marine crenarchaeotal membrane lipids in decapods implications for the tex86 paleothermometer pelagic crenarchaeota produce glycerol dibiphytanyl glycerol tetraethers gdgts as membrane lipids and the gdgt composition changes according to growth temperature this forms the basis of the tex86 paleotemperature proxy this ratio correlates with sea surface temperature sst despite the fact that crenarchaeota are distributed through the water column therefore there must be mechanisms that transport the surface signal to sediments such as repackaging in fecal pellets marine snow mass falls after phytoplankton blooms or daily migration to study gdgt transport we analyzed stomachs and intestines of atlantic and mediterranean decapods as they are one of the major megafaunal groups are easy to sample and occur in both pelagic and benthic environments gdgts were found in most decapods guts gdgt abundances are significantly lower in intestines but tex86 derived temperatures are not significantly different between stomachs and intestines 1oc suggesting that tex86 values are not altered during gut transit atlantic decapods show no difference in tex86 values between benthic detritivors and pelagic predators however mediterranean decapods show a substantial difference between macroplankton feeders and bentho pelagic predators this is probably related to the freshness of the material consumed tex86 derived temperatures in atlantic decapods are close to the sst around the time of sampling in agreement with stomach content analysis that shows fresh organic matter being ingested for mediterranean decapods tex86 temperatures are significantly higher than sst around the time of sampling this can be partly attributed to the large variability between decapod specimens and the low amounts of fresh material found in their stomachs

detection of small scale heterogeneities at the inner core boundary 2018 elsevier b v the hemispherical pattern of seismic velocities in the uppermost inner core has been described at the global scale in many studies in this paper we investigate shorter scale heterogeneities in the vicinity of the inner core boundary icb using differential travel time and amplitude measurements between the pair of core phases pkp df and pkikp seismic events occurring close to sumatra and recorded at usarray stations in the distance range 132 142 are used to investigate the velocity and attenuation structure at the icb and in the uppermost 100 km of the inner core beneath eastern russia in this distance range pkp df and pkikp are difficult to separate due to their proximity in travel time we present a new method based on the envelope of the seismic signal to identify them following which we measure differential travel time residuals and amplitude ratios by comparison with synthetics computed using the direct solution method which allows us to take into account the correct phase shift of the pkikp we found that in our region of study the compressional velocity is slower in the uppermost inner core than the ak135 model however the sampled region is located in the eastern hemisphere generally considered as faster and more attenuating than the ak135 model this suggests significant regional departures from the simple hemispherical pattern reported in the literature we also deduce from the amplitude ratios that the attenuation is stronger than the global average at the top of the inner core in this region as expected from its location in the eastern hemisphere our results confirm the presence of a low attenuation zone at the top of the inner core followed by a highly attenuating layer centered around 35 km depth in the inner core as found in the eastern hemisphere in previous studies this zone is however thinner 15 km and more attenuating q reaching values less than 50

three dimensional seismic tomography from p wave and s wave microearthquake travel times and rock physics characterization of the campi flegrei caldera 1 the campi flegrei cf caldera experiences dramatic ground deformations unsurpassed anywhere in the world the source responsible for this phenomenon is still debated with the aim of exploring the structure of the caldera as well as the role of hydrothermal fluids on velocity changes a multidisciplinary approach dealing with three dimensional delay time tomography and rock physics characterization has been followed selected seismic data were modeled by using a tomographic method based on an accurate finite difference travel time computation which simultaneously inverts p wave and s wave first arrival times for both velocity model parameters and hypocenter locations the retrieved p wave and s wave velocity images as well as the deduced v p v s images were interpreted by using experimental measurements of rock physical properties on cf samples to take into account steam water phase transition mechanisms affecting p wave and s wave velocities also modeling of petrophysical properties for site relevant rocks constrains the role of overpressured fluids on velocity a flat and low v p v s anomaly lies at 4 km depth under the city of pozzuoli earthquakes are located at the top of this anomaly this anomaly implies the presence of fractured overpressured gas bearing formations and excludes the presence of melted rocks at shallow depth a high v p v s anomaly located at 1 km suggests the presence of rocks containing fluids in the liquid phase finally maps of the v p v s product show a high v p v s horseshoe shaped anomaly located at 2 km depth it is consistent with gravity data and well data and might constitute the on land remainder of the caldera rim detected below sea level by tomography using active source seismic data

multi proxy reconstruction of terrigenous input and sea surface temperatures in the eastern gulf of guinea over the last 35 ka abstract the tight coupling between the atmospheric and oceanic circulation in the equatorial atlantic region makes this area an important region for paleoclimatic research previous studies report the occurrence of large amounts of terrigenous material and soil organic carbon soc within the marine sediments of the eastern gulf of guinea we use the accumulation rates ar of branched glycerol dialkyl glycerol tetraethers gdgts to identify variations in soc delivery to the niger fan over the last 35 ka and compare these records to long chain n alkanes as a proxy for higher plant material to an inorganic proxy for terrigenous input aluminum ar and to indicators for the marine productivity ar of carbonate and crenarchaeol in addition sea surface temperatures ssts are calculated based on the tex 86 h index and environmental factors affecting the sst reconstructions are discussed our results indicate that al ar are closely connected to the rate of mean sea level change after 15 ka bp with an additional influence of the increased monsoonal precipitation and extended vegetation cover corresponding to the african humid period 14 8 5 5 ka bp branched gdgt ar appears to be determined by shelf erosion in addition to the interplay of monsoonal precipitation and vegetation cover controlling soil erosion long chain n alkane concentrations clearly show a different trend than the other proxies which might be due to their predominant eolian transport paleo ssts show a clear shift from colder temperatures during the last glacial period 20 22 c to warmer temperatures during the holocene 24 26 c however tex 86 h based ssts are cold biased compared to recent ssts and mg ca based sst reconstructions which is probably caused by a high seasonality of the thaumarchaeota with a maximum productivity of these organisms during the cold summer months however a sub surface production of gdgts and or a potential bias of sst reconstruction by terrestrial input could not be completely excluded

plate and intraplate processes of hercynian europe during the late paleozoic abstract it is speculated that until late carboniferous time the region of hercynian europe was occupied by an elongated island arc system underlain by a segment of continental crust in the upper carboniferous two subduction zones are assumed to have extended from the north and south beneath hercynian europe an extensive zone of hot partially molten upper mantle lay above and between these and diapiric uprise of portions of this material led to separation of mafic magmas widespread partial melting in the lower and middle crust high temperature low pressure metamorphism in crustal rocks and regional uplift and extension of the crust as indicated by intermontane troughs and their associated volcanic rocks in visean to westphalian time hercynian europe collided with both the large neighbouring plates north america europe and africa during these diachronous collisions and owing to reduced rigidity of the relatively hot island arc crust the irregular continental margins of the larger and thicker continental plates induced oroclinal bending of hercynian europe after the collision processes had been terminated processes of upper mantle activity continued causing further crustal uplift and even enhanced crustal extension for several tens of million years into the lower permian decline of the upper mantle activity beneath hercynian europe is indicated by crustal subsidence and formation of a peneplain in permian time followed by the upper permian transgression of both the zechstein sea and the tethys sea which mark the end of the hercynian geodynamic cycle

paleomagnetism in the northeastern central massif france evidence for carboniferous rotations of the hercynian orogenic belt abstract a paleomagnetic study has been carried out on visean volcanics of northeastern central massif standard paleomagnetic techniques have been applied to a hundred of samples alternating field and thermal demagnetizations yield an unusual direction d 78 i 2 95 12 for the 9 best sites as the polarity is unknown two motions can explain this direction either a clockwise rotation of about 45 or an anticlockwise of 135 relative to the armorican massif in both cases the paleomagnetic data reveal important deformations of the hercynian orogenic belt probably due to strike slips in middle carboniferous times

seismic scattering and absorption mapping of debris flows feeding paths and tectonic units at mount st helens volcano abstract frequency dependent peak delay times and coda quality factors have been used jointly to separate seismic absorption from scattering quantitatively in earth media at regional and continental scale to this end we measure and map these two quantities at mount st helens volcano the results show that we can locate and characterize volcanic and geological structures using their unique contribution to seismic attenuation at 3 hz a single high scattering and high absorption anomaly outlines the debris flows that followed the 1980 explosive eruption as deduced by comparison with remote sensing imagery the flows overlay a nnw sse interface separating rocks of significant varying properties down to 2 4 km and coinciding with the st helens seismic zone high scattering and high absorption anomalies corresponding to known locations of magma emplacement follow this signature under the volcano showing the important interconnections between its feeding systems and the regional tectonic boundaries with frequency increasing from 6 to 18 hz the nnw sse tectonic feeding trends rotate around an axis centered on the volcano in the direction of the regional scale magmatic arc sw ne while the aseismic high scattering region wsw of the volcano shows no evidence of high absorption the regions of highest scattering and absorption are consistently located at all frequencies under either the eastern or the south eastern flank of the volcanic edifice from the comparison with the available geological and geophysical information we infer that these anomalies mark both the location and the trend of the main feeding systems at depths greater than 4 km

archaeal tetraether lipids record subsurface water temperature in the south china sea abstract the south china sea scs is the largest tropical marginal sea in the western pacific ocean while the u 37 k proxy is known to reflect the sea surface temperature sst of the 0 30 m mixed layer in the scs little is known about the applicability of the tex86 proxy here we present results from paired analyses of tex 86 h a modified version of tex86 and u 37 k from core top sediment samples from the scs tex 86 h based sst calculated from the global regression exhibited slightly higher values avg 28 7 c range 27 1 30 3 c than values from the world ocean atlas 1994 avg 27 4 c range 26 1 28 6 c and u 37 k based temperature values avg 27 3 c range 26 1 29 0 c moreover the linear relationship between tex 86 h and sst was poor r2 0 44 correlation analysis of tex 86 h with annual temperature and seasonal temperature at various depths revealed that tex 86 h correlated better with annual sea temperature at 30 125 m r 0 89 than with temperature in the 0 30 m mixed layer r 0 69 this suggests that tex 86 h reflects a deeper and cooler subsurface temperature rather than surface or mixed layer temperature in the scs as a result the global regression which results in higher sst values could not be applied to predict subsurface temperature in the scs and a local calibration of tex 86 h vs 30 125 m subsurface temperature was tentatively established furthermore the difference between u 37 k and tex 86 h derived temperature talkenone gdgt correlated moderately r 0 62 with the depth of the thermocline of the 18 c isotherm in the scs suggesting that the difference may provide a proxy for upper ocean vertical thermal gradient in this marginal sea

comparison of pelagic and nepheloid layer marine snow implications for carbon cycling abstract marine snow from upper and mid water i e pelagic depths on the california margin is texturally and compositionally different from that traveling in the nepheloid layer transmission electron microscopy shows that pelagic marine snow consists primarily of bioclasts e g diatom frustules foram tests organic matter and microbes these components are entrained as discrete particles or small aggregates 10 m in diameter in a loose network of exocellular muco polysaccharide material clays are infrequent but when present are constituents of comparatively compact organic rich microaggregates microbes are abundant and appear to decrease in number with increasing water depth in contrast marine snow aggregates collected from just above the sea floor in the nepheloid layer are assemblages of clay particles clay flocs and relatively dense clay organic rich microaggregates in an exocellular organic matrix bioclasts and microorganisms occur only rarely the prevalence of clay organic rich aggregates in the nepheloid layer suggests that prior to final deposition and burial marine snow from the pelagic zone is subject to disaggregation and recombination with terrigenous detrital material near or at the sea floor results have significant implications for the accumulation and burial rates of organic carbon on continental margins and the aging and bioavailability of sedimentary organic matter samples examined were collected offshore of northern and central california

glycerol dialkyl glycerol tetraethers and tex86 index in sinking particles in the western north pacific abstract seasonal and depth variation in the flux of glycerol dialkyl glycerol tetraethers gdgts and tex 86 tex 86 h and tex 86 l values in sinking particles was examined by conducting a 21 month time series sediment trap experiment at a mooring station wct 2 39 n 147 e in the mid latitude nw pacific the aim was to understand the sinking process of gdgts in the water column and the preservation of the tex 86 signal in the water column and sediment surface in the shallow trap the sinking flux of gdgts showed maxima from may 1998 to february 1999 the maximal peaks in sinking flux corresponded to peaks in the sinking flux of organic carbon opal and lithogenic material gdgt concentration in the total fine fraction and the caldarchaeol crenarchaeol ratio at three depths ca 1300 4800 m varied synchronously implying rapid vertical transport of gdgts to deeper water with a sinking velocity 260 m day 1 below ca 1300 m the changes in tex 86 based temperature were different from those in contemporary sea surface temperature sst the former was lower than the sst from may to december and corresponded to the temperature at the thermocline whereas it was higher than the sst from december to may the annual average sinking flux of the gdgts decreased with depth the gdgt half depth the depth range over which half of the gdgt is lost was calculated to be 3108 3349 m implying that gdgts were well preserved during sinking the flux weighted average tex 86 based temperature was constant with depth and corresponded roughly to mean annual sst the findings support a previous hypothesis that the gdgts produced in surface water are preferentially delivered to the deeper water column via grazing and repackaging in larger particles the constant tex 86 at different depths indicates that it was not affected by degradation in the water column the preservation efficiency of gdgts was 1 0 1 3 at the water sediment interface despite significant gdgt degradation there was a small difference in tex 86 values between sinking particles and surface sediment

subduction zones an introduction to comparative subductology abstract the subduction model for trench arc back arc systems was deduced more or less as a logical consequence of sea floor spreading many features in these systems such as thrust type inter plate earthquakes and deep earthquakes along wadati benioff zones are readily explained by the subduction model but other features such as extensional spreading and high heat flow in back arc regions and arc volcanism are difficult to explain an approach to solve these problems may be to recognize the existence of the two basically different modes of subduction one chilean type causing a compressional stress regime in the arc and back arc regions the other mariana type causing a tensional stress regime implications of the two types of the mode of subduction for some tectonic problems such as vertical movement and sediment accretion at trenches are discussed with special reference to the results of recent dsdp active margin drilling in discussing the possible causes of the two modes it is suggested that the large scale thermal and stress regimes in the back arc areas may not be the direct products of simple subduction but of some additional factors involving much greater energy such as mantle flow associated with the motion of major plates finally the possible great importance of various types of collision accretion and erosion at subduction zones is emphasized

a scattering image of campi flegrei from the autocorrelation functions of velocity tomograms summary we propose a new quantitative approach for the joint interpretation of velocity and attenuation tomography images performed through the lateral separation of scattering and intrinsic attenuation the horizontal p wave scattering attenuation structure below campi flegrei caldera cfc is imaged using the autocorrelation functions acf of p wave vertical velocity fluctuations cluster analysis ca is then applied to interpret the images derived from acf and the available p wave total attenuation images at 2000 m quantitatively the analysis allows the separation of intrinsic and scattering attenuation on a 2 d plane adding new geophysical constraints to the present knowledge about this volcanic area the final result is a new quantitative image of the past and present tectonic and volcanological state of cfc p wave intrinsic dissipation dominates in an area approximately located under the volcanic centre of solfatara as expected in a region with a large presence of fluids and gas a north south scattering attenuation region is mainly located below the zone of maximum uplift in the 1982 1984 bradiseismic crisis in the sea side of the pozzuoli bay but also extending below mt nuovo this evidence favours the interpretation in terms of a hard but fractured body contoured by strong s wave scatterers corresponding to the caldera rim the region is possibly a section of the residual magma body associated with the 1538 eruption of mt nuovo

an offset in tex86 values between interbedded lithologies implications for sea surface temperature reconstructions abstract the tex 86 tetraether index of tetraethers consisting of 86 carbon atoms sea surface temperature sst proxy is based on the distribution of isoprenoid glycerol dialkyl glycerol tetraether gdgt membrane lipids of pelagic thaumarchaeota that are preserved in marine sediments it is a valuable tool for reconstructing past ssts from sedimentary archives however there are still major uncertainties as to the effects of variables other than temperature on the proxy here we present the first study of gdgt variability across early cretaceous interbedded pelagic and shelf sourced turbiditic sediments from two deep sea drilling project dsdp sites in the western north atlantic the results indicate that a small but consistent offset in tex 86 ratios equivalent to 1 2 c of temperature difference occurs between interbedded lithologies of a similar age the offset can be attributed to spatial differences in sea surface temperatures or thaumarchaeotal populations between the shelf and the open ocean or to secondary diagenetic effects related to oxic degradation of the gdgts of these a difference in either thaumarchaeotal taxa or ecology between those living in the shelf and ocean areas seems most plausible regardless of the root cause of the offset these findings highlight the necessity of careful sample selection prior to tex 86 analysis to ensure robust interpretation of palaeotemperature trends

late paleozoic rotations of corsica and sardinia new evidence from paleomagnetic and k ar studies abstract a detailed paleomagnetic investigation of so called permian volcanics was undertaken in southeastern and northwestern sardinia k ar dating on separate minerals representing 30 sites on corsica and sardinia showed that the first calc alkaline cycle had taken place in westphalo stephanian times and the second alkaline one at the end of the stephanian 246 paleomagnetic specimens from 28 sites of southeastern sardinia and 2 sites from the northwest were demagnetized by alternating field and thermal processes the directions of characteristic magnetizations are d 85 i 6 95 5 for the volcanics of southeastern sardinia and d 126 i 1 for the nurra samples these mean directions differ from those of northwestern corsica and northern sardinia gallura the paleomagnetic results display good grouping for each volcanic complex but exhibit a geographical dispersion of the mean directions this scattering suggests significant motions in late hercynian times

intrinsic and scattering attenuation images of usu volcano japan we present intrinsic and scattering q attenuation images for usu volcano japan by analyzing over 1800 vertical seismograms by fitting the observed envelopes to the diffusion model we obtained intrinsic and scattering attenuation values at three different frequency bands using a back projection method and assuming a gaussian type weighting function we obtained the 2d images of intrinsic and scattering attenuation resolution tests confirm the robustness and reliability of the obtained images we found that scattering attenuation is the dominant process of energy loss in the frequency range analyzed which suggests strong spatial heterogeneity the resultant scattering attenuation images show an increase of attenuation toward the southwest from toya caldera which may correspond to deepening of the basement we also identify an area of low intrinsic and scattering attenuation at the summit of usu volcano which could be associated with old magma intrusions our results demonstrate a strong spatial relation between structural heterogeneities and attenuation processes in volcanic areas and confirm the efficiency of the method which can be used together with conventional imaging techniques

variations in gdgt distributions through the water column in the south east atlantic ocean abstract the tetraether index of 86 carbon atoms tex 86 temperature proxy is widely used in reconstructions of past sea surface temperature most current calibrations are based on surface sediment distributions of the glycerol dialkyl glycerol tetraether lipids gdgts that comprise tex 86 and assume that these gdgts are exported from the upper mixed layer however gdgt export from deeper waters could impact sedimentary gdgt distributions and therefore tex 86 paleothermometry here we examine gdgt distributions in suspended particulate matter spm and underlying sediments collected from the southeast atlantic ocean our results reveal different gdgt distributions specifically the ratio between gdgts bearing 2 vs 3 cyclopentyl moieties 2 3 ratios between surface subsurface 50 200 m and deep water 200 m spm which suggests the occurrence of in situ deep production that is not apparent when considering tex 86 the gdgt distributions in sediments match those of subsurface waters rather than surface waters suggesting that they have not been preferentially derived from the upper mixed layer this is consistent with gdgt abundances being highest in shallow subsurface spm 100 to 200 m it remains unclear what governs the different 2 3 ratios throughout the water column but it is likely related to a combination of temperature and thaumarchaeotal community structure

analysis of multiple scattering at vesuvius volcano italy using data of the tomoves active seismic experiment data from the tomoves active seismic experiment are used to study scattering effects in the shallow heterogeneous structure of vesuvius volcano seismograms from shots located on the volcano itself are characterised by spindle like envelopes small or missing p onsets missing s onsets and long codas seismograms from shots in the surroundings of the volcano on the contrary show clear and impulsive p and s onsets and short codas the different shapes of the envelopes can be explained by strong multiple scattering in the shallow heterogeneous eruptive material of the volcano and single scattering in the surrounding crust the seismograms of shots located on the volcano are modeled using the diffusion model with a diffusivity of d 0 1 km2 s for the frequency range of 2 16 hz assuming the dominance of s waves in the coda and a typical s wave velocity of around 1 5 km s this corresponds to a transport mean free path ltr of only 200 m which is 3 orders of magnitude smaller than for normal earth crust these results show that multiple scattering is an important effect which cannot be neglected in the modeling of seismic wave propagation in volcanic environments

a stochastic view of lower crustal fabric based on evidence from the ivrea zone despite its complicated history the ivrea zone is considered to be a representative surface exposure of extended continental crust we have digitized two standard 1 25 000 geological maps from this area and evaluated their structural statistics because of the subvertical orientation of the ivrea zone these maps can be considered as small scale cross sections through the lower continental crust the autocorrelation functions of the digitized lithologies measured from these maps show a clear self similar or fractal rather than a gaussian or deterministic trend we found that an anisotropic von karman correlation function with an aspect ratio around 4 and a hurst number of 0 3 corresponding to a fractal dimension of 2 7 matches the observed data our results represent an explicit confirmation of previous indirect evidence for the fractal nature of lithospheric heterogeneities and provide the means to construct realistic crustal scale seismic models of ivrea type lower continental crust

merging active and passive data sets in traveltime tomography the case study of campi flegrei caldera southern italy we propose a strategy for merging both active and passive data sets in linearized tomographic inversion we illustrate this in the reconstruction of 3d images of a complex volcanic structure the campi flegrei caldera located in the vicinity of the city of naples southern italy the caldera is occasionally the site of significant unrests characterized by large ground uplifts and seismicity the p and s velocity models of the caldera structure are obtained by a tomographic inversion based on travel times recorded during two distinct experiments the first data set is composed of 606 earthquakes recorded in 1984 and the second set is composed of recordings for 1528 shots produced during the serapis experiment in 2001 the tomographic inversion is performed using an improved method based on an accurate finite difference traveltime computation and a simultaneous inversion of both velocity models and earthquake locations in order to determine the adequate inversion parameters and relative data weighting factors we perform massive synthetic simulations allowing one to merge the two types of data optimally the proper merging provides high resolution velocity models which allow one to reliably retrieve velocity anomalies over a large part of the tomography area the obtained images confirm the presence of a high p velocity ring in the southern part of the bay of pozzuoli and extends its trace inland as compared to previous results this annular anomaly represents the buried trace of the rim of the campi flegrei caldera its shape at 1 5 km depth is in good agreement with the location of hydrothermalized lava inferred by gravimetric data modelling the vp vs model confirms the presence of two characteristic features at about 1 km depth a very high vp vs anomaly is observed below the town of pozzuoli and is interpreted as due to the presence of rocks that contain fluids in the liquid phase a low vp vs body extending at about 3 4 km depth below a large part of the caldera is interpreted as the top of formations that are enriched in gas under supercritical conditions

three component seismogram envelope synthesis in randomly inhomogeneous semi infinite media based on the single scattering approximation abstract we present a method for synthesizing three component seismogram envelopes of local earthquake in a randomly inhomogeneous semi infinite medium the method extends the single scattering model of sato sato h 1984 attenuation and envelope formation of three component seismograms of small local earthquakes in randomly inhomogeneous lithosphere j geophys res 89 1221 1241 by incorporating the effects of a free surface frequency dependent non spherical radiation from a double couple point source and non isotropic scattering including wave type conversion we synthesize seismogram envelopes the root mean square rms amplitude of seismograms at a receiver located on the free surface by dividing an inhomogeneous medium into many small cells and summing the energy of scattered waves from the cells on the isochronal scattering shells of different scattering modes for a given lapse time our main focus is the free surface effect which alters the shape of isochronal scattering shells and the amplitudes of incident waves synthesizing three component seismogram envelopes for different source receiver configurations we find that these effects on seismogram envelopes are not negligible and are pronounced at early s coda p coda envelope shape is not very sensitive to free surface incorporation because of dominant sp scattered waves which come from the source direction

impact of lateral transport on organic proxies in the southern ocean lateral transport of fine grained organic carbon particles can complicate the interpretation of paleoclimate records based on organic proxies here we investigated the effect of lateral transport on newly developed temperature and soil organic matter proxies tex86 and bit index respectively in core md88 769 recovered from the south east indian ridge our results show that tex86 and bit records in comparison to diatom and foraminifera records were representative for more local climate changes while alkenones and n alkanes originated from distant areas by oceanic and atmospheric transport respectively this suggests that tex86 and bit paleoclimate records are primarily influenced by local conditions and less subjected to long distance lateral transport than other organic proxies in the southern ocean

thin skinned tectonics in the northern rhenish massif germany a network of profiles in the hercynian mountain system geo traverse rhenoherzynikum is needed to determine details of the geological structure and find the reasons for tectonic movements outstanding features within the mountain system such as the large fault zone along the southern boundary of the hunsruck1 and the left flank of the rhinegraben have already been investigated by reflection seismology2 3 we describe here a new reflection refraction experiment carried out in 1978 in the most northern part of the rhenish massif across the stavelot venn massif near aachen fig 1 while layers in the lower crust dip to the nnw a strong upper reflector at 3 4 km depth shows a slight dip to the sse and indicates a prominent fault zone near aachen known in belgium as the faille du midi here a comparable and apparently identical reflector was found some 100 and 175 km to the west of our profile we interpreted this reflector as a prominent and well lubricated thrust fault along which a huge horizontal nappe displacement took place during the last stages of the variscan orogeny

compound specific radiocarbon dating of the varved holocene sedimentary record of saanich inlet canada 1 the radiocarbon contents of various biomarkers extracted from the varve counted sediments of saanich inlet canada were determined to assess their applicability for dating purposes calibrated ages obtained from the marine planktonic archaeal biomarker crenarchaeol compared favorably with varve count ages the same conclusion could be drawn for a more general archaeal biomarker gdgt 0 although this biomarker proved to be less reliable due to its less specific origin the results also lend support to earlier indications that marine crenarchaeota use dissolved inorganic carbon dic as their carbon source the average reservoir age offset r of 430 years determined using the crenarchaeol radiocarbon ages varied by 110 years this may be caused by natural variations in ocean atmosphere mixing or upwelling at the ne pacific coast but variability may also be due to an inconsistency in the marine calibration curve when used at sites with high reservoir ages

seismic monitoring and modeling of an active volcano for prediction we describe seismic monitoring and modeling of an active volcano for the purpose of predicting the magma transport process in real time we selected the piton de la fournaise which has been monitored by an observatory since the early 1980s and is active with 28 eruptions from 1980 until august 1992 it erupted on march 9 1998 after an unusually long quiet period the eruption lasted until september 21 1998 before the march eruption we completed the initial construction of a model of a magma system based primarily on long period lp events and coda localization we found that lp events are associated with the lateral movement of magma to the rift zone and not with the vertical movement to the summit we also found that the source of 2 hz lp events is located below that of 1 hz lp events the coda localization is a newly discovered phenomenon that helped to locate a magma body this model was used for interpreting the incoming information from the precursory seismic crisis and the eruption tremor during the 6 months of the eruption the simultaneous monitoring and modeling of an active volcano led us to a quantitative simulation of the eruption process computing excess pressure and flow rate in a system of reservoirs connected by channels

miocene to pliocene development of surface and subsurface temperatures in the benguela current system 1 the initiation of the benguela upwelling has been dated to the late miocene but estimates of its sea surface temperature evolution are not available this study presents data from ocean drilling program odp site 1085 recovered from the southern cape basin samples of the middle miocene to pliocene were analyzed for alkenone based u37k sstuk and glycerol dialkyl glycerol tetraether gdgt based tex86 temptex water temperature proxies in concordance with global cooling during the miocene sstuk and temptex exhibit a decline of about 8 c and 16 c respectively the temperature trends suggest an inflow of cold antarctic waters triggered by antarctic ice sheet expansion and intensification of southern hemisphere southeasterly winds a temperature offset between both proxies developed with the onset of upwelling which can be explained by differences in habitat alkenone producing phytoplankton live in the euphotic zone and record sea surface temperatures while gdgt producing thaumarchaeota are displaced to colder subsurface waters in upwelling influenced areas and record subsurface water temperatures we suggest that variations in subsurface water temperatures were driven by advection of cold antarctic waters and thermocline adjustments that were due to changes in north atlantic deep water formation a decline in surface temperatures an increased offset between temperature proxies and an increase in primary productivity suggest the establishment of the benguela upwelling at 10 ma during the messinian salinity crisis between 7 and 5 ma surface and subsurface temperature estimates became similar likely because of a strong reduction in atlantic overturning circulation while high total organic carbon contents suggest a biogenic bloom in the pliocene the offset between the temperature estimates and the cooling trend was reestablished

sea surface temperature reconstructions over the last 70 kyr off portugal biomarker data and regional modeling this study aims at providing robust temperature reconstructions for a key oceanographic setting in the north atlantic and at understanding the nature of the temperature signal recorded by the two biomarkers u 37 k and tex86 considering season and depth of production to do so high resolution signals of u 37 k and tex86 are determined for the last 70kyr for core md95 2042 located off portugal signals of u 37 k and tex86 present a tight correlation demonstrating a dominant temperature effect u 37 k signals correspond well to the annual mean sea surface temperature sst whereas tex86h derived temperatures are 5 6 degrees c higher which is unrealistically warm for this area unsuitable tex86 global linear calibrations on the iberian margin may suggest a possible occurrence of archaeal communities with specific temperature response to assess the impact of different season or depth of production of the biomarkers on the recorded temperature in the sediment modeled temperature proxies tproxies are introduced in a regional oceanic modeling system and tested for different seasons annual summer winter and depths surface and 0 200m of production for three climate modes present day pd last glacial maximum lgm and heinrich stadials hs similar temperature amplitudes between climate modes are found at md95 2042 core site for observations for both biomarkers and for modeled annual surface production tproxy 5 5 7 degrees c for t pd lgm and 3 4 degrees c for t lgm hs therefore we propose a new tex86h regional calibration to reconstruct present and past annual mean ssts on the iberian margin

the influence of oxic degradation on the sedimentary biomarker record ii evidence from arabian sea sediments abstract biomarker accumulation rates in nine different time slices in three cores on and at the foot of a submarine high in the northern arabian sea the murray ridge were measured to investigate the influence of oxygen exposure time on the preservation of biomarker signals in the sedimentary record all three sites experienced the same history of surface water productivity and sediment supply but had different bottom water redox conditions due to their different positions in just below well below relative to the present location of the intense oxygen minimum zone omz past variations in the intensity and position of the omz known from a wide variety of proxies toc content distribution and abundance of planktonic and benthic foraminifera and pteropods trace metals and 15 n enabled specific biomarker i e n alkanes steroids alkenones alkyldiols c 26 fatty acid loliolide biphytane diols and archaeal tetraether lipids accumulation rates at contrasting oxygen exposure times to be compared the results indicate that these accumulation rates can vary by more than an order of magnitude for marine biomarkers in addition there are significant differences in the degree of oxic degradation of different types of biomarkers terrestrial n alkanes are much more resistant than alkenones and n alkyl diols which are more refractory than steroids and biphytane diols these differences in degree of oxic degradation indicate that biomarker distributions will change on increasing exposure to oxygen these findings have a significant impact on the application of biomarkers to sedimentary settings in which oxygen exposure time is likely to change significantly

laterally heterogeneous scattering explains lg blockage in the pyrenees 1 we present an algorithm to simulate the propagation of seismic energy in a model that contains both deterministic structure and statistically described small scale heterogeneities with this algorithm we study the propagation of seismic waves through the pyrenees using a series of seismograms the variations of the attenuation properties of the crust along the pyrenean axis are illustrated the western pyrenees exhibit strong attenuation of crustal phases a phenomenon known as lg blockage previous studies demonstrated that the large scale velocity structure of the western pyrenees cannot explain the strong lateral variations of attenuation along the pyrenean range in this paper we present a model that is able to explain the principal observations we propose that the lg blockage is caused by a perturbed region of the crust with scattering and anelastic properties that differ markedly from the surrounding crust numerical simulations of the elastic radiative transfer equation in a layered medium show that it is possible to model the observed lg blockage with increased scattering in the perturbed body in order to explore the relative importance of scattering and attenuation we performed an inversion of the data using a genetic algorithm our study reveals that stronger intrinsic attenuation in the perturbed body improves the fit to the data but that intrinsic attenuation alone cannot explain the observations our work puts forward the role of multiple scattering in the attenuation mechanism of crustal phases

distribution and export of isoprenoid tetraether lipids in suspended particulate matter from the water column of the western atlantic ocean abstract the tex86 paleotemperature proxy is based on the distribution of archaeal glycerol dibiphytanyl glycerol tetraether gdgt lipids preserved in marine sediments yet both the influence of different physiological factors on the structural distribution of gdgts and the mechanism s by which gdgts is are exported to marine sediments remain s unresolved we investigated the abundance and structural distribution of gdgts in the south west and equatorial atlantic ocean in four water column profiles spanning 48 degrees of latitude the depth distribution was consistent with production by ammonia oxidizing thaumarchaeota maximum gdgt concentration occurred at the base of the no2 maximum core gdgts dominated the structural distribution in surface waters above the no2 maximum and intact polar gdgts potentially indicating live cells were more abundant below the no2 maximum between 0 and1000 m 98 of the integrated gdgt inventory was present in waters at and below the no2 maximum depth profiles of tex86 temperature values displayed local minima at the no2 maximum while the ratio of gdgt 2 gdgt 3 increased with depth a model based on the results predicts an average depth of origin for gdgts exported to sediments between ca 80 250 m in the model exported tex86 values are remarkably insensitive to change in the average depth of origin of gdgts however tex86 values exported from the water column appear to reflect euphotic zone productivity possibly due to the correlative intensity of organic matter remineralization providing substrates for ammonia oxidation predicting the influence of these regional controls on sedimentary tex86 records requires a better understanding of the interaction between gdgt production particle dynamics and the depth of origin for exported organic matter

seismicity associated with the 2004 2006 renewed ground uplift at campi flegrei caldera italy abstract following the significant ground uplift 1 8 m of the 1982 1984 bradyseismic crisis the recent history of campi flegrei volcanic complex italy has been dominated by a subsidence phase recent geodetic data demonstrate that the subsidence has terminated and that positive ground deformation renewed in november 2004 at a low but accelerating rate leading to about 4 cm of uplift by the end of october 2006 as in previous episodes ground uplift has been accompanied by swarms of micro earthquakes m 1 4 in three distinct episodes october 2005 october 2006 and december 2006 hypocenters of these earthquakes are mainly located beneath the solfatara volcano at depths ranging between 0 5 and 4 km inversion of s wave spectra indicates source radius and stress drop on the order of 30 60 m and 104 9 105 pa respectively fault plane solutions indicate predominantly normal mechanisms accompanying the october 2006 swarm we detected intense long period lp activity for about 1 week these signals consist of weak monochromatic oscillations whose spectra exhibit a main peak at frequency 0 8 hz this peak is common to all the stations of the network and not present in the noise spectra suggesting that it is a source effect about 75 of the detected lps cluster into three groups of mutually similar events adjustment of waveforms using cross correlation allows for precise alignment and stacking which enhances signal onsets and permits accurate absolute arrival picks and thus better absolute as well as relative locations locations associated with the three different clusters are very similar and appear to delineate the se rim of the solfatara volcano at a depth of about 500 m the most likely source process for the lp events involves the resonance of a fluid filled buried cavity quality factors of the resonator cluster in a narrow interval around 4 which is consistent with the vibration of a buried cavity filled with a water vapour mixture at poor gas volume fractions we propose a conceptual model to interpret the temporal and spatial patterns of the observed seismicity

three dimensional kernel based coda attenuation imaging of caldera structures controlling the 1982 84 campi flegrei unrest abstract coda wave attenuation imaging has risen as a state of the art technique to depict volcanic structures using their dispersion effects the 1982 84 seismic and deformation unrest at campi flegrei caldera italy is a unique example of non eruptive volcanic activity in a structured caldera here we propose the first application of 3d coda attenuation kernels to image caldera structures at multiple frequencies during unrest using sensitivity kernels is necessary to assess the effective resolution of coda imaging in highly heterogeneous volcanoes the technique relies on the solution of paasschens equations in the framework of radiative transfer theory the results map coda attenuation in the 3d space without need of pre existent velocity models the resolution and stability of the inversion solutions were examined by changing the damping parameters and outputting the corresponding images inverting for different node spacings and performing checkerboard tests these tests show that the resolution of the multiple scattering model is much lower than that provided by a standard isotropic scattering and or single scattering technique the best resolution in our model is obtained between depths of 1 km and 3 km in the centre of the model between pozzuoli town and solfatara crater the results are discussed at a frequency of 3 hz due to both longer coda durations and broader kernel illumination in this frequency range coda based 3d imaging had so far failed to provide stable results the interpretation is performed based on the extensive geological and geophysical knowledge of the caldera high attenuation anomalies below solfatara and monte nuovo mark areas either saturated with water or enriched in molten rocks feeding the respective fumarole fields the flattening and horizontal elongation of these anomalies below 2 km depth is a manifestation of the blocking and spreading around of the rising hot magmatic fluids below a previously inferred high velocity low attenuation and highly deforming caprock this caprock is not uniform likely due to the remnants of erupted structure a sw to ne trending low attenuation and high velocity anomaly deeps down to 3 km under pozzuoli we infer that the high seismicity in the region is a consequence of the stress sustained by the caprock from a 4 km deep deformation source in 1983 84 on top of this source high coda attenuation corresponds to high vp vs ratios and high direct wave attenuation the region s characteristics are likely due to the accumulation of magmatic fluids above a magmatic sill

a review of molecular organic proxies for examining modern and ancient lacustrine environments molecular organic geochemical proxies are increasingly being utilized to reconstruct past environmental conditions as new tools continue to be discovered and developed to date organic geochemical proxies have been developed mainly for use in marine systems and are widely used in paleoceanography in contrast organic proxies have been less commonly used on lacustrine sedimentary records one reason for this is that the wide range in the physical and chemical properties of lakes complicates application of some organic geochemical proxies in lacustrine settings furthermore in comparison to marine studies presently only a small number of studies have conducted or are currently conducting fundamental research aimed at developing organic geochemical proxies for use in lacustrine settings despite this an increasing number of paleo limnological studies are currently applying organic geochemical techniques to examine present and past environmental conditions in this manuscript we review the use of a number of commonly utilized organic geochemical and isotopic proxies and discuss their potential for environmental reconstruction in quaternary lacustrine deposits

an experimental field study to test the stability of lipids used for the tex86 and uk 37 palaeothermometers abstract we report a one year field experiment to study sedimentary degradation of isoprenoid glycerol dialkyl glycerol tetraethers gdgts and long chain alkenones lipids used for the tex86 and u 37 k sea surface temperature sst proxies respectively homogenised surface sediments from the namibian upwelling region were set out on moorings in oxic oder bay and arkona bay baltic sea and sub oxic to anoxic gottland basin baltic sea waters and in oxic atlantic waters off cape blanc for one year to assess the influence of oxygen exposure on gdgts and alkenones no selective degradation effect on both tex86 and u 37 k proxies was evident under anoxic and sub oxic conditions under oxic conditions gdgt concentrations and the tex86 did not significantly change as well however selective degradation of alkenones occurred at all oxic sites resulting in a small but significant increase of the u 37 k index by up to 0 06 units corresponding to a temperature increase of up to 1 8 c our results demonstrate that selective alkenone degradation is a relatively fast process and complement earlier evidence for selective degradation of alkenones in the laboratory water column and sediments in contrast our results suggest that the tex86 is relatively resistant to selective oxic degradation at least on relatively short years time scales

gdgt and alkenone flux in the northern gulf of mexico implications for the tex86 and uk 37 paleothermometers the tex86 and u37k molecular biomarker proxies have been broadly applied in downcore marine sediments to reconstruct past sea surface temperature sst although both tex86 and u37k have been interpreted as proxies for mean annual sst throughout the global ocean regional studies of glycerol dibiphytanyl glycerol tetraethers gdgts and alkenones in sinking particles are required to understand the influence of seasonality depth distribution and diagenesis on downcore variability we measure gdgt and alkenone flux as well as the tex86 and u37k indices in a 4 year sediment trap time series 2010 2014 in the northern gulf of mexico ngom and compare these data with core top sediments at the same location gdgt and alkenone fluxes do not show a consistent seasonal cycle however the largest flux peaks for both occurs in winter u37k covaries with sst over the 4 year sampling interval but the u37k sst relationship in this data set implies a smaller slope or nonlinearity at high temperatures when compared with existing calibrations furthermore the flux weighted u37k value from sinking particles is significantly lower than that of underlying core top sediments suggesting preferential diagenetic loss of the tri unsaturated alkenone in sediments tex86 does not covary with sst suggesting production in the subsurface upper water column the flux weighted mean tex86 matches that of core top sediments confirming that tex86 in the ngom reflects local planktonic production rather than allochthonous or in situ sedimentary production we explore potential sources of uncertainty in both proxies in the ngom but demonstrate that they show nearly identical trends in twentieth century sst despite these factors

palaeomagnetism of the ibero armorican arc and the hercynian orogeny in western europe van der voo1 has pointed out that further advances in the understanding of the hercynian orogeny require palaeomagnetic data from well studied orogenic areas we report here palaeomagnetic results of palaeozoic rocks taken in brittany portugal and spain in the ibero armorican arc iaa a large geological feature considered to be a key area for the hercynian orogeny in western europe they show evidence that the iaa formed in two stages extending results obtained in spain by ries et al 2 giving precise constraints for the former shape of the arc we can use pre hercynian palaeomagnetic directions found in spain and portugal to follow its evolution during palaeozoic times this megastructure linking brittany to iberia squeezed between gondwana and the northern continents during the carboniferous did break away from the former block during ordovician times

high and low latitude climate control on the position of the southern peru chile current during the holocene 1 we reconstructed changes of temperature salinity and productivity within the southern peru chile current during the last 8000 years from a high resolution sediment core recovered at 41 s using alkenones isotope ratios of planktic foraminifera biogenic opal and organic carbon paleotemperatures and paleosalinities reached maximum values at 5500 years ago and thereafter declined to modern values whereas paleoproductivity continuously increased throughout the last 8000 years we ascribe these long term holocene trends primarily to latitudinal shifts of the antarctic circumpolar current acc the concurrence with shifts in the position of the southern westerlies points to a common response of atmospheric and oceanographic circulation patterns off southern chile millennial to centennial scale fluctuations of paleotemperatures and paleosalinities on the other hand lag displacements in the position of the southern westerlies but reveal a significant correlation to short term temperature changes in antarctica indicating a high latitude control of the acc at these timescales

large changes in seasonal sea ice distribution and productivity in the sea of okhotsk during the deglaciations changes in the surface environment of the central sea of okhotsk were reconstructed using tex86 paleothermometry facilitated by the bit index in order to investigate paleoenvironmental changes during the glacial interglacial cycles the core top tex86 derived temperature is the same as the present day summer sea surface temperature sst suggesting that tex86 records seasonal rather than annually averaged ssts in this region the tex86 record reveals 3 c lower summer sst during glacial maxima than during interglacial periods and significant warming during the deglaciations 15 10 ka and 136 130 ka this is consistent with previous inferences of more expanded and persistent seasonal sea ice during the glacial periods than the present day and its substantial retreat during the deglaciation timing of the deglacial warming also coincided with a distinct increase in coccolithophorid productivity suggesting a causal relationship between sea surface warming and coccolithophorid blooms during the deglaciations the relationship could reflect an increase in the supply of fresh and warm water from the amur river during deglaciation which significantly impacted hydrology by facilitating sea surface stratification which in turn promoted production of coccolithophids

broad band power law spectra of well log data in japan summary for the purpose of revealing the statistical characteristics of p wave velocity s wave velocity and density in the uppermost part of the crust we analysed well log data obtained from five deep wells in different tectonic regions in japan three wells through the mainly sedimentary rocks in the kanto plain and two wells in the kuju volcano group in kyushu island in the kanto plain the power spectral density of fractional fluctuation of p wave velocity and that of density are proportional to a power of the spatial wavelength from a few metres to 100 m where the power index slope of the power spectral density at double logarithmic scale is 1 1 1 3 at the kuju volcano group that of p and s wave velocity and density also obey a power law with a power index of 1 3 1 6 for wavelengths from a few metres to few hundred metres correcting the effect of the moving box car observation window which corresponds to the separation of two receivers of the logging tool we find that the power law characteristics hold for wavelengths down to a few tens of centimetres the 1 d sections of the elastic inhomogeneities follow a kind of band limited self affine random process comparing the power spectral densities we find smaller values of the power index in stable areas and larger values in tectonically active areas the difference in the power index arises from long wavelength components

comparison of eastern tropical pacific tex 86 and globigerinoides ruber mg ca derived sea surface temperatures insights from the holocene and last glacial maximum abstract the use of the tex 86 temperature proxy has thus far come to differing results as to whether tex 86 temperatures are representative of surface or subsurface conditions in addition although tex 86 temperatures might reflect sea surface temperatures based on core top holocene values this relationship might not hold further back in time here we investigate the tex 86 temperature proxy by comparing tex 86 temperatures to mg ca temperatures of multiple species of planktonic foraminifera for two sites in the eastern tropical pacific on the cocos and carnegie ridges across the holocene and last glacial maximum core top and holocene tex 86 h temperatures at both study regions agree well within error with the mg ca temperatures of globigerinoides ruber a surface dwelling planktonic foraminifera however during the last glacial maximum tex 86 h temperatures are more representative of upper thermocline temperatures and are offset from g ruber mg ca temperatures by 5 8 c and 2 9 c on the cocos ridge and carnegie ridge respectively this offset between proxies cannot be reconciled by using different tex 86 temperature calibrations and instead we suggest that the offset is due to a deeper export depth of gdgts at the lgm we also compare the degree of glacial cooling at both sites based on both temperature proxies and find that tex 86 h temperatures greatly overestimate glacial cooling especially on the cocos ridge this study has important implications for applying the tex 86 paleothermometer in the eastern tropical pacific

low latitude climate control on sea surface temperatures recorded in the southern okinawa trough during the last 13 3 kyr abstract paleotemperature records were reconstructed for the past 13 3 kyr using the alkenone unsaturation index uk 37 and the tetraether index of 86 carbon atoms tex86 proxies measured in sediment core oki 151 which was collected in the southern okinawa trough the uk 37 and tex86 derived temperatures for the top sample are close to the modern mean annual sea surface temperature sst changes in ssts in the southern okinawa trough were primarily controlled by the western tropical pacific ocean low latitude winter insolation and sea level rise unlike previous studies we found that the high latitude north atlantic played no significant role in the sst variations in this area moreover ssts in the southern okinawa trough decoupled from the east asian summer monsoon system in the last 13 3 kyr the uk 37 and tex86 based ssts dropped significantly at 7 6 6 9 kyr bp centered on 7 3 kyr bp these findings suggest that the cold event at 7 3 kyr bp was widely recorded in the okinawa trough however the tex86 based ssts dropped approximately 14 c during this period for an unknown reason

distribution of intact and core tetraether lipids in water column profiles of suspended particulate matter off cape blanc nw africa in the reconstruction of sea surface temperature sst from sedimentary archives secondary sources lateral transport and selective preservation are considered to be mainly negligible in terms of influencing the primary signal this is also true for the archaeal glycerol dialkyl glycerol tetraethers gdgts that form the basis for the tex86 sst proxy our samples represent four years variability on a transect off cape blanc nw africa we studied the subsurface production vertical and lateral transport of intact polar lipids and core gdgts in the water column at high vertical resolution on the basis of suspended particulate matter spm samples from the photic zone the subsurface oxygen minimum zone omz nepheloid layers nl and the water column between these furthermore we compared the water column spm gdgt composition with that in underlying surface sediments this is the first study that reports tex86 values from the precursor intact polar lipids ipls associated with specific head groups ipl specific tex86 we show a clear deviation from the sea surface gdgt composition in the omz between 300 and 600 m since neither lateral transport nor selective degradation provides a satisfactory explanation for the observed tex derived temperature profiles with a bias towards higher temperatures for both core and ipl specific tex86 values we suggest that subsurface in situ production of archaea with a distinct relationship between lipid biosynthesis and temperature is the responsible mechanism however in the nw african upwelling system the gdgt contribution of the omz to the surface sediments does not seem to affect the sedimentary tex86 as it shows no bias and still reflects the signal of the surface waters between 0 and 60 m

a volcanic front as a boundary of seismic attenuation structures in northeastern honshu japan we investigated the spatial distribution of s coda wave energy in northeastern honshu japan where a volcanic front runs from north to south seismograms of a local event with a magnitude of 6 4 recorded by the hi net were analyzed in this study the mean square amplitudes of coda waves at 82 seismic stations were calculated for bands with frequencies of 2 4 4 8 8 16 and 16 32 hz from these measurements a clear spatial variation of coda wave energy was observed across the volcanic front from east forearc to west backarc the coda wave energy is uniformly distributed in the forearc whereas an exponential decrease with horizontal offset from the volcanic front is found in the backarc the decay rate increases with increasing frequency we propose a diffusion absorption model to give a physical insight into the observed regional variation in coda wave energy this model explains the observed characteristics successfully and predicts that the exponential variation of coda wave energy in the backarc is a function of the diffusivity and the absorption coefficient the magnitude of the intrinsic attenuation factor in the backarc is estimated at about q i 1 0 02 at a frequency of 10 hz by assuming a value of 0 01 km 1 for the scattering coefficient this intrinsic attenuation factor is about twice as large as those reported from previous studies on the forearc

seismic energy envelopes in volcanic media in need of boundary conditions this work was carried out under the hpc europa2 project project number 228398 with the support of the european commission capacities area research infrastructures initiative we thank the whole staff at epcc edinburgh parallel computing centre in edinburgh and particularly dr adam carter for their help in both developing and parallelizing the code the challenging comments and suggestions of the editor and two anonymous reviewers helped both in focusing the aim and in overcoming the strong limits of a previous version of the paper

seismic attenuation imaging of campi flegrei evidence of gas reservoirs hydrothermal basins and feeding systems 1 passive high resolution attenuation tomography is used here to image the geological structure in the first upper 4 km of the shallow crust beneath the campi flegrei caldera southern italy the inverse q was estimated for each source receiver path using the coda normalization method s waves and the slope decay method p waves and s waves inversion was performed using a multi resolution method which ensures a minimum cell size resolution of 500 m the study of the resolution matrix as well as the synthetic tests guarantee an optimal reproduction of the input anomalies in the center of the caldera between 0 and 3 5 km in depth high attenuation vertical structures are connected at the surface with the main volcanological features e g the solfatara and mofete fumarole fields and depict vertical q contrast imaging important geological structures such as the la starza fault these high attenuation volumes extend between the surface and a depth of about 3 km where a hard rock layer is imaged by the sharp contrast of the quality factors the retrieved image of the campi flegrei has been jointly interpreted taking into account evidence from seismological geological volcanological and geochemical investigations this analysis has allowed an unprecedented view of the feeding systems in this area and in particular it recognizes the vertically extending high attenuation structures that correspond to gas or fluid reservoirs beneath pozzuoli solfatara solfatara mofete mt nuovo and agnano this high attenuation system is possibly connected with the magma sill revealed at about 7 km in depth by passive travel time tomography

scattering behaviour at merapi volcano java revealed from an active seismic experiment summary the seismic structure of the stratovolcano merapi java indonesia was studied using an active seismic experiment three 3 km long seismic profiles each consisting of up to 30 three component seismometers with an interstation distance of 100 m were built up in an altitude range between 1000 and 2000 m above sea level the detailed study of the seismic properties of the propagation media in active volcanic regions is important to understand the natural seismic signals used for eruption forecasting the seismic experiment at merapi therefore concentrates on the heterogeneous structure within a radius of 5 km from the active dome where the sources of most of the natural volcanic seismic events are located the cone of merapi volcano consists of different materials changing on a small scale due to the layering of eruptive material additionally the topography of the erosion valleys leads to an irregular deposition which cannot be described by a simple 1 d layering these inhomogeneities have a strong influence on seismic signals the direct p and s waves are attenuated quickly and show only small amplitudes on seismograms the energy lost from the direct waves however is not changed into heat but scattered and can be observed as seismic coda following the direct waves the observed seismograms show a spindle like amplitude increase after the direct p phase this shape of the envelope can be explained by the diffusion model according to this model there are so many strong inhomogeneities that the direct wave can be neglected and all energy is concentrated in multiple scattered waves besides the envelope the coherence and polarization properties of the wavefield also indicate strong scattering only the first onset shows coherence over a station spacing of 100 m whereas the late phases carrying the major part of the energy are mainly incoherent the horizontal components of the seismograms have larger amplitudes than the vertical component but within the horizontal plane the polarization is almost arbitrary corresponding to waves arriving from scatterers located arbitrarily in space as a result of the inversion using the diffusion model we obtain values of the s wave scattering attenuation coefficient gs and the s wave intrinsic absorption coefficient gi in the frequency range of 4 20 hz used in this study the scattering attenuation is at least one order of magnitude larger than the intrinsic absorption gs gi the mean free path of s waves is as low as 100 m gs1 100 m the scattering coefficient is independent of frequency gsyf 0 0 whereas the coefficient of intrinsic attenuation increases with increasing frequency giyf 1 6 the natural seismic signals at merapi volcano show similar characteristics to the artificial shots the first onsets have only small amplitudes and the energy maximum arrives delayed compared to the direct waves therefore these signals appear to be strongly affected by multiple scattering also

a study of the alkenone tex86 and planktonic foraminifera in the benguela upwelling system implications for past sea surface temperature estimates suspended particulate matter from seawater and core top sediments were collected during 2003 meteor cruise m57 1 in january february from the continental margin off western south africa for analysis of alkenones glycerol dibiphytanyl glycerol tetraether gdgt lipids and planktonic foraminifera alkenone analysis of suspended particulates in seawater and core top sediments indicates that u37k temperatures were representative of annual mean sea surface temperature in contrast gdgt analysis suggests that tex86 temperatures are cold biased due to upward transports of gdgts produced below the mixed layer the analysis of plankton tow samples revealed that the 18o of globorotalia inflata in core top sediments could be biased toward lower temperatures due to subsurface calcification accordingly our study shows that each paleotemperature proxy may record different temperature signals in the benguela upwelling system emphasizing the general need to constrain potential biases in each proxy for better interpreting paleoclimate records

radiative transfer and diffusion of waves in a layered medium new insight into coda q summary this paper is devoted to the study of the seismic coda in inhomogeneous media exhibiting a discontinuity of physical properties at a given depth we focus on the problem of a layer overlying a half space and analyse the precise effect of a contrast of wave velocities and or scattering strengths between them in order to model s codawave envelopes we solve the radiative transfer equation by the monte carlo method thereby neglecting the polarization i e the acoustic approximation we pay special attention to the transition towards the diffusion regime under the assumption of an almost isotropic intensity field a diffusion equation can be derived from the radiative transfer equation and we accurately determine the boundary conditions associated with our models analytical solutions of the diffusion equation have been obtained and systematically compared to the numerical solutions of the radiative transfer equation we identify the domain of validity of the diffusion approximation which provides a simple analytical form for the decay in the late coda we apply our theoretical investigations to the continental lithosphere if the scattering strengths of the mantle and the crust are assumed to be of the same order a velocity contrast at the moho will according to our theory amplify the coda signal since part of the energy is trapped in the crust an amplification factor is defined and given explicitly as a function of the reflection coefficients and the velocity contrast at the moho the shape of the long time decay is of the algebraic form f 3 2 like that of a uniform half space on the other hand if the scattering strength of the mantle is small with respect to that of the crust the decay in the diffusive regime is predicted to be of the form r i exp 2nft qa where q is a function of the reflection coefficients at the moho the mean free path of waves in the crust and frequencyf the coefficient q quantifies the rate at which the partially trapped energy leaks from the crust into the mantle this formula has the same form as that proposed by aki chouet 1975 to fit coda observations which has since been widely used to deduce the qc parameter with realistic model parameters we find that q roughly equals the parameter qc deduced from observations this shows that the effect of partial trapping of energy in the crust may be significant consequently seismic albedos of the crust may have been underestimated in previous studies in our theory the energy decay of seismic coda waves is determined by the layered structure of the earth that is a highly heterogeneous crust overlying a rather homogeneous mantle such structure is confirmed by geological and geochemical studies

scattering images from autocorrelation functions of p wave seismic velocity images the case of tenerife island canary islands spain we present a p wave scattering image of the volcanic structures under tenerife island using the autocorrelation functions of p wave vertical velocity fluctuations we have applied a cluster analysis to total quality factor attenuation q t 1 and scattering quality factor attenuation q psc 1 images to interpret the structures in terms of intrinsic and scattering attenuation variations on a 2d plane corresponding to a depth of 2000 m and check the robustness of the scattering imaging the results show that scattering patterns are similar to total attenuation patterns in the south of the island there are two main areas where patterns differ at canadas teide pico viejo complex high total attenuation and average to low scattering values are observed we interpret the difference as induced by intrinsic attenuation in the santiago ridge zone srz region high scattering values correspond to average total attenuation in our interpretation the anomaly is induced by an extended scatterer geometrically related to the surficial traces of garachico and el chinyero historical eruptions and the area of highest seismic activity during the 2004 2008 seismic crises

a study of the tex86 paleothermometer in the water column and sediments of the santa barbara basin california 1 particulate organic matter collected during a 2 year period as part of an ongoing sediment trap study and a high resolution sediment record from 1850 to 1987 a d from the santa barbara basin were analyzed for tex86 a temperature proxy based on marine crenarchaeotal membrane lipids highest fluxes of crenarchaeotal lipids in the water column were found in may june 1996 and from october 1996 to january 1997 and in general showed a good correlation with mass fluxes tex86 reconstructed temperatures from the sediment trap series ranged from 8 to 11 c and were usually substantially lower than sea surface temperatures sst indicating that unlike in previous studies the tex86 corresponds to subsurface temperatures likely between 100 and 150 m tex86 temperature variations observed in trap samples were not coupled to changes in sst or deep water temperatures and only to some degree with crenarchaeotal lipid fluxes this suggests that a complex combination of different depth origins and seasonal growth periods of crenarchaeota contributed to the variations in tex86 signal during the annual cycle tex86 temperatures in the two sediment cores studied 8 13 c were also substantially lower than those of instrumental sst records 14 17 5 c confirming that tex86 records a subsurface temperature signal in the santa barbara basin this result highlights the importance of performing calibration studies using sediment traps and core tops before applying the tex86 temperature proxy in a given study area

hydrographic variability in the northern south china sea over the past 45 000 years new insights based on temperature reconstructions by uk 37 and texh86 proxies from a marine sediment core md972146 abstract millennial scale climate variability was persistent feature for greenland ice core and north atlantic marine records during the marine isotope stage mis 3 studying high quality climatic archives outside of the greenland and north atlantic with precise constraint of absolute dating and high resolution sampling is a prerequisite to understand how the millennial scale changes well expressed in north hemisphere nh high latitudes had been propagated out to the other regions here we generated the surface and subsurface hydrography u k 37 and tex h 86 temperatures and terrestrial material input n alkanes records with precise ams 14 c dated control for the 45 ka from a core md972146 retrieved from the northern south china sea scs then we compared our records to the oxygen isotope record from a greenland ngrip ice core and the mean grain size record from a loess sequence at gulang china we found that the millennial scale oscillations of hydrolography and terrestrial material inputs records during the time since the last deglaciation and of 33 45 ka share similar patterns in timing and amplitude of the nh high latitude climate however we found that a non nh pattern of millennial scale oscillations for the late mis 3 20 33 ka of our hydrography and terrestrial material inputs records our studies imply that the changes of obliquity also may be important in determining the timing and amplitude of millennial scale east asian monsoon eam variability expressed in the northern scs hydrography and terrestrial material inputs

monte carlo simulation of seismogram envelopes in scattering media the analysis of the seismogram coda envelopes of local and regional earthquakes is one of the most effective strategies for investigating the heterogeneous lithospheric structure characterized by the seismic scattering and attenuation in order to synthesize the coda envelope we introduce a numerical scheme called the direct simulation monte carlo method which has been used in the field of the kinetic theory of gases because of the simplicity of the algorithm the method has several advantages over previous methods in terms of the flexibility of the numerical calculation to incorporate various factors required to construct realistic seismogram envelopes on the basis of coda envelope simulations including multiple scattering we show that an increase of seismic velocity with depth severely affects the shape of the coda envelope the effects of ray bending due to the velocity increase at the moho and the reflection at the free surface are clearly found in the synthesized envelope for a shallow earthquake our simulation demonstrates that the amplitude of the envelope is magnified by stagnation of seismic energy at shallow depths due to the positive velocity gradient with depth because of this effect for an a priori assumption of a homogeneous velocity model the measurement of the scattering coefficient by conventional methods may be overestimated

asynchronous alkenone and foraminifera records from the benguela upwelling system abstract radiocarbon stratigraphy is an essential tool for high resolution paleoceanographic studies age models based on radiocarbon ages of foraminifera are commonly applied to a wide range of geochemical studies including the investigation of temporal leads and lags the critical assumption is that temporal coupling between foraminifera and other sediment constituents including specific molecular organic compounds biomarkers of marine phytoplankton e g alkenones is maintained in the sediments to test this critical assumption in the benguela upwelling area we have determined radiocarbon ages of total c37 c39 alkenones in 20 samples from two gravity cores and three multicorer cores the cores were retrieved from the continental shelf and slope off namibia and samples were taken from holocene deglacial and last glacial maximum core sections the alkenone radiocarbon ages were compared to those of planktic foraminifera total organic carbon fatty acids and fine grained carbonates from the same samples interestingly the ages of alkenones were 1000 to 4500 yr older than those of foraminifera in all samples such age differences may be the result of different processes bioturbation associated with grain size effects lateral advection of recycled material and redeposition of sediment on upper continental slopes due to currents or tidal movement are examples for such processes based on the results of this study the age offsets between foraminifera and alkenones in sediments from the upper continental slope off namibia most probably do not result from particle selective bioturbation processes resuspension of organic particles in response to tidal movement of bottom waters with velocities up to 25 cm s recorded near the core sites is the more likely explanation our results imply that age control established using radiocarbon measurements of foraminifera may be inadequate for the interpretation of alkenone based proxy data observed temporal leads and lags between foraminifera based data and data derived from alkenone measurements may therefore be secondary signals i e the result of processes associated with particle settling and biological activity

source parameters and three dimensional attenuation structure from the inversion of microearthquake pulse width data qp imaging and inferences on the thermal state of the campi flegrei caldera southern italy the three dimensional p wave attenuation structure of the campi flegrei caldera and the estimate of source parameters for 87 local microearthquakes is obtained by the nonlinear inversion of pulse width and rise time measurements by using the method described by zollo and de lorenzo this issue source radii represent the better resolved parameters with values ranging from 70 m to 230 m the dip and strike angles defining fault orientations are usually affected by larger uncertainties and are well constrained only for 11 events the dip fault is usually confined in the range 30 60 with an average uncertainty of 12 the fault strikes mainly range between 60 and 60 and seem to define preferential directions oriented radially from the symmetry axis of the ground deformation stress drop estimates indicate rather low values 0 01 1 mpa which suggest low strength properties of the incoherent and brittle materials filling the caldera primarily yellow tuffs the three dimensional qp images obtained from the inversion of p pulse durations show two significant low qp anomalies between 0 and 1 km of depth in the north eastern sector and at 2 3 km of depth in the central eastern sector of the caldera the high degree of spatial correlation of the low qp zone and low vs as inferred by aster and meyer 1988 at 0 1 km in depth and other geophysical and geochemical observations suggest that this anomaly can be related to the presence of densely fractured porous and fluid filled rocks in the ne sector of the caldera the deeper low qp anomaly is interpreted as being related to a dominant thermal effect we used the surface and deep borehole temperature measurements available in the area to obtain a local calibration curve to convert qp in temperature at campi flegrei the retrieved t qp map shows a high thermal deep disturbance 450 500 c at depths between 2 and 3 km in the eastern sector of the caldera where the most recent eruptive activity is concentrated the present day temperature field retrieved by qp images has been interpreted by using a three dimensional thermal conduction model assuming an extended heat source initial temperature of 800 c located underneath the attenuation anomalous region the results indicate that the qp inferred temperature field can be related to the heat conduction effect of one or more molten bodies whose top should be at about 4 km depth consistent with recent seismic estimates of the magma chamber top at campi flegrei ferrucci et al 1992 this study suggests that the present thermal state and rock rheology of the inner caldera could be controlled by the cooling of molten bodies that originally intruded at depths of 1 4 1 6 km during one or more recent time of 10 kyr eruptive events

mantle and crustal granites genetic classification of orogenic granites and the nature of their enclaves abstract the nature of enclaves must be taken into account in a genetic classification of granites granites containing only restites are different from those also containing basic magmatic enclaves microgranular enclaves if the former are of crustal origin the latter certainly include a mantle component rather than a distinction between s type granites of sedimentary origin and i type granites of igneous origin a distinction is made between c type granites crustal and m type granites mantle or mixed i e crustal mantle the c type granites can be subdivided into cs type anatexis of sedimentary rocks and ci type granites anatexis of igneous rocks in the french massif central the variscan granites belong to these different varieties leucogranites are typical c type granites whereas granodiorites and monzogranites are m type granites including various amounts of mantle component

palaeomagnetic investigations in the hercynian mountain belt of central europe abstract the palaeomagnetism of sediments and volcanics of middle devonian to early carboniferous age has been studied in the hercynian realm of the vosges harz and franconian forest france and germany after appropriate cleaning characteristic directions of natural remanent magnetization nrm have been determined which are considered to be of pretectonic origin according to rock magnetic and structural geological evidence a mean palaeopole for the devonian rocks in the areas investigated was determined at 29 7 n and 9 0 e the site latitude derived from the devonian rocks agrees very well with that observed in great britain and britanny the significant difference in longitude between our devonian poles and the other european data may be due to an anticlockwise rotation of central europe with respect to the northern hercynian foreland the carboniferous rocks yield a mean palaeopole at 41 7 n and 340 4 e matching the carboniferous part of the european polar wander path a fold test within carboniferous greywackes from the harz mountains proves a pre folding origin of the nrm of these rocks however this stable magnetization direction indicates local or regional tectonic displacement our results do not support any major latitudinal motions of continental segments in central europe during the hercynian orogeny the palaeozoic palaeomagnetic data from the vosges franconian forest harz britanny and central massif can be used to interpret the hercynides in terms of a large scale shear belt

absorption and scattering 2 d volcano images from numerically calculated space weighting functions acknowledgments yosuke aoki and an anonymous reviewer greatly improved the quality of the paper all calculations were made with mathematica 10tm discussions with marie calvet danilo galluzzo mario la rocca salvatore de lorenzo jessie mayor and ludovic margerin are gratefully acknowledged the authors are supported by medsuv european project and by spanish project ephestos cgl2011 29499 c02 01 and nowaves tec2015 68752 the tides eu travel cost action provided travel money to support cooperation between luca de siena and the other authors

joint hypocentral determination and the detection of low velocity anomalies an example from the phlegraean fields earthquakes abstract arrival time data from the phlegraean fields italy earthquake swarm recorded by the university of wisconsin array in 1983 to 1984 were reanalyzed using a joint hypocentral determination jhd technique the p and s wave station corrections computed as part of the jhd analysis show a circular pattern of central positive values surrounded by negative values whose magnitudes increase with distance from the center of the pattern this center roughly coincides with the point of the maximum uplift almost 2 m associated with the swarm corrections range from 0 85 to 0 10 sec for p wave arrivals and from 1 09 to 0 70 sec for s wave arrivals we interpret these patterns of corrections as caused by a localized low velocity anomaly in the epicentral area which agrees with the results of a previous 3 d velocity inversion of the same data set the relocated jhd epicenters show less scatter than the epicenters obtained in the velocity inversion and move more of the seismic activity to the vicinity of the only presently active fumarolic feature the capability of the jhd technique to detect low velocity anomalies and at the same time to give reliable locations particularly epicenters was verified using synthetic data generated for a 3 d velocity model roughly resembling the model obtained by velocity inversion

attenuation and scattering tomography of the deep plumbing system of mount st helens we present a combined 3 d p wave attenuation 2 d s coda attenuation and 3 d s coda scattering tomography model of fluid pathways feeding systems and sediments below mount st helens msh volcano between depths of 0 and 18 km high scattering and high attenuation shallow anomalies are indicative of magma and fluid rich zones within and below the volcanic edifice down to 6 km depth where a high scattering body outlines the top of deeper aseismic velocity anomalies both the volcanic edifice and these structures induce a combination of strong scattering and attenuation on any seismic wavefield particularly those recorded on the northern and eastern flanks of the volcanic cone north of the cone between depths of 0 and 10 km a low velocity high scattering and high attenuation north south trending trough is attributed to thick piles of tertiary marine sediments within the st helens seismic zone a laterally extended 3 d scattering contrast at depths of 10 to 14 km is related to the boundary between upper and lower crust and caused in our interpretation by the large scale interaction of the siletz terrane with the cascade arc crust this contrast presents a low scattering 4 6 km2 hole under the northeastern flank of the volcano we infer that this section represents the main path of magma ascent from depths greater than 6 km at msh with a small north east shift in the lower plumbing system of the volcano we conclude that combinations of different nonstandard tomographic methods leading toward full waveform tomography represent the future of seismic volcano imaging

aging of marine organic matter during cross shelf lateral transport in the benguela upwelling system revealed by compound specific radiocarbon dating organic matter accumulation and burial on the namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers much of the material deposited in depo centers on the slope ultimately derives from the shelf supply of organic matter from the shelf involves selective transport of organic matter we studied these selective transport processes by analyzing the radiocarbon content of co occurring sediment fractions here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity phytoplankton derived alkenones membrane lipids of pelagic crenarchaeota crenarchaeol and calcareous microfossils of planktic foraminifera in core top and near surface sediment samples the samples were collected on the namibian margin along a shelf slope transect 85 to 1040 m at 24 s and from the upper slope depo center at 25 5 s in core top sediments alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth crenarchaeol while younger than alkenones also increased in age with distance offshore it was concluded that the observed ages were a consequence of cross shelf transport and associated aging of organic matter radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied pre aged material present in a sample highlighting the importance of nepheloid transport for the sedimentation of organic matter over the namibian margin

constraining the applicability of organic paleotemperature proxies for the last 90 myrs abstract we evaluated changes in the distributions of long chain alkenones long chain diols and gdgts lipids commonly used for paleothermometry over the last 90 myrs for sediments deposited on the new jersey shelf the bass river site and assessed potential effects of different ancestral producers and diagenesis on their distributions and their impact on the associated temperature proxies as reported before the paleogene distributions of alkenones are generally similar to those in modern haptophytes but unusual alkenone distributions characterized by a dominant di unsaturated c40 alkenone are observed for late cretaceous sediments suggesting different ancestral source organisms for alkenones in this interval the isoprenoid gdgt distributions remained comparable to modern day distributions suggesting that tex86 can be applied up to ca 90 ma the miocene long chain diol distributions are similar to modern day distributions but the older sediments reveal unusual distributions dominated by the c28 1 12 and c26 1 13 diols suggesting different source organisms before 30 ma accordingly the ldi does not match other paleotemperature proxies suggesting its applicability might be compromised for sediments older than the miocene our results indicate that of the three proxies the tex86 seems to be the most applicable for deep time temperature reconstructions

spatial and temporal offsets between proxy records in a sediment drift chronologies for late quaternary marine sediment records are usually based on radiocarbon ages of planktonic foraminifera signals carried by other sedimentary components measured in parallel can provide complementary paleoclimate information a key premise is that microfossils and other indicators within a given sediment horizon are of equal age we show here that haptophyte derived alkenones isolated from bermuda rise drift sediments are up to 7000 years older than coexisting planktonic foraminifera this temporal offset which is apparently due to lateral transport of alkenones on fine grained particles from the nova scotian margin markedly influences molecular estimates of sea surface temperatures more broadly the observation raises questions about both the temporal and the geographic fidelity of paleoenvironmental records encoded by readily transported components of sediments

distributional variations in marine crenarchaeotal membrane lipids a new tool for reconstructing ancient sea water temperatures it has recently been shown that membrane lipids of marine crenarchaeota a ubiquitous and abundant component of plankton occur in relatively high concentrations in recent and ancient sediments in this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments we especially focussed on temperature as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature indeed a significant linear correlation r2 0 92 is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures this suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives in turn archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments

3d scattering image of the campi flegrei caldera southern italy new hints on the position of the old caldera rim abstract a scattering image of the campi flegrei caldera has been obtained using coda wave envelopes from local microearthquake data recorded at a portable 12 station digital network this was operated during the paroxysmic phase of the ground uplift bradyseism that occurred in the years 1983 1984 the nishigami technique has been used to obtain the 3d distribution of the strong scatterers in an earth volume with a horizontal extension of 20 km 20 km and a vertical thickness of 6 km this earth volume was segmented in blocks of 2 km 2 km 2 km for the outer section and in blocks of 1 km 1 km 1 km for the inner section the inversion was performed using a hybrid jackknife svd method that has allowed qualitative control of the stability and robustness of the solution the results show that the scatterers revealed by the coda envelopes which were band pass filtered at a center frequency of 18 hz match the inner border of the caldera rim which is well outlined on land by geological observations the scatterer position also delineates this border well beneath sea level these results are in close agreement with recently obtained seismic velocity tomography the scatterers imaged at the 6 and 12 hz band pass frequencies are located around the zone of maximum uplift beneath solfatara crater where most of the present residual volcanic activity is concentrated

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

diagenetic and sedimentological controls on the composition of organic matter preserved in california borderland basin sediments compound specific radiocarbon 14c contents stable carbon isotopes and abundances of phytoplankton and vascular plant derived lipid biomarkers alkenones and fatty acids were obtained from santa barbara basin and santa monica basin sediments along with radiocarbon contents of planktic foraminifera and total organic carbon we investigated core top and prebomb sediment intervals at sites from the flanks and depocenters of the basins deposited under contrasting bottom water oxygen concentrations bulk organic matter generally has the lowest radiocarbon levels of all sediment constituents measured whereas planktic foraminifera tend to be the most radiocarbon enriched alkenones are systematically depleted in radiocarbon with respect to foraminifera short chain c14 c 16 c 18 fatty acids decrease rapidly in absolute abundance and relative to longer chain c24 homologues from core top to prebomb samples the loss of short chain fatty acids with depth is associated with 13c depletion of short chain fatty acids indicating preferential preservation of terrestrially derived fatty acids short chain fatty acids tend to be more 14c enriched relative to alkenones in core top sediments whereas longerchain homologues are generally the most radiocarbon depleted of the lipids studied here less refractory compounds e g short chain fatty acids are thus enriched in radiocarbon with respect to more recalcitrant biomarkers alkenones long chain fatty acids the lower 14c content of more refractory compounds reflects a larger proportion of laterally supplied preaged material greater preservation of labile organic compounds observed at the depocenters than in flank sediments results in the presence of younger biomarkers underlining the important influence of selective degradation of labile compounds on their radiocarbon ages

appraisal of tex86 and tex86l thermometries in subpolar and polar regions tex86 tetraether index of tetraethers consisting of 86 carbon atoms is a sea surface temperature sst proxy based on the distribution of archaeal isoprenoid glycerol dialkyl glycerol tetraethers gdgts in this study we appraise the applicability of tex86 and view the mathml sourcetex86l in subpolar and polar regions using surface sediments we present tex86 and view the mathml sourcetex86l data from 160 surface sediment samples collected in the arctic the southern ocean and the north pacific most of the sst estimates derived from both tex86 and view the mathml sourcetex86l are anomalously high in the arctic especially in the vicinity of siberian river mouths and the sea ice margin plausibly due to additional archaeal contributions linked to terrigenous input we found unusual gdgt distributions at five sites in the north pacific high gdgt 0 crenarchaeol and gdgt 2 crenarchaeol ratios at these sites suggest a substantial contribution of methanogenic and or methanotrophic archaea to the sedimentary gdgt pool here apart from these anomalous findings tex86 and view the mathml sourcetex86l values in the surface sediments from the southern ocean and the north pacific do usually vary with overlaying ssts in these regions the sedimentary tex86 sst relationship is similar to the global calibration and the derived temperature estimates agree well with overlaying annual mean ssts at the sites however there is a systematic offset between the regional view the mathml sourcetex86l sst relationships and the global calibration at these sites temperature estimates based on the global view the mathml sourcetex86l calibration are closer to summer ssts than annual mean ssts this finding suggests that in these subpolar settings a regional view the mathml sourcetex86l calibration may be a more suitable equation for temperature reconstruction than the global calibration

multi scale reasonable attenuation tomography analysis murat an imaging algorithm designed for volcanic regions abstract the attenuation of body wave amplitudes with propagation distance can be used to provide detailed tomographic images of seismic interfaces fluid reservoirs and melt batches in the crust the high sensitivity of body wave energies to high scattering structures becomes an obstacle when we try to apply attenuation tomography to small scale volcanic media where we must take into account the complexities induced by strong heterogeneous scattering topography and uncertain source modeling in the recorded wave fields the murat code uses a source and site independent coda normalization method to obtain frequency dependent measurements of p to coda and s to coda energy ratios the code inverts these data for both the geometrical spreading factor and the spatially dependent quality factors q providing additional attenuation information in the regions where velocity tomography is available the high sensitivity of coda waves to highly heterogeneous structures highlights zones of anomalous scattering which may corrupt amplitude dependent attenuation measurements and where basal assumptions of linear optics may go unfulfilled a multi step tomographic inversion increases the stability of the results obtained in regions of high heterogeneity e g the volcanic edifice by the inclusion of data corresponding to either sources or stations located in regions of lower heterogeneity on the other hand a mere increase in the number of rays entirely contained in the heterogeneous structures affects both the stability and the effective resolution of the results we apply the code to two small waveform datasets recorded at an active mount st helens and at a quiescent mount vesuvius volcano the results show that the seismicity located inside or under the volcanic edifice produces an increase of the low frequency energy ratios with travel time in both areas in our interpretation the anomalous concentration of energy which affects any waveform recorded on the cone produced inside the volcanic edifice or in the feeding system of the volcano is due to seismic source or medium dependent resonance the results also provide spatial and frequency limits on the feasibility of attenuation tomography in these two regions with larger datasets

modelling of seismic energy transport at volcanoes with real topography and complex propagation medium abstract in stratovolcanoes multiple scattering of seismic waves is caused by a strongly heterogeneous propagation medium additionally these waves are scattered by the rough topography of the volcano we devised an algorithm to model seismic energy transport in volcanoes based on a monte carlo simulation of the equation of radiative transfer this algorithm takes into account both the real topography of volcanoes which is described by a digital elevation model and the complex subsurface structure of the volcanic edifice which is treated as a random medium theoretical energy densities of two different models were compared to observed energy densities derived from seismograms of shallow volcano tectonic earthquakes that occurred at merapi volcano indonesia a model consisting of a heterogeneous volcano shaped medium over a homogeneous half space was found to be suitable to explain the observed data for merapi volcano our modelling results in a mean free path of 250 m and a thickness of 1 7 km of the scattering volcanic edifice the systematic decrease of the coda energy with source distance of the observed data referred to as coda localization can be successfully explained by our model

a radiocarbon based assessment of the preservation characteristics of crenarchaeol and alkenones from continental margin sediments crenarchaeotal glycerol dibiphytanyl glycerol tetraether gdgt lipids and alkenones are two types of biomarkers derived from planktonic marine microorganisms which are used for reconstruction of sea surface temperature we determined the radiocarbon contents of the archaeal gdgt crenarchaeol and of alkenones isolated from continental margin sediments systematic differences were found between the two biomarkers with higher radiocarbon content in crenarchaeol than in the phytoplankton derived alkenones these differences can be explained by variable contributions of pre aged laterally advected material to the core sites crenarchaeol appears to be more efficiently degraded during transport in oxygen replete environments than alkenones whether this reflects the influence of chemical structure or mode of protection e g particle association is not known

millennial scale sea surface temperature changes in the eastern mediterranean nile river delta region over the last 27 000 years 1 in this study we utilize two organic geochemical proxies the u37k index and tex86 to examine past sea surface temperatures sst from a site located near the nile river delta in the eastern mediterranean em sea the u37k and tex86 records generally are in agreement and indicate sst ranges of 14 c 26 c and 14 c 28 c respectively during the last 27 cal ka during the holocene tex86 based sst estimates are usually higher than u37k based sst estimates which is likely due to seasonal differences between the timing of the haptophyte and crenarchaeota blooms in the em and is related to the onset of the modern flow regime of the nile river both records show that sst varied on centennial to millennial timescales in response to global climate events i e cooling during the last glacial maximum lgm heinrich event 1 h1 and the younger dryas yd and warming during the bolling allerod and in the early holocene during deposition of sapropel s1 the h1 cooling was particularly severe and is marked by a drop in sst of 4 5 c in comparison to pre h1 sst with temperatures 1 c cooler than during the lgm in contrast to high latitude and western mediterranean records which indicate both an abrupt onset and termination of the yd event the transition from the yd to the holocene was much more gradual in the em

effects of volcano topography on seismic broad band waveforms volcano seismology often deals with rather shallow seismic sources and seismic stations deployed in their near field the complex stratigraphy on volcanoes and near field source effects have a strong impact on the seismic wavefield complicating the interpretation techniques that are usually employed in earthquake seismology in addition as most volcanoes have a pronounced topography the interference of the seismic wavefield with the stress free surface results in severe waveform perturbations that affect seismic interpretation methods in this study we deal predominantly with the surface effects but take into account the impact of a typical volcano stratigraphy as well as near field source effects we derive a correction term for plane seismic waves and a plane free surface such that for smooth topographies the effect of the free surface can be totally removed seismo volcanic sources radiate energy in a broad frequency range with a correspondingly wide range of different fresnel zones a 2 d boundary element method is employed to study how the size of the fresnel zone is dependent on source depth dominant wavelength and topography in order to estimate the limits of the plane wave approximation this approximation remains valid if the dominant wavelength does not exceed twice the source depth further aspects of this study concern particle motion analysis to locate point sources and the influence of the stratigraphy on particle motions furthermore the deployment strategy of seismic instruments on volcanoes as well as the direct interpretation of the broad band waveforms in terms of pressure fluctuations in the volcanic plumbing system are discussed

selective aerobic and anaerobic degradation of lipids and palynomorphs in the eastern mediterranean since the onset of sapropel s1 deposition abstract selective degradation of organic matter in sediments is important for reconstructing past environments and understanding the carbon cycle here we report on compositional changes between and within lipid classes and kerogen types represented by palynomorph groups in relation to the organic matter flux to the sea floor and oxidation state of the sediments since the early holocene for central eastern mediterranean site abc26 this includes the initially oxic but nowadays anoxic presapropelic interval the still unoxidised lower part of the organic rich s1 sapropel its postdepositionally oxidised and nowadays organic poor upper part as well as the overlying postsapropelic sediments which have always been oxic a general 2 3 times increase in terrestrial and marine input during sapropel formation is estimated on the basis of the total organic carbon toc pollen spore dinoflagellate cyst n alkane n alkanol and n alkanoic acid concentration changes in the unoxidised part of the sapropel the long chain alkenones 1 15 diols and keto ols loliolides and sterols indicate that some plankton groups notably dinoflagellates may have increased much more apart from the terrestrial and surface water contributions to the sedimentary organic matter anomalous distributions and preservation of some c 23 c 27 alkanes alkanols and alkanoic acids have been observed which are interpreted as a contribution by organisms living in situ comparison of the unoxidised s1 sapropel with the overlying oxidised sapropel and the organic matter concentration profiles in the oxidised postsapropelic sediments demonstrates strong and highly selective aerobic degradation of lipids and palynomorphs there seems to be a fundamental difference in degradation kinetics between lipids and pollen which may be possibly related with the absence of sorptive preservation as a protective mechanism for palynomorph degradation the n alkanes impagidinium and nematosphaeropsis are clearly more resistant than toc the n alkanols and n carboxylic acids are about equally resistant whereas the pollen all other dinoflagellate cysts and other lipids appear to degrade considerably faster which questions the practice of normalising to toc without taking diagenesis into account selective degradation also modifies the relative distributions within lipid classes whereby the longer chain alkanes alcohols and fatty acids disappear faster than their shorter chain equivalents accordingly interpretation of lipid and palynomorph assemblages in terms of pre or syndepositional environmental change should be done carefully when proper knowledge of the postdepositional preservation history is absent two lipid based preservation proxies are tested the diol keto ol oxidation index based on the 1 15c 30 diol and keto ols doxi and the alcohol preservation index api whereby the former seems to be the most promising

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control

an evaluation of 14c age relationships between co occurring foraminifera alkenones and total organic carbon in continental margin sediments 1 radiocarbon age relationships between co occurring planktic foraminifera alkenones and total organic carbon in sediments from the continental margins of southern chile northwest africa and the south china sea were compared with published results from the namibian margin age relationships between the sediment components are site specific and relatively constant over time similar to the namibian slope where alkenones have been reported to be 1000 4500 years older than co occurring foraminifera alkenones were significantly similar to 1000 years older than co occurring foraminifera in the chilean margin sediments in contrast alkenones and foraminifera were of similar age within 2 sigma error or better in the nw african and south china sea sediments total organic matter and alkenone ages were similar off namibia age difference toc alkenones 200 700 years chile 100 450 years and nw africa 360 770 years suggesting minor contributions of preaged terrigenous material in the south china sea total organic carbon is significantly 2000 3000 years older owing to greater inputs of preaged terrigenous material age offsets between alkenones and planktic foraminifera are attributed to lateral advection of organic matter physical characteristics of the depositional setting such as seafloor morphology shelf width and sediment composition may control the age of co occurring sediment components in particular offsets between alkenones and foraminifera appear to be greatest in deposition centers in morphologic depressions aging of organic matter is promoted by transport age offsets are correlated with organic richness suggesting that formation of organic aggregates is a key process