should be estimated accurately in order to reach reliable conclusions concerning the physical and chemical properties of the earth s inner and outer core in particular it is important to assess how much of the data can be explained by mantle structure alone for this purpose we have assembled global data sets of high quality pkp ab df pkp bc df and pcp p differential traveltimes measured on mostly broad band records the pkp ab df data were inverted alone or jointly with pcp p data to retrieve p velocity maps of the lowermost 300 km of the mantle corrections for mantle structure above d were performed prior to inversion using recent tomographic models and the fit to the pkp bc df data set was used to constrain damping in the inversions we compare models obtained with and without polar pkp paths and find that their inclusion or exclusion does not significantly affect the resulting d model except under north america where coverage is poor without polar paths our preferred model obtained using pkp ab df and pcp p data combined explains over 80 per cent of the variance in pkp ab df almost 60 per cent of the variance in pcp p and 27 per cent of the variance in pkp bc df a significant portion considering that the pkp bc df data set was not used in the inversion our models are characterized by prominent fast features under mid america and east asia a fast belt across the pacific a slow region under the southwestern pacific and southern africa as well as sharp transitions from fast to slow for instance under alaska and the south atlantic the anomalous south sandwich to alaska data cannot fully be explained by d structure alone unless very short wavelength lateral vari

differential burning recrystallization and fragmentation of archaeological bone abstract this paper presents research on the conditions under which progressive levels of burning may occur to archaeological bone and how burning damage changes bones crystal structure and susceptibility to fragmentation a k a friability experiments were conducted to simulate common patterns of high temperature bone diagenesis and fragmentation previously documented in paleolithic shelter sites bones buried up to 6 cm below the coal beds of the experimental fires were carbonized but calcination occurred only with direct exposure to live coals analysis by infra red spectroscopy reveals that marked changes in crystallinity accompany the macroscopic transformations in colour and friability of modern fire altered bone specifically a monotonic non linear decrease in mean fragment length across six colour categories was observed when samples were agitated or trampled and a concordant decline in bone identifiability first with respect to skeletal element and ultimately the recognizability of bone tissue itself these findings help qualify the behavioural and taphonomic implications of fragmented burned bones in archaeological sites especially with regard to potential stratigraphic associations between artefacts and hearth features in sites and the intensity of space use by human occupants the identification of burning damage on archaeological bone is a separate issue however it was found that the molecular signatures of recrystallization in modern burned bones partly overlap with recrystallization caused by weathering after only 1 to 2 years of exposure in an arid setting and by partial fossilization of archaeological bones over the long term while infra red and x ray diffraction techniques effectively describe heat induced changes in modern bone mineral and are an important aid for modelling diagenetic processes these techniques did not reliably identify burning damage to archaeological bones cross referencing readily visible colour phases with hcl insoluble fraction data proves much more effective and economically feasible for the latter purpose

benthic foraminifer palaeoecology of the late quaternary continental outer shelf of a landlocked marine basin in central aegean sea greece abstract north evoikos gulf greece constitutes a landlocked epicontinental and semi enclosed basin connected to the central west aegean sea through a strait probably not allowing full exchange of intermediate and deep water masses benthic foraminifer analyses were carried out on a late quaternary core from the outer shelf of the basin with the aim of tracing palaeoceanographic changes the benthic foraminifer species percentage per sample was used to calculate two main biological proxies the benthic foraminifer oxygen index bfoi and benthic foraminifer high productivity bfhp proxy estimated by grouping benthic foraminifer taxa which are known to flourish under high corg flux the estimated values of bfhp and bfoi were controlled mainly by the abundance of bolivinid species which are generally considered as opportunistic and shallow infaunal species tolerant to low oxygen conditions the statistical analysis q mode cluster analysis singled out four time intervals each characterized by certain levels of oxygenation and food availability time interval 1 8513 8300 cal bp is characterized by a mixed fauna of oxyphilic taxa and taxa that live in suboxic environment indicating the existence of a relatively eutrophic system with a well oxygenated sediment water interface time interval 2 8300 8100 cal bp records a deterioration of conditions on sea floor testified by significant oxygen and biotic diversity decrease benthic foraminifer composition in time interval 3 8100 7000 cal bp depicts environmental conditions still highly variable yet with faunal indication of more stable conditions than during the previous interval finally the benthic foraminifer assemblage of time interval 4 7000 3500 cal bp is related to the high food supply and good bottom circulation the data suggest a strong linkage between the quantity and quality of the organic matter supplies and the diversity and composition of the benthic foraminifer faunas moreover this study clearly demonstrates that vertical tectonic movements need to be taken into account when reconstructing the late quaternary palaeoceanography of this region

late holocene deep sea benthic foraminifera from the sea of marmara abstract the benthic foraminiferal assemblages of two cores from the late holocene organic carbon rich and carbonate poor deep sea sediments of the eastern depression of the sea of marmara have been studied they were deposited under high level of primary productivity and poorly oxygenated bottom water conditions they show low diversity and are dominated by a group of species adapted to an infaunal life style with wide bathymetric distribution ca 70 2000 m in the mediterranean sea oxygen deficiency down to about 0 5 ml l does not seem adversely to affect the rate of reproduction of the dominant species belonging to melonis chilostomella buliminids and bolivinitids their distribution is primarily controlled by substrate conditions faunal similarities with fossil assemblages in association with some late quaternary sapropels and related facies from the eastern mediterranean basins suggest that they were deposited under palaeo oceanographic conditions closely similar to those of the modern sea of marmara

inner core transition zone and anomalous pkp df waveforms from polar paths 1 short period pkp df waves which travel through the inner core from polar paths nearly ns were observed to have small amplitudes and complex waveforms but the cause has been a mystery here we examine both short period and broadband pkp record sections from a single earthquake in south sandwich islands ssi the data from polar paths show clear evidence for an inner core triplication our waveform modeling suggests a 250 km thick isotropic upper inner core uic overlying an anisotropic lower inner core lic with about 8 anisotropy the synthetics match the observed waveforms and amplitudes well with a normal value of inner core attenuation we propose that such a uic lic transition zone structure may be the cause of anomalous df waveforms along polar paths the inferred level of anisotropy in the lic 2 3 times previous estimates has important implications for understanding physical properties of the inner core and sources of inner core anisotropy

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

45 610 52 160 years of site and landscape occupation at nawarla gabarnmang arnhem land plateau northern australia we present bayesian modelling on a long sequence of radiocarbon ages from the archaeological site of nawarla gabarnmang central arnhem land plateau northern australia a horizon of wind borne sediments containing flaked stone artefacts and charcoal commencing 45 610 cal bp the young end of the modelled boundary age range which extends beyond the limit of the calibration curve with a median modelled age of 48 500 cal bp signals the onset of aeolian mobilisation of fine sands and silts across the landscape and re deposition within the site at a time synchronous with the first evidence of people this earliest cultural horizon stratigraphic unit 4 contains 509 stone artefacts and is marked by a contemporaneous sedimentary break from underlying culturally sterile sediments consisting of disintegrating roof fall and in situ sandstone and quartzite to overlying culturally rich wind blown sand the new radiocarbon ages and wind blown sediments together provide evidence for the commencement of noticeable landscape burning on the arnhem land plateau c 48 500 cal bp suggesting an intensification of landscape management practices at the summit of the arnhem land plateau some 10 000 e15 000 years after the lowest dense band of artefacts phase 2 at madjedbebe on the floodplains 90 km to the north these results have ramifications for the structure and timing of the spread of people across australia and the extinction of megafauna in sahul

late glacial to holocene benthic foraminifera in the marmara sea implications for black sea mediterranean sea connections following the last deglaciation benthic foraminifera were studied from four gravity cores that penetrated holocene marine sediments in the marmara sea morphogroup and assemblage analyses reveal that the holocene sea level rise did not result in a catastrophic flooding event as proposed by w b f ryan and others whereby well oxygenated saline mediterranean waters rapidly inundated a low lying low salinity black sea lake at v7 15 ka popularly known as the noah s flood hypothesis rather the benthic foraminiferal data confirm the hypothesis that the dardanelles sill was breached by the mediterranean at v12 ka allowing saline waters to penetrate the marmara sea these saline waters reached the level of the bosphorus sill at v9 5 ka but were unable to penetrate into the black sea until after v9 1 ka because of the persistent strong outflow of brackish to fresh water from the black sea the initial colonisation of the marmara sea by benthic foraminifera is essentially synchronous with the re establishment of marine connections through the dardanelles strait at v12 ka by v10 ka ammonia dominated faunas developed on the strait exit delta v1 at the southern end of the bosphorus and at v9 1 ka the appearance of fully marine species documents the establishment of a more stratified water column over v1 finally the increase in abundance of planktonic foraminifera at the southern exit of the bosphorus after v6 1 ka reflects a decreased volume of outflow water from the black sea quantitative analysis of benthic foraminiferal morphogroups reveals that the oxygen content of subhalocline water was low below v1 5 ml l throughout the holocene and the occurrence of sapropel sediment in the deeper part of the basin suggests bottom waters may have been anoxic at times after v4 5 ka an increase in benthic foraminiferal oxic morphotypes suggests a reduction in black sea outflow and weakening of the halocline the strong and persistent stratification of the water column in the marmara sea throughout the holocene is entirely incompatible with the noah s flood hypothesis 2002 elsevier science b v all rights reserved

anisotropy in central part of inner core the anisotropy in the central part of the inner core has been difficult to study because of the paucity of pkp data at antipodal distances especially for those paths running nearly north south polar paths in this paper we systematically search through the international seismological center isc picks of pkikp travel times for polar paths at near antipodal distances reported recently by su and dziewonski 1995 corresponding seismograms were obtained from the worldwide standardized seismographs network wwssn film chip library at lamont doherty earth observatory by using seismograms we can impose quality control on the data measure differential times ab df in this case by cross correlation and use long period waveforms if available nonpolar paths at near antipodal distances are assembled as well to address biases from lateral variation in the lowermost mantle on ab df times our results show large ab df residuals of 2 to 8 s for the polar paths at near antipodal distances moreover the absolute df travel times for the polar paths exhibit fast anomalies of the same magnitude relative to nonpolar paths while ab times show no obvious difference between polar and nonpolar paths these observations are consistent with an axisymmetric anisotropy of 3 around the spin axis throughout the bulk of the inner core with the possibility of even stronger anisotropy near earth s center this degree of anisotropy is still greater than what the most recent models based on normal modes would indicate

temporal variations in sedimentation patterns nw aegean sea abstract cores are examined from the northern continental slope environment of the sporadhes basin the western part of the north aegean sea trough three distinct lithofacies have been identified which correspond with similar environments identified elsewhere in the western and southeastern mediterranean these layers turbiditic mud hemipelagic mud calcareous ooze represent late quaternary climatic and eustatic sea level changes and tectonic activity based on benthic foraminiferal evidence from the eastern part of the north aegean sea trough it is suggested that contemporary sediment supply and physical oceanographic conditions in the area under investigation might be conducive to sapropel formation also that the depositional sequence in the cores represents a gradual recovery in the mediterranean sea since its last stagnation and sapropel formation some 8000 years ago

a 28 000 year old excavated painted rock from nawarla gabarnmang northern australia we report new archaeological excavations from northern australia revealing part of a charcoal design likely to be c 28 000 years old and chrono stratigraphically constrained within the period 15 600 45 600 cal bp on a small rock slab fallen from the ceiling at the rockshelter of nawarla gabarnmang in jawoyn country arnhem land this represents the oldest confirmed pictograph in australia

a lower mantle s wave triplication and the shear velocity structure of d summary a lower mantle s wave triplication detected with short and longperiod wwssn and csn recordings indicates a substantial shear velocity discontinuity near 280 km above the core mantle boundary the triplication can be observed in rotated sh seismograms from intermediate and deep focus events throughout the distance range from 70 to 95 three distinct source region receiver array combinations that have been investigated in detail demonstrate consistent travel time and relative amplitude behaviour of the triplication with slight systematic shifts in the triplication indicating up to 40km variations in the depth of the discontinuity modelling of the observations with synthetic seismograms produced with the cagniard de hoop and reflectivity methods constrains the shear velocity increase to be 2 75 k 0 25 per cent comparable to upper mantle discontinuities short period observations indicate that the velocity increase may be a sharp first order discontinuity or may extend over a transition zone no more than 50 km thick the shear velocity gradient below the discontinuity within the d layer is not well constrained by the sh data but slightly positive or near zero velocity gradients are consistent with the long period amplitude ratios of scsh sh

black sea impact on the formation of eastern mediterranean sapropel s1 evidence from the marmara sea abstract water exchange between the black sea and the mediterranean sea has been a major focus of the paleohydrography of the eastern mediterranean glacial melt water released from the black sea is a potential factor in the formation of sapropel s1 an organic rich sediment layer that accumulated during the early holocene a high resolution study done on sediments from the marmara sea the gateway between the mediterranean and the black sea sheds light on the holocene exchange processes past sea surface temperature and sea surface salinity sss were derived from stable oxygen isotope ratios 18o of foraminiferal calcite and alkenone unsaturation ratios uk 37 heavy 18o values and high sss in the marmara sea suggest absence of low salinity water from the black sea during s1 the comparison with data from the levantine basin and southern aegean sea outlines gradients of freshening in the eastern mediterranean sea whereby the major sources of freshwater were closer to the levantine basin it is thus concluded that the black sea was not a major freshwater source contributing to formation of s1 given the absence of a low salinity layer the deposition of organic rich sediments corresponding to s1 in the marmara sea is likely the result of the global transgression and the concomitant re organization of biogeochemical cycles leading to enhanced productivity as shown by globigerina bulloides

paleoenvironments of the marmara sea turkey coasts from paleontological and sedimentological data abstract the faunal composition of upper pleistocene holocene sedimentary sections was investigated from several boreholes in the coastal areas of the northern and eastern marmara sea the boreholes penetrated to pre quaternary basement and contain sediments deposited in near shore environments such as lagoons estuaries and deltas during the post glacial transgression rapidly rising sea level drowned these littoral areas progressively transforming into their present form over the last 9 5 10 ka bp uncalib thus the lower kucukcekmece valley became a lagoon while the golden horn became an estuary on the northeast coast the kurbagali delta was submerged when the rate of sea level rise decreased at about 5000 6000 years ago the influence of mediterranean water on the faunal assemblage was surpassed by salinity tolerant forms probably due to increased freshwater and sediment input on land

climatic forcing of eastern mediterranean deep water formation and benthic ecosystems during the past 22 000 years abstract lateglacial and holocene faunal and stable isotope records from benthic foraminifers in the eastern mediterranean sea ems suggest a high spatiotemporal variability of deep water oxygenation and biogeochemical processes at the sea floor during that time changes in the oxygenation and food availability of the deep sea ecosystems are closely linked to the hydrology of the ems borderlands they reflect orbital and suborbital climate variations of the high northern latitudes and the african monsoon system during the last glacial maximum cool surface waters and high evaporation resulted in maximum convection and oxic deep waters in all sub basins strong wind induced mixing fostered surface water production with seasonal phytodetritus fluxes during the glacial termination and the holocene oxygenation and food availability of deep sea benthic ecosystems were characterized by a pronounced regional differentiation local deep water formation and trophic conditions were particularly variable in the northern aegean sea as a response to changes in riverine runoff and black sea outflow during the interval of sapropel s1 formation in the early holocene average oxygen levels decreased exponentially with increasing water depth suggesting a basin wide shallowing of vertical convection superimposed by local signals in the northernmost aegean sea deep water ventilation persisted during the early period of s1 formation owing to temperature driven local convection and the absence of low salinity black sea outflow at the same time severe temporary anoxia occurred in the eastern levantine basin at water depths as shallow as 900 m this area was likely influenced by enhanced nutrient input of the nile river that resulted in high organic matter fluxes and related high oxygen consumption rates in the water column in the southern aegean and levantine seas we observe a gradual increase in deep water residence times preceding s1 formation by approximately 1 1 5 kyr once oxygen levels fell below a critical threshold the benthic ecosystems collapsed almost synchronously with the onset of s1 deposition the recovery of benthic ecosystems during the terminal phase of s1 formation is controlled by subsequently deeper convection and re ventilation over a period of approximately 1500 years after the re ventilation of the various sub basins had been completed during the middle and late holocene deep water renewal was more or less similar to recent rates during that time deep sea ecosystem variability was driven by short term changes in food quantity and quality as well as in seasonality all of which are linked to millennial scale changes in riverine runoff and associated nutrient input

early human occupation at devil s lair southwestern australia 50 000 years ago abstract new dating confirms that people occupied the australian continent before the earliest time inferred from conventional radiocarbon analysis many of the new ages were obtained by accelerator mass spectrometry 14c dating after an acid base acid pretreatment with bulk combustion aba bc or after a newly developed acid base wet oxidation pretreatment with stepped combustion abox sc the samples charcoal came from the earliest occupation levels of the devil s lair site in southwestern western australia initial occupation of this site was previously dated 35 000 14c yr b p whereas the aba bc ages are indistinguishable from background beyond 42 000 14c yr b p the abox sc ages are in stratigraphic order to 55 000 14c yr b p the abox sc chronology suggests that people were in the area by 48 000 cal yr b p optically stimulated luminescence osl electron spin resonance esr ages u series dating of flowstones and 14c dating of emu eggshell carbonate are in agreement with the abox sc 14c chronology these results based on four independent techniques reinforce arguments for early colonization of the australian continent

regional seismic variations in the inner core under the north pacific an asymmetry between a nearly isotropic faster eastern hemisphere and an anisotropic slower western hemisphere in earth s inner core has been revealed by previous seismic studies however it remains unclear if division of the inner core into just two hemispheres is too simplistic here we carry out regional scale tomography using a new body wave data set to study the hemisphere boundary region beneath the northern and central pacific ocean and north america if anisotropy is not considered then a hemispherical pattern seems to be present in the study region though the hemisphere boundary appears to be irregular however once the presence of anisotropy is permitted we find that this region cannot be simply separated into an anisotropic western hemisphere and an isotropic eastern hemisphere instead the strength of the anisotropy varies regionally the global hemispherical pattern is not observed here instead the strongest anisotropy is observed in the centre and south west of the study region some of the strongest anisotropy appears to be in the eastern inner core while part of the inner core assumed to be in the western hemisphere shows weaker anisotropy thus this part of the inner core displays complex variations in anisotropy which differ from a simple hemispherical division we suggest that a long lived global heterogeneity such as uneven heat flow through the core mantle boundary over a period of hundreds of millions of years may be responsible for the observed pattern of inner core anisotropy

redating the onset of burning at lynch s crater north queensland implications for human settlement in australia lynch s crater preserves a continuous high resolution record of environmental changes in north queensland this record suggests a marked increase in burning that appears to be independent of any known major climatic boundaries this increase is accompanied or closely followed by the virtually complete replacement of rainforest by sclerophyll vegetation the absence of any major climatic shift associated with this increase in fire frequency therefore has been interpreted as a result of early human impact in the area the age for this increase in burning on the basis of conventional radiocarbon dating was previously thought to be approximately 38000 c 14 yr bp supporting the traditional model for human arrival in australia at 40 000 c 14 yr bp here we have applied a more rigorous pre treatment and graphitisation procedure for radiocarbon dating samples from the lynch s crater sequence these new dates suggest that the increase in fire frequency occurred at 45 000 c 14 yr bp supporting the alternative view that human occupation of australia occurred by at least 45 000 55 000 cal yr bp copyright c 2001 john wiley sons ltd

geochemical studies of the recent sapropel and associated sediment from the hellenic outer ridge eastern mediterranean sea i mineralogy and chemical composition abstract the mineralogy major and minor element geochemistry and the accumulation rate of a single kastenlot core from the eastern mediterranean is reported the sapropel is similar mineralogically and in its major element composition to the associated marl ooze and calcareous clay it differs from these sediments in having higher concentrations of ba cr cu mo ni sr and zn and lower concentrations of mn the enrichments are explained by increased fertility ba organic matter or sulphide association cr cu mo ni and zn and the presence of aragonitic pteropods sr the organic material has a marine origin based on the carbon isotopic value 13 c 20 and c n ratio 10 the sapropel accumulated 3 to 5 times faster than the associated sediments in this particular core the evidence is consistent with the formation of this sapropel by an increased flux of carbon to the sea floor this would have been caused by increased marine primary production in the eastern mediterranean during periods of reversed circulation brought about by high post glacial runoff primarily from northern africa the additional carbon flux would have lowered the oxygen levels of the bottom waters but it is not known whether anoxic conditions ensued or whether they would have been necessary to preserve the deposited carbon

stable isotope composition of benthic foraminifera from the equatorial pacific when ranked according to deviation from isotopic equilibrium deep sea benthic foraminifera exhibit no correlation between the rankings for oxygen and for carbon both rank sequences are stable from east to west in the equatorial pacific fertility independent and from glacial to post glacial time independent records for the past 15 000 yr suggest marked changes in deep sea circulation during this time interval

living stained deep sea foraminifera from the sea of marmara a preliminary study abstract in this preliminary study we investigate living stained foraminifera from the sea of marmara we focus on the faunal composition and geochemical signatures trace elements carbon and oxygen stable isotopes in foraminiferal tests at two deep sea sites 329 and 1240 m depth respectively documented by rov observations and sampling both study areas are heterogeneous including bacterial mats and carbonate concretions proximal to cold seeps and consist of dysoxic bottom water o2

tomographic inversion for three dimensional anisotropy of earth s inner core abstract seismological studies generally suggest that the earth s inner core is anisotropic and the anisotropic structure changes significantly both laterally and with depth previous body wave studies of the inner core have relied on ray tracing or waveform modeling using one dimensional 1d models here we present non linear tomographic inversions of the inner core anisotropy using three dimensional 3d ray tracing spline parameterization and a large collection of pkp differential travel times we adapt a pseudo bending ray tracing pbr method in spherical coordinates for seismic rays that traverse the inner core pkp df phase the method iteratively perturbs each discontinuity point and continuous segment of the ray through 3d earth structure so that its travel time is minimum the 3d anisotropic structure of the inner core is approximated to the first order as 3d heterogeneous but isotropic structure for a given ray the data are corrected using a scaled mantle tomographic model the inner core anisotropy model obtained has the following major features 1 the model has strong hemispherical and depth variation the isotropic velocity in the topmost inner core is greater in quasi eastern hemisphere qeh 40 160 e than in quasi western hemisphere qwh other longitudes the anisotropy is weak in qeh to the depth of 600 700 km below the inner core boundary icb while in qwh the anisotropy increases at much shallower depth about 100 200 km below the icb to about 3 4 then remains at about 2 4 throughout the rest of the inner core 2 the anisotropy form changes abruptly over a depth range of about 150 km at the radius of about 600 km slightly less than half of the inner core radius forming a distinct inner inner core iic the velocity in the iic has maximums at equatorial and polar directions and minimum at an angle of about 40 from the equatorial plane the velocity in the outer inner core oic however changes little for ray directions 0 40 from the equatorial plane 3 despite large variation of the anisotropy the isotropic velocity voigt average throughout the inner core is nearly uniform the results suggest that the oic is likely composed of the same type of iron crystals with uniform chemistry but the iic may be composed of a different type of crystal alignment a different iron phase or a different chemical composition our tests on model parameterization mantle correction and linear and non linear inversion suggest the main features of our model are very robust however fine scale structures are likely to differ particularly in the major transition zones e g in the topmost qwh isotropy to anisotropy between oic and iic change in the form of anisotropy and between qeh and qwh in oic difference in anisotropy strength searches for possible waveform complications from these boundaries need to be aware of the directional dependence and geographical variation to be successful

inner core rotation rate from small scale heterogeneity and time varying travel times the time it takes seismic waves to propagate from south atlantic earthquakes through the inner core to station col in alaska has decreased systematically over the past 30 years travel times from three earthquakes in 1991 to an array of 37 seismometers in alaska suggest that lateral gradients in seismic wavespeeds are steep in this part of the inner core this combination of observations can be explained by postulating that the inner core is rotating 0 2 to 0 3 per year faster than the mantle

observational evidence for diffracted sv in the shadow of the earth s core on the basis of observational evidence it has been assumed for a long time in the seismological literature that the diffracted s wave in the deep shadow of the earth s core is polarized as sh in good agreement with models that do not contain a well pronounced low velocity zone at the base of the mantle while this seems often to be the case broad band horizontal records from the geoscope network show that for some wavepaths the diffracted sv is strong enough to be clearly observed at distances between 107 and 117 moreover in some cases the diffracted sv is shifted with respect to sh by approximately a quarter period such observations should put additional constraints on the structure near the core mantle boundary among other possibilities lateral variations of the gradient at the base of the mantle allowing for regions with negative gradient and possibly azimuthal anisotropy in d should be considered in order to explain these data

small scale structure of the geodynamo inferred from oersted and magsat satellite data the geodynamo in the earth s liquid outer core produces a magnetic field that dominates the large and medium length scales of the magnetic field observed at the earth s surface1 2 here we use data from the currently operating danish oersted3 satellite and from the us magsat2 satellite that operated in 1979 80 to identify and interpret variations in the magnetic field over the past 20 years down to length scales previously inaccessible projected down to the surface of the earth s core we found these variations to be small below the pacific ocean and large at polar latitudes and in a region centred below southern africa the flow pattern at the surface of the core that we calculate to account for these changes is characterized by a westward flow concentrated in retrograde polar vortices and an asymmetric ring where prograde vortices are correlated with highs and retrograde vortices with lows in the historical 400 year average magnetic field4 5 this pattern is analogous to those seen in a large class of numerical dynamo simulations6 except for its longitudinal asymmetry if this asymmetric state was reached often in the past it might account for several persistent patterns observed in the palaeomagnetic field7 8 9 10 we postulate that it might also be a state in which the geodynamo operates before reversing

new radiocarbon dating of the transition from the middle to the upper paleolithic in kebara cave israel the middle to upper paleolithic transition mp up transition is considered a major technological and cultural threshold at the time when modern humans spread out of africa expanded from the levant into europe and possibly into central and northern asia the dating of this techno cultural transition has proved to be extremely difficult because it occurred sometime before 40 000 radiocarbon years before present 14c years bp which is close to the end of the effective dating range of radiocarbon other dating methods such as thermoluminescence tl or electron spin resonance esr are not sufficiently precise to date the recorded archaeological mp up transition in the levant here we report a consistent set of stratified radiocarbon ages on freshly excavated charcoal from kebara cave mt carmel israel that span the late middle paleolithic mp and early upper paleolithic eup this study applied novel strategies to improve sample preparation techniques and data analysis to obtain high resolution radiocarbon models from this study it is proposed that the mp up transition for this site can be placed immediately after 45 200 700 14c years bp and before 43 600 600 14c years bp or from 49 48 to 47 46 radiocarbon calibrated years before present years cal bp

new constraints on the structure of the inner core from p p we measured absolute p p df as well as differential p p bc p p df and p p ab p p df travel time residuals for earthquakes in alaska and the aleutians recorded at norsar array norway for such paths p p df samples two regions of the inner core which have been identified as strongly anisotropic 3 5 respectively beneath the central pacific and africa and should arrive some 6s earlier than predicted by a standard model absolute and differential travel times do not appear to be anomalous a very complex texture and or heterogeneity of the top 400km of the inner core or a significant contribution from the strongly heterogeneous d is required to explain this discrepancy

joint inversion for inner core rotation inner core anisotropy and mantle heterogeneity observational evidence for differential rotation of the inner core has recently been reported from time dependent travel times of the seismic inner core phase pkp df these analyses are hindered by potential biases from the mantle heterogeneity and systematic earthquake location errors which have raised doubts about the reality of the inferred differential rotation here we report time dependent pkp df pkp bc differential travel times of a total of 611 measurements obtained from 92 earthquakes in the south sandwich islands ssi over the past nearly half a century recorded at the college alaska station col and alaska seismic network asn the events are relocated using the joint hypercenter determination jhd technique dewey 1971 travel time residuals at col from ssi earthquakes over a period of 45 years and at three additional stations from ssi earthquakes over periods of about 22 years show steady increases with time the temporal trends are demonstrated to be statistically very significant with dense samples of the pathway at different time periods we use a joint inversion technique that allows us to separate the time dependent inner core structure from the time independent mantle biases surprisingly the inner core rotation seems resolvable even from digital data observed at asn in the 1990s spanning over 8 years alone in such a joint inversion the results provide strong support for a differential inner core rotation the inferred rotation rate ranges from 0 3 to 1 1 per year faster than the mantle when we take into account the uncertainty in the tilt of the anisotropy axis of the patch of the inner core that was sampled a westward inner core rotation can be ruled out

foraminiferal record and environmental changes during the deposition of the early middle pleistocene sapropels in southern italy a foraminiferal investigation documents the palaeoenvironmental changes across the sapropel units associated with insolation cycles 90 and 86 in the early middle pleistocene im fosso 5 agosto section basilicata southern italy three benthic foraminiferal fossil associations associations a b and c identified by performing hierarchical cluster analysis on the quantitative data can be considered diagnostic of the palaeoenvironmental conditions before during and after the sapropel intervals they indicate a gradual decrease of bottom water oxygenation prior to the onset of sapropel deposition and a rapid return to stable environmental conditions at the end of the sapropel events the constant presence of benthic foraminifera throughout the sapropels implies that the bottom environment was not totally anoxic the high resolution distributional pattern of planktonic and benthic foraminifera within the sapropel associated with i cycle 90 documents a surface water cooling with consequent rapid re oxygenation of bottom waters that subdivides this interval in two phases both of them are characterized by an early subphase with warm climate conditions a decrease of salinity in surficial water layers and dominated by the low oxygen tolerant benthic species globobulimina affinis the late subphase shows thermal stratification during summer and a relatively deep and oxygenated mixed layer during winter in this subphase the contemporaneous replacement of g affinis the bless opportunistic but more resistant to low oxygen conditionsq species with bolivina alata bolivina dilatata and brizalina spathulata the bless resistant to low oxygen conditionsq species indicates the relative oxygen improvement in sediment pore water the frequent changes detected in the sapropel associated faunal composition underline the unstable nature of bottom water oxygen content d 2004 elsevier b v all rights reserved

biostratigraphic implications for the turbidite depositional processes on the monterey deep sea fan central california abstract recognition of the pleistocene holocene boundary and biohorizons on the continental margin of california is complicated by turbidite deposition the coiling ratio of neogloboquadrina pachyderma ehrenberg the relative frequencies of subarctic and transitional planktonic foraminifers radiolarian number and the radiolarian foraminiferal ratio all show variability in upper quaternary sections that appear related to downslope transport processes in addition to the environment of surface waters and carbonate dissolution we examined the distribution of microfossils in ten turbidites from the western levee of the monterey fan to determine 1 how turbidite microfossil assemblages differ from those of hemipelagic intervals 2 if turbiditic muds can be distinguished from hemipelagic muds based on fossil content and 3 if microfossils used to define biostratigraphic zones are significantly affected by turbiditic processes using cluster analysis samples were successfully divided into hemipelagic and turbiditic groups based on the relationship among five of 16 variables cluster a sand content the relative frequency of shallow water benthonic foraminifera benthonic foraminiferal number adjusted benthonic foraminiferal number and the relative frequency of dextral neogloboquadrina pachyderma ehrenberg the variables jointly characterize a transitional assemblage transported from a bathyal or neritic source both radiolaria and planktonic foraminifera are used to mark biohorizons on the california continental margin in this study it was found that both fossil groups vary significantly in concentration and relative frequency between turbiditic and hemipelagic muds of the monterey fan and microfossil assemblages are measurably different between tops and bases of turbidites the coiling ratio of neogloboquadrina pachyderma ehrenberg varies the least and may be most resistant to bias by hydraulic sorting and differential carbonate preservation related to transport processes

sharpness of the hemispherical boundary in the inner core beneath the northern pacific abstract the hemispherical nature of heterogeneities of the isotropic velocity and attenuation of the inner core has been extensively studied by seismic observations but consensus on the character of the boundary between two hemispheres has not yet been achieved to investigate the hemispherical boundary in detail we analyze core phase data whose ray paths propagate beneath the northern pacific we employ a waveform inversion approach based on simulated annealing to measure the differential traveltime and the attenuation parameter of the core phases measured differential traveltimes for data from european stations for events in the fiji tonga region show positive anomalies consistent with the eastern hemisphere model while those from usarray for events in indonesia show relatively small values ray theory based forward modeling of the differential traveltimes is conducted by varying the shape and the transition width of the boundary an arc like shape boundary that connects points 0 n 159 w on the equator and 79 n 110 e in far north with a transition width of 600 km best explains the observed differential traveltimes rather than a sharp boundary this model also accounts for the observed variation of attenuation parameters

low salinity surface water incursions across the strait of sicily during late quaternary sapropel intervals abstract sapropel layers black organic rich sediments in the deep eastern mediterranean basin are indicators of anoxic conditions that occurred intermittently during the pleistocene during these times of deep water stagnation the surface waters were marked by changes in planktonic foraminiferal assemblages indicative of reduced salinity previous work has established a strong link between low salinity surface waters and glacial meltwater inflow into the eastern mediterranean via the black sea discriminant analysis was applied to foraminiferal abundance data from the sapropelcontaining core lynch ii 3 collected in 2400 m water depth approximately 80 km east of the strait of sicily the function produced is 98 effective at distinguishing the faunal assemblages in non sapropel sediments from those associated with four sapropel layers in this core the most distinctive characteristic of the sapropel faunas is a high percentage of neogloboquadrina dutertrei the discriminant function has been applied to a suite of cores from the strait of sicily that lack sapropels because the strait maximum depth of 1700 m has remained continuously aerated this analysis has distinguished planktonic foraminiferal assemblages and associated sediments coeval with sapropel formation in the deeper eastern basin these correlations are supported by planktonic foraminiferal biostratigraphy and a distinctive ash layer in core lynch ii 3 and two cores from the strait existence of the sapropel assemblage in core tr171 11 from the western entrance of the strait indicates that low surface salinities extended through the strait a condition requiring a surface water flow from east to west a reversal of the present day circulation pattern

last glacial megafaunal death assemblage and early human occupation at lake menindee southeastern australia abstract the tedford subfossil locality at lake menindee preserves a diverse assemblage of marsupials monotremes and placental rodents of the 38 mammal taxa recorded at the site almost a third are of extinct megafauna some of the bones are articulated or semi articulated and include almost complete skeletons indicating that aeolian sediments rapidly buried the animals following death new optical ages show the site dates to the early part of the last glacial 55 700 1300 yr weighted mean age this is close to the 51 200 39 800 yr australia wide extinction age for megafauna suggested by roberts et al 2001 science 292 1888 1892 but like all previous researchers we cannot conclusively determine whether humans were implicated in the deaths of the animals although an intrusive hearth at the site dating to 45 100 1400 yr ago is the oldest evidence of human occupation of the darling river no artifacts were identified in situ within the sub fossil bearing unit non anthropogenic causes such as natural senescence or ecosystem stress due to climatic aridity probably explain the mortality of the faunal assemblage at lake menindee

pkp bc df travel time residuals and short scale heterogeneity in the deep earth differential pkp bc pkp df travel time residuals for quasi polar paths in the earth present large excursions from the trends predicted by simple models of inner core anisotropy we analyze a set of such paths classified according to specific source and station regions and show that observations are compatible with a constant anisotropy model of at most 1 5 in the outer 400 km of the inner core to explain local departures of up to 3 sec from the predictions of such a model strong lateral variations on scale lengths shorter than a few hundred km need to be invoked either in the core or in the mantle independent results of d modelling argue in favor of an important contribution from the latter

d discontinuity structure beneath the north atlantic from scd observations we analyzed transverse and radial component recordings from the 2010 m6 3 southern spain earthquake depth 620 km recorded on 370 broadband stations in north america we grouped these seismograms into subarrays and applied fourth root vespa processing vespagram analysis in order to enhance low amplitude arrivals these vespagrams show clear scd arrivals which indicate the existence of the d discontinuity beneath the north atlantic ocean 45 60 n 45 55 w these observations are best fit with a 2 4 velocity increase at the top of the d discontinuity at a height above the core mantle boundary of 304 14 km we do not observe scd arrivals at the eastern end of our study region which is consistent with the presence of the easternmost edge of the ancient farallon plate

deep sea ecosystem variability of the aegean sea during the past 22 kyr as revealed by benthic foraminifera abstract specific responses of the regional deep sea ecosystems to climatic and oceanographic processes during the last 22 kyr are revealed by benthic foraminiferal faunas from two cores in the northern and southern aegean sea under glacial boundary conditions high diversity benthic foraminiferal faunas and elevated benthic foraminiferal numbers indicate enhanced organic matter availability and well ventilated deep water masses in the whole aegean sea the glacial termination is accompanied by significant fluctuations in productivity and deep water ventilation in the northern aegean sea meltwater inflow from mountain glaciers during the bolling allerod warm period resulted in a restriction of local deep water formation as mirrored by a dominance of bolivinids during the deposition of sapropel s1 drops in benthic foraminiferal number and diversity are more significant in the southern aegean sea when compared to the north this suggests the persistence of local deep water formation in the northern aegean sea during s1 deposition in addition faunal fluctuations within s1 at both sites suggest the repeated influence of short term cooling events on the re ventilation and re colonization of aegean deep sea ecosystems during the middle and late holocene benthic foraminiferal faunas document the establishment of oligotrophic and well ventilated conditions in the southern aegean sea the corresponding faunas from the northern aegean sea reflect generally mesotrophic conditions and variable deep water oxygenation during the entire holocene the deep sea ecosystems of this region responded very sensitively to short term changes in humidity and temperature these abrupt climate changes controlled the inflow of nutrients from rivers and the black sea and the formation of local deep water masses

core structure re examined using new teleseismic data recorded in antarctica evidence for at most weak cylindrical seismic anisotropy in the inner core we present a significant addition to the data set of traveltimes of seismic pkp waves that sample the earth s lowermost mantle and core along the earth s rotation axis recorded at permanent global seismic network gsn and temporary sscua deployment broad band seismographic stations in antarctica the new data improve the previously poor and biased coverage that underlies the seismic constraints on recent models of inner core structure and anisotropy on the one hand new differential pkp traveltime measurements improve the sampling of predominantly the eastern inner core hemisphere pkpab df and pkpbc df differential traveltime residuals with respect to the spherically symmetric model ak135 are consistently smaller than two seconds along the north south paths sampled axially symmetric models of inner core seismic anisotropy with fast axis parallel to the earth s rotation axis require a weak anisotropy of 0 7 0 1 per cent to be consistent with our pkpbc df observations pkpbc df residuals from the quasi eastern hemisphere indicate 0 4 0 1 per cent anisotropy if only pkpbc df observations from the top 200 km of this hemisphere are considered this is reduced to 0 1 0 2 per cent consistent with an isotropic layer on the other hand new absolute pkp traveltime measurements add to the sampling of both hemispheres of the inner core but it is difficult to use them with more confidence to assess structure of the core since they are affected by crustal and mantle structure and source uncertainties the newly collected data set also increases constraints on d structure beneath the south pole in contrast to previous inferences based on data from northern stations we find no evidence of a velocity heterogeneity in the outer core near the inner core boundary associated with the cylinder tangent to the inner core in the southern hemisphere

hemispherical structure in inner core velocity anisotropy 1 we investigate the hemispherical pattern in inner core velocity anisotropy using a new and independent high quality data set of pkpbc pkpdf and pkpab pkpdf body wave observations our data show no evidence for a tilted anisotropy axis with respect to the earth s rotation axis and is significantly better fit by a model with 4 4 anisotropy in the western hemisphere and only 1 0 in the eastern hemisphere than by a model of uniform anisotropy we carry out variance minimization and find the boundaries between the hemispheres at lines of constant longitude at 14 e and 151 w variance minimization enables us to extract the imprint of hemispherical structure from all of the data and not just polar paths resulting in boundaries which are nearly 30 from the results of previous studies the high quality of the data allows us to provide robust evidence that the isotropic velocity in the eastern hemisphere is 0 2 lower than in the western hemisphere in the top 660 km of the inner core our data set also suggests an increase in inner core anisotropy in the eastern hemisphere from 1 to around 6 at depths deeper than 660 km indicating that the hemispherical pattern in anisotropy may disappear at greater depths the presence of hemispherical structure rules out mechanisms for creating anisotropy which are unable to sustain longitudinal variations in the inner core furthermore steady inner core superrotation of the order of 0 1 year would eradicate the hemispherical differences though inner core oscillation would still be permissible

intricate heterogeneous structures of the top 300 km of the earth s inner core inferred from global array data i regional 1d attenuation and velocity profiles abstract we apply a waveform inversion method based on simulated annealing to complex core phase data observed by globally deployed seismic arrays and present regional variation of depth profiles of attenuation and velocity for the top half of the inner core whereas measured attenuation parameters exhibit consistent trends for data sampling the eastern hemisphere of the inner core for the western hemisphere there is a remarkable difference between data sampling the inner core beneath africa w1 and beneath north america w2 obtained attenuation profiles suggest that intricate heterogeneities appear to be confined in the top 300 km the profile for the eastern hemisphere has a high attenuation zone in the top 150 km that gradually diminishes with depth conversely for the western hemisphere the profile for w1 shows constant low attenuation and that for w2 represents a gradual increase from the inner core boundary to a peak at around 200 km depth velocity profiles obtained from differential traveltimes between pkp df and pkp cd bc phases for the eastern and western hemispheres are respectively about 0 8 faster and 0 6 slower than the reference model at the top of the inner core and the difference nearly disappears at about 200 km depth our result suggests the presence of intricate quasi hemispherical structures in the top 200 300 km of the inner core

tomographic imaging of the lowermost mantle with differential times of refracted and diffracted core phases pkp pdiff the mapping of variations in p wave speed in the deep mantle is restricted by the uneven sampling of p waves in particular beneath the southern hemisphere to enhance data coverage we augmented the 1 6 million summary rays of p pp and pwp that we used in previous studies with differential travel times of diffracted and refracted core phases for the core refracted differential travel time residuals pkpab pkpdf and pkpab pkpbc we used 1383 cross correlated digital waveforms as well as 27 000 routinely processed bulletin data we used the waveform data to define quality criteria for the selection and reduction of the bulletin pkp data for pkpdf pdiff we only considered 543 records derived from waveform cross correlation no pcp data were used in this study we used optical ray theory to calculate the ray paths associated with the p pp pwp and pkp data which are measured at 1 hz however to account for the large fresnel zones of the low frequency 50 mhz pkpdf pdiff data we estimated the three dimensional shape of the frechet sensitivity kernels from kernels calculated by normal mode summation the use of these kernels allows us to properly distribute the sensitivity for a given seismic phase over a large mantle volume while allowing the high frequency data to constrain small scale structure the differential times are relatively insensitive to source mislocation and to structure in the shallow mantle beneath source and receivers and they have previously been interpreted exclusively in terms of lateral structure directly above the core mantle boundary cmb however images thus obtained can be contaminated by effects of small scale structure elsewhere in the mantle here we do not make a priori assumptions about the mantle source of anomalous time differentials from test inversions we conclude that both upper and lower mantle structures that are poorly resolved by p data can be mapped into the core along pkp paths but that the effect of outer core structures if any on the mantle model is small compared to the inversion of the p pp and pwp alone the inclusion of the pkpab pkpdf and pkpab pkpbc and pkpdf pdiff data improves the resolution of structure beneath 2200 km depth in particular the joint inversion puts better constraints on the long wavelength variations in the very deep mantle and yields an increase in the amplitude of velocity perturbations near the cmb that is in agreement with but still smaller than inferences from shear wave studies resolution tests indicate that in some regions the enhanced definition of structure is significant but in most regions the improvements are subtle and structure remains poorly resolved in large regions of the mantle

problems with radiocarbon dating the middle to upper palaeolithic transition in italy abstract radiocarbon dating of material from late pleistocene archaeological sites is challenging small amounts of modern 14c labelled contamination will significantly affect the reliability of dates from the period producing erroneous results recent developments in sample pre treatment chemistry have shown that problems in reliable age determination during this period are surmountable in this paper we provide an example of one such case from the middle to upper palaeolithic transitional site of the grotta di fumane in northern italy we ams dated two fractions of the same charcoal samples derived from a series of superimposed mousterian aurignacian and gravettian levels excavated at the site one fraction was treated using the routine acid base acid aba method the other with the more rigorous acid base oxidation stepped combustion abox sc method the latter method produced consistently older and almost certainly more reliable results the eruption of the known age campanian ignimbrite from the phlegrean fields near present day naples at 39 3 ka yr bp seals ulluzzian and proto aurignacian levels in the south of italy equivalent cultural levels are present at fumane and the results obtained with the abox sc methods are consistent with the ages inferred for sites in the south of italy based on the presence of the campanian ignimbrite new results from a sample found beneath the campanian ignimbrite at the russian site of kostenki obtained using both the aba and abox sc methods are also presented they support the conclusion reached at fumane by demonstrating that in many cases the abox sc treatment effectively removes contamination where the aba treatment does not the results of the work offer a sobering examination of the problems inherent in the current radiocarbon database relating to the period and highlight the dangers of an uncritical use of the corpus of 14c results obtained over the last few decades based on our results we predict that more than 70 of the 53 previously available determinations from fumane are erroneously young a way forward is suggested using these improved chemical preparation methods applying analytical methods to characterise the material dated and testing existing site chronologies to establish which previous determinations are liable to be inaccurate

the effect of d on pkp ab df travel time residuals and possible implications for inner core structure abstract the hypothesis that the deep inner core is anisotropic is based on pkp travel time observations at large distances and relies on a small number of very anomalous measurements for paths quasi parallel to the earth s rotation axis here we analyze a global dataset of pkp ab df travel times residuals and discuss their significant dispersion 2 s and coherent large scale patterns we show that the trends observed for quasi equatorial paths are consistent with predictions from recent tomographic mantle models when the latter are modified to account for strong heterogeneity at the base of the mantle under the pacific ocean and africa as documented in several recent studies likewise for polar paths we show that a large part of the signal could be explained by deep mantle structure the effects of complex structure in the deep mantle on pkp ab df travel times should be carefully considered in order to reliably estimate the anisotropic structure of the central part of the inner core

a comparison of geodetic and seismic estimates of inner core rotation seismological observations suggest the inner core has been rotating faster than the mantle during the past 30 50 years differential rotation can produce large gravitational torques on the mantle which if not balanced by other torques would be detectable as changes in the rotation rate of the mantle length of day or lod we compare seismological estimates of inner core rotation with estimates derived by inverting lod observations using models of gravitational coupling model predictions depend on several parameters but for the expected range of parameter values the seismological estimates of relative rotation are at least an order of magnitude larger than those predicted by the lod data furthermore the lod data predict oscillation in the angular alignment of the inner core and mantle during the past 30 50 years while the seismological data seem to require a component of steady rotation we show that steady rotation of the inner core implies a steady torque on the mantle this torque is not accelerating the rotation rate of the mantle so it must be opposed by another torque the required torque is consistent with a frictional electromagnetic stress on the base of the mantle due to a westward flow at the top of the core

lateral variations in lowermost mantle shear wave anisotropy beneath the north pacific and alaska s waves recorded by long period world wide standardized seismograph network and broadband stations in north america for deep northwest pacific subduction zone earthquakes provide evidence for anisotropy in the lowermost mantle shear velocity structure beneath the north pacific and alaska systematic delays of up to 4 s are observed between longitudinal components sv and transverse components sh of motion for core reflected scs waves as well as for core grazing and diffracted s waves the absence of significant splitting for s waves that have turning points more than a few hundred kilometers above the core mantle boundary indicates that anisotropy is localized within the d region the lowermost portion of the mantle sv sh differential arrival times for both scs and sdiff along with path length estimates assuming a 250 km thick d region indicate spatial variations in the strength of shear wave anisotropy the strongest anisotropy 1 1 5 is found in the eastern part of the study area with systematic reduction in magnitude toward the west a transverse isotropy model can explain the data with the velocity structure for horizontally polarized waves vsh having a 2 3 discontinuous shear velocity increase at the top of d as proposed in earlier studies of the region and a similar structure for s wave particle motion in the direction normal to the core mantle boundary vsv but with the velocity jump at the top of d and the velocity within d being reduced from that for vsh by 0 5 1 5 km s large uncertainties exist for velocity gradients above and below the velocity jump but the requirement of a reduced vsv relative to vsh in d is clear synthetic waveforms calculated by using separate isotropic structures for sh and sv match the observations well and constrain the basic anisotropic structure because the shear waves all traverse the region with near grazing geometries the study area exhibits strong lateral variations in lower mantle shear velocity structure and variable thickness of the d layer topography of the d layer is not well resolved because of trade off with volumetric heterogeneity

intricate heterogeneous structures of the top 300 km of the earth s inner core inferred from global array data ii frequency dependence of inner core attenuation and its implication abstract we apply a nonlinear waveform inversion method that we developed previously iritani et al 2010 iritani et al 2014 to broadband 0 02 2 hz core phase data recorded by global seismic arrays in order to investigate the frequency dependence of inner core attenuation the results show a prominent difference of the frequency dependence of attenuation between the eastern hemisphere and the western hemisphere while attenuation is frequency dependent in the western hemisphere not so in the eastern hemisphere moreover in the western hemisphere a stronger frequency dependence of the attenuation is observed beneath africa compared to beneath north america this intricate quasi hemispherical property of the frequency dependence of the inner core attenuation together with the quasi hemispherical variability of seismic velocity and attenuation strength at around 1 hz that we reported earlier can be consistently understood in terms of the relative location of the seismic observation frequency band and the absorption band peaks that are different for regions the variability of the absorption band peak may reflect the variability of the iron grain size of the inner core the grain size is larger in the eastern hemisphere than the western hemisphere and in the western hemisphere beneath north america it gradually increases with depth however caution should be taken in this inference as the physical mechanism of attenuation in the inner core is still poorly constrained both theoretically and observationally

pkp bc versus pkp df differential travel times and aspherical structure in the earth s inner core pkp bc versus pkp df differential travel times show coherent patterns of residuals indicating aspherical structure within the earth s inner core using a waveform correlation method we measure 318 differential pkp bc versus pkp df travel times from 5 years of global digital seismograph network gdsn short period data at ranges between 145 and 155 in addition we obtain 19 470 probable bc versus df travel times at these ranges by searching through 23 years of the international seismological centre isc catalog plots of residuals versus turning point location and residuals versus ray direction show clear patterns which indicate that the differential travel times are highly correlated along similar ray paths this pattern is robust with respect to range and source depth these anomalies are almost certainly due to aspherical inner core structure since pkp bc and pkp df have nearly coincident ray paths in the mantle and outer core the gdsn and isc residual patterns are in general agreement but the isc residuals underpredict the gdsn residuals by about a factor of 2 the isc data have better spatial coverage particularly for n s ray paths within the inner core these n s ray paths show positive residuals of about 0 5 s indicating faster inner core p velocities in this direction a result consistent with previous studies of absolute pkp df travel times but derived from an independent data set due to the sparse ray coverage of our data either heterogeneity or anisotropy within the inner core with about 1 velocity variations could explain these residual patterns however inversions of the isc data for heterogeneity require many more free parameters to achieve the same variance reduction as a simple two parameter anisotropy model

evidence for strong shear velocity reductions and velocity gradients in the lower mantle beneath africa we present data which indicate that the broad low shear velocity anomaly beneath southern africa is stronger and more extensive than previously thought recordings of earthquakes in the southwestern atlantic ocean at an array of broadband seismic stations in eastern africa show anomalously large propagation time delays of the shear phases s scs and sks which vary rapidly with epicentral distance by forward modeling we estimate that the low velocity anomaly extends from the core mantle boundary about 1500 km up into the mantle and that the average shear velocity within this structure is 3 lower than in standard models such as prem strong velocity contrasts exist at its margins 2 over about 300 km these seismic characteristic are consistent with recent numerical simulations of lower mantle mega plume formation

convection and anisotropy of the inner core estimation of the rayleigh number of the inner core suggests that this region is convecting the flow pattern is likely to produce crystallographic preferred orientation of the elastically anisotropic hexagonal closest packed phase of iron such that compressional wave velocities would be greater in the axial relative to the equatorial direction by roughly 1 percent this result is in agreement with seismological evidence that the inner core is elastically anisotropic

the human colonisation of australia optical dates of 53 000 and 60 000 years bracket human arrival at deaf adder gorge northern territory the date at which people entered australia has important implications for the debate on modern human origins thermoluminescence dates of 50 60 ka reported for initial occupation of the malakunanja ii site in northern australia have been used as a means of calibrating the rate of mitochondrial and nuclear dna evolution in modern humans optical dating of unburnt quartzose sediments from a rock shelter site nauwalabila i lindner site in deaf adder gorge 70 km south of malakunanja ii provides new evidence for the timing of the colonisation of the continent optical dates were determined for several stratigraphic levels within a 3 m deep excavation in which flaked stone artefacts and ground pigments were found in primary depositional setting the lowest human occupation levels are bracketed by dates of 53 4 5 4 ka and 60 3 6 7 ka while the upper levels show good agreement between optical and calibrated 14c age estimates high quality haematite with ground facets and striations is associated directly with the 53 ka level and indicates the use of pigments by these early australians the optical dates independently confirm evidence for the colonisation of northern australia shortly after 60 ka and should be seen in the context of this region as having been a likely entry route for the first human movements into sahul

holocene palaeohydrology of the east alligator river for application to mine site rehabilitation northern australia abstract as a contribution to the estimation of extreme floods and rainfall palaeofloods in the east alligator river in tropical australia were examined to derive estimates of palaeodischarges and their frequency nine extreme floods have occurred over 8400 years in a non stationary series the youngest five of which are stationary and the youngest three of which occurred during wet periods produced by variations of the southern oscillation index soi modulated by the pacific decadal oscillation pdo the magnitudes of these floods are similar with one possible exception in 2007 ce the extreme floods in the region lie close to or above the australian flood envelope curve showing that floods larger than the expected are possible their magnitudes also approximate the probable maximum flood pmf but with a much higher frequency than expected the annual exceedance probability aep of the palaeofloods is 0 3 which may also be the aep for the rainfall these results will be used as input to the design of an artificial landform at the ranger uranium mine within the east alligator catchment that has to last for 10 000 years the 2007 ce flood was probably the most extreme flood and associated rainfall likely to occur in the vicinity of ranger under the current climate and will occur in the future along with climate change because of the uncertainties associated with projections of future extremes the best design rainfall aep for the ranger landform is 0 3

seismic evidence for an inner core transition zone seismic waves that traverse earth s inner core along north south paths produce unusually broad pulse shapes at long periods compared with waves along east west paths and reflections from below the inner core boundary at short periods the observations provide compelling evidence for a seismic velocity discontinuity along north south paths about 200 kilometers below the inner core boundary separating an isotropic upper inner core from an anisotropic lower inner core the triplication associated with such a structure might be responsible for reported waveform complexity of short period inner core arrivals along north south paths and if the depth of the boundary is laterally variable their large travel time variation

heterogeneity and anisotropy of earth s inner core seismic observations provide strong evidence that earth s inner core is anisotropic with larger velocity in the polar than in the equatorial direction the top 60 80 km of the inner core is isotropic evidence for an innermost inner core is less compelling the anisotropy is most likely due to alignment of hcp hexagonal close packed iron crystals aligned either during solidification or by deformation afterward the existence of hemispherical variations used to be controversial but there is now strong evidence from both seismic body wave and normal mode observations showing stronger anisotropy less attenuation and a lower isotropic velocity in the western hemisphere two mechanisms have been proposed to explain the hemispherical pattern either a inner core translation wherein one hemisphere is melting and the other is solidifying or b thermochemical convection in the outer core leading to different solidification conditions at the inner core boundary neither is yet able to explain all se

benthic foraminiferal δ13c and accumulation rates of organic carbon uvigerina peregrina group and cibicidoides wuellerstorfi the glacial to interglacial 13c records of the benthic foraminifera cibicidoides wuellerstorfi and the uvigerina peregrina group from deep sea cores cannot be adjusted by a generally valid constant the 13c values of the u peregrina group largely correlate with the accumulation rates of organic carbon suggesting a local habitat effect those of c wuellerstorfi vary independently with respect to the carbon flux and record fluctuations in the 13c of the ambient bottom water isotopic composition

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research