simulating migrated and inverted seismic data by filtering a geologic model the simulation of migrated and inverted data is hampered by the high computational cost of generating 3d synthetic data followed by processes of migration and inversion for example simulating the migrated seismic signature of subtle stratigraphic traps demands the expensive exercise of 3d forward modeling followed by 3d migration of the synthetic seismograms this computational cost can be overcome using a strategy for simulating migrated and inverted data by filtering a geologic model with 3d spatial resolution and angle filters respectively a key property of the approach is this the geologic model that describes a target zone is decoupled from the macrovelocity model used to compute the filters the process enables a target orientedapproach by which a geologically detailed earth model describing a reservoir is adjusted without having to recalculate the filters because a spatial resolution filter combines the results of the modeling and migration operators the simulated images can be compared directly to a real migration image we decompose the spatial resolution filter into two parts and show that applying one of those parts produces output directly comparable to 1d inverted real data two dimensional synthetic examples that include seismic uncertainties demonstrate the usefulness of the approach results from a real data example show that horizontal smearing which is not simulated by the 1d convolution model result is essential to understand the seismic expression of the deformation related to sulfate dissolution and karst collapse

shallow virtual source redatuming by multi dimensional deconvolution recently new on shore acquisition designs have been presented with multicomponent sensors deployed in the shallow sub surface 20 m 60 m virtual source redatuming has been proposed for these data to compensate for surface statics and to enhance survey repeatability in this paper we investigate the feasibility of replacing the correlation based formalism that undergirds virtual source redatuming with multi dimensional deconvolution offering various advantages such as the elimination of free surface multiples and the potential to improve virtual source repeatability to allow for data driven calibration of the sensors and to improve robustness in cases with poor sensor spacing in the shallow sub surface resulting in a relatively high wavenumber content we propose a new workflow for this configuration we assume a dense source sampling and target signals that arrive at near vertical propagation angles first the data are preconditioned by applying synthetic aperture source filters in the common receiver domain virtual source redatuming is carried out for the multi component recordings individually followed by an intermediate deconvolution step after this specific pre processing we show that the downgoing and upgoing constituents of the wavefields can be separated without knowledge of the medium parameters the source wavelet or sensor characteristics as a final step free surface multiples can be eliminated by multi dimensional deconvolution of the upgoing fields with the downgoing fields

point spread functions for interferometric imaging interferometric redatuming is a data driven method to transform seismic responses with sources at one level and receivers at a deeper level into virtual reflection data with both sources and receivers at the deeper level although this method has traditionally been applied by cross correlation accurate redatuming through a heterogeneous overburden requires solving a multidimensional deconvolution problem input data can be obtained either by direct observation for instance in a horizontal borehole by modelling or by a novel iterative scheme that is currently being developed the output of interferometric redatuming can be used for imaging below the redatuming level resulting in a so called interferometric image internal multiples from above the redatuming level are eliminated during this process in the past we introduced point spread functions for interferometric redatuming by cross correlation these point spread functions quantify distortions in the redatumed data caused by internal multiple reflections in the overburden in this paper we define point spread functions for interferometric imaging to quantify these distortions in the image domain these point spread functions are similar to conventional resolution functions for seismic migration but they contain additional information on the internal multiples in the overburden and they are partly data driven we show how these point spread functions can be visualized to diagnose image defocusing and artefacts finally we illustrate how point spread functions can also be defined for interferometric imaging with passive noise sources in the subsurface or with simultaneous source acquisition at the surface

dating the cooloola coastal dunes of south eastern queensland australia abstract the cooloola sand dunes are part of a series of aeolian parabolic dunes that stretch along the east coast of australia they form a chronosequence showing increasing weathering soil formation and water erosion across six geomorphically recognized soil landscapes these landscapes were recognized from air photographs and further refined on the basis of some 150 auger holes across the dunes data about the structure and floristics of the vegetation were collected at the same time there is a significant body of literature about the cooloola dunes but there are two areas that have not been satisfactorily considered first the previous dating which gave inconsistent results has been superseded by single grain osl dates and second cooloola has not been considered in a regional context here we report the results of single grain optically stimulated luminescence osl analyses for 31 samples for 21 sites across the geomorphic landscapes the sites were selected near the apex of each dune as this represents the last depositional date and the least disturbed by sand movement we recognized 10 units across the dunes on the basis of the dates available the dune ages ranged from recent to 725 ka the largest dunes at some 320 m high were dated at around 140 ka and these dunes carry the maximum vegetation biomass of this dunefield beyond this vegetation maximum the dunes had lost their parabolic shape due to prolonged weathering and erosion and the vegetation is greatly reduced in height and biomass the depth to the soil b horizon gradually deepens with age to form giant podzols in the older dunes the depth to the b horizon was remarkably consistent within the geomorphic landscapes across the length and breadth of the dunes these studies place the cooloola dunes in a unique position as the chronosequence is intact the possible processes that lead to the formation of the dunes and the regional implications are discussed secondly it shows the buildup and decline of the dune ecosystems and acts as a model for all ecosystems forest succession models which place less emphasis on soil development miss this important process

seismic interferometry application to improve seismic reflection signals affected by ice plate flexural noise seismic interferometry based on cross correlation of traces recorded at different positions makes it possible to recover new green s functions and to obtain signals as if sources were placed at the receiver positions this case history describes results obtained using sea bottom hydrophone signals recorded in shallow water below the ice plate in an alaska seismic survey the aim was to simulate new shots at the sea bottom receiver positions and to redatum the surface generated seismic signals below the ice layer the application was performed and the method investigated to attenuate the strong noise due to dispersive wave modes mainly flexural waves which propagate in the ice layer

seismic modelling for reservoir studies a comparison between convolutional and full waveform methods for a deep water turbidite sandstone reservoir abstract two seismic modelling approaches that is two dimensional pre stack elastic finite difference and one dimensional convolution methods are compared in a modelling exercise over the fluid flow simulation model of a producing deep water turbidite sandstone reservoir in the west of shetland basin if the appropriate parameterization for one dimensional convolution is used the differences in three dimensional and four dimensional seismic responses from the two methods are negligible the key parameters to ensure an accurate seismic response are a representative wavelet the distribution of common depth points and their associated angles of incidence conventional seismic images generated by the one dimensional convolutional model suffer from lack of continuity because it only accounts for vertical resolution after application of a lateral resolution function the convolutional and finite difference seismic images are very similar although transmission effects internal multiples and p to s conversions are not included in our convolutional modelling the subtle differences between images from the two methods indicates that such effects are of secondary nature in our study a quantitative comparison of the normalized root mean square amplitude attributes and waveform kinematics indicates that the finite difference approach does not offer any tangible benefit in our target oriented seismic modelling case study and the potential errors from one dimensional convolution modelling are comparatively much smaller than the production induced time lapse changes

palaeolithic landscapes of europe and environs 150 000 25 000 years ago an overview abstract when considering the evolution and migrations of neandertalers and early modem human beings the harsh conditions of the last glacial maximum are often implicitly or explicitly assumed as their environmental background this perception is false the conditions of the high glacial apply to a small fraction of late pleistocene time here we review the palaeoenvironmental history of europe from 150 000 to 25 000 years ago with the aid of data from long cores of ice and marine and continental sediments the results are displayed in four sketch maps that illustrate the landscapes of an interglacial glacial cycle the maps connected by palaeoenvironmental histories show that especially between 60 000 and 25 000 years ago a critical part of the palaeolithic the glacial landscapes were for much of the time less barren than is generally assumed but numerous climate changes on a scale of several millennia are evident placing a premium on accurate dating of the co evolution of humans and landscape moreover during the glacial interval abrupt climatic changes lasting from a century to a few millennia were common their importance for landscape changes and their impact on human activity remain to be ascertained

age estimates for the late quaternary high sea stands abstract a database of more than 300 published alpha counted uranium series ages has been compiled for coral reef terraces formed by late pleistocene high sea stands the database was screened to eliminate unreliable age estimates 230 th 232 th 5 and those without quoted without quoted errors and a distributed error frequency curve was produced this curve can be considered as a finite mixture model comprising k component normal distributions each with a weighting by using an expectation maximising algorithm the mean and standard deviation of the component distributions each corresponding to a high sea level event were estimated eight high sea stands with mean and standard deviations of 129 0 33 0 123 0 13 0 102 5 2 0 81 5 5 0 61 5 6 0 50 0 1 0 40 5 5 0 and 33 0 2 5 ka were resolved the standard deviations are generally larger than the values quoted for individual age estimates whilst this may be due to diagenetic effects especially for the older corals it is argued that in many cases geological evidence clearly indicates that the high stands are multiple events often not resolvable at sites with low rates of uplift the uranium series dated coral reef terrace chronology shows good agreement with independent chronologies derived for antarctic ice cores although the resolution for the latter is better agreement with orbitally tuned deep sea core records is also good but it is argued that isotope stage 5e is not a single event as recorded in the cores but a multiple event spanning some 12 ka the much earlier age for isotope stage 5e given by winograd et al 1988 is not supported by the coral reef data but further mass spectrometric uranium series dating is needed to permit better chronological resolution

eustatic and tectonic controls upon quaternary coastal sedimentation in the corinth basin greece the late quaternary sedimentology and palaeogeography of the corinth isthmus in central greece is re interpreted a series of beach to shoreface sub sequences are seen each characteristically having an overall fining up character these occur within a coastal facies belt which has prograded to the west computer modelling illustrates the interaction of tectonic displacements and eustatic sea level variation as controls of facies patterns late pleistocene holocene facies geometries are predicted on the basis of published sea level data over that time interval on coastlines undergoing tectonic uplift such as the isthmus of corinth depositional patterns may be characterized by transgressive wedges these sub sequences merge basinwards below sea level minima each transgression relates to a major eustatic sea level peak such first order models are modified by variations in the rate of tectonic deformation the second control on relative sea level position modelled facies patterns are tested on the basis of new 230 th 234 u dates obtained from sclerac tinian corals of the corinth canal area dated sub sequence sediments correspond in age to late pleistocene eustatic highs and observed facies patterns correlate with the major late pleistocene holocene eustatic transgressions of c 100 ka periodicity episodes of intrabasinal normal faulting are isolated from a structural history otherwise dominated by uplift across the isthmus quantification of post depositional vertical tectonic displacements is achieved constraining the eustatic base level at the time of deposition of a dated horizon by reference to the global late quaternary sea level curve the original depositional level is then subtracted from the present outcrop level using available 230 th 234 u dates to establish syn depositional base levels minimum uplift rates of the order of 0 3 m ka 1 are calculated across the area averaged through the late pleistocene and holocene

virtual source method applied to crosswell and horizontal well geometries the virtual source method is a useful tool for redatuming a seismic survey below complicated overburden by creating virtual sources at downhole receiver locations hence generating data independent of the overburden and the time lapse changes therein in this article we first apply this technique to crosswell geometries whereby a virtual crosswell survey is simulated by shooting a line of surface shots passing through two boreholes instrumented with downhole sensors using this acquisition geometry receivers in one of the two wells are turned into virtual sources by correlating the wavefield recorded by those receivers with the recording at receivers in the other well and summing the correlated data over the surface shots

interferometric imaging of the underside of a subducting crust summary seismic interferometry provides tools for redatuming physical data to a new source location turning a source located close to a structure of interest into a virtual receiver has the potential benefit of improving the quality of imaging by increasing the effective aperture and mitigatingtheeffectofvelocityuncertaintyintheoverburden here weconsidertheproblemof estimatingthegreen sfunctionbetweentwoearthquakeslocatedinsideasubductingslabusing earthquake data recorded at the surface our primary focus is to obtain an accurate time image of the subducting interface we propose a novel two step kinematically correct redatuming procedure that first redatums the data from earthquakes below the subducting interface to the surface via classical interferometry and then utilizes source receiver wavefield interferometry to redatum virtual surface seismic data to the location of a particular earthquake event

source receiver interferometric redatuming using sparse buried receivers to address complex near surface environments a case study of seismic imaging quality and time lapse repeatability

the last interglacial shoreline in australia a review abstract marginal marine strata of last interglacial age occur in a range of morphostratigraphic settings around the australian coastline the lithofacies are similar to their holocene equivalents but are partly lithified elevated and laterally displaced inland uranium series ages for corals and molluscs from widely separated localities around the australian coastline are generally in accord with the accepted age for oxygen isotope substage 5e 125 000 10 000 bp the value generally accepted for the last interglacial maximum amino acid racemisation has principally been applied to correlation of sequences with benchmark sites dated by the uranium series method elevations of preserved last interglacial shorelines do not support the notion that australia is a stable continent significant neotectonic anomalies include cape cuvier 10 5 m fleurieu peninsula 6 m the coorong coastal plain 10 m and tasmania 32 m each indicating contrasting degrees of local uplift the tasmanian sequences are the highest occurrence on the australian continent and have been attributed to uplift as a result of mantle hotspot processes with the exception of these tectonically uplifted sites the height of the last interglacial sea surface around the australian coastline is consistently below the 6 m level globally attributed to this high sea level stand in australia the most consistent datum is from western eyre peninsula where a level 2 m above present mean sea level is ubiquitous the more southerly limit of coral growth and wider distribution of subtropical molluscan fauna are in accordance with warmer ocean waters during substage 5e approximately 2 c the extent of racemisation in molluscan fossils from southern australia also excludes the possibility of a more equable latitudinal distribution of mat during substage 5e

local vertical seismic profiling vsp elastic reverse time migration and migration resolution salt flank imaging with transmitted p to s waves to avoid the defocusing effects of propagating waves through salt and overburden with an inaccurate overburden velocity model we introduce a vertical seismic profiling vsp local elastic reverse time migration rtm method for salt flank imaging by transmitted p to s waves this method back projects the transmitted ps waves using a local velocity model around the well until they are in phase with the back projected pp waves at the salt boundaries the merits of this method are that it does not require the complex overburden and salt body velocities and it automatically accounts for source side statics in addition the method accounts for kinematic and dynamic effects including anisotropy absorption and all other unknown rock effects outside of this lo cal subsalt velocity model numerical tests on an elastic salt model and offset 2d vsp data in the gulf of mexico using a finite difference time domain staggered grid rtm scheme partly demonstrate the effectiveness of this method over interferometry

metal sources for the polymetallic ni mo pge mineralization in the black shales of the lower cambrian niutitang formation south china abstract total organic carbon content toc trace element and platinum group element pge concentrations were determined in the black shales of the lower cambrian niutitang formation in the nayong area guizhou province south china in order to study the polymetallic ni mo pge mineralization the results demonstrate that numerous elements are enriched in the polymetallic ores compared to those of the nearby black shale particularly ni mo zn toc and total pge which can reach up to 7 03 wt 8 49 wt 11 7 wt 11 5 wt and 943 ppb respectively the elemental enrichment distribution patterns are similar to those in the zunyi and zhangjiajie areas except that the nayong location is exceptionally enriched in zn whereas positive correlations are observed between the ore elements of the polymetallic ores no such correlations are observed in the black shale these positively correlated metallic elements are classified into three groups co ni cu pge zn cd pb and mo tl toc the geological and geochemical features of these elements suggest that proterozoic and early palaeozoic mafic and ultramafic rocks dolomites and or pb zn deposits of the neoproterozoic dengying formation and seawater could be the principal sources for co ni cu pge zn cd pb and mo tl toc respectively furthermore the chondrite normalized patterns of pges with pd pt pd ir and pt ir indicate that pge enrichment of the polymetallic ores is most likely related to hydrothermal processes associated with the mafic rocks in contrast pge enrichment in the black shale resembles that of the marine oil shale with terrigenous and seawater contributions our investigations of toc trace elements and pge geochemistry suggest that multiple sources along with submarine hydrothermal and biological contributions might be responsible for the formation of the polymetallic ni mo pge mineralization in the black shales of the lower cambrian niutitang formation across southern china

extreme enrichment of polymetallic ni mo pge au in lower cambrian black shales of south china an os isotope and pge geochemical investigation extreme metal enrichments occur in the lower cambrian niutitang formation a thick black shale sequence deposited on the yangtze platform of south china and form a regionally distributed conformable polymetallic ni mo pge au sulfide horizon the origin for the extreme enrichment of metals in these black shales is discussed based on a comprehensive geochemical investigation of re os isotopes and platinum group elements the black shales of the lower cambrian niutitang formation in guizhou province yielded an re os isochron age of 535 11 ma with an initial 187 os 188 os ratio of 0 80 0 04 which is similar to the initial 187 os 188 os ratio 0 78 0 19 of the ni mo sulfide ores but slightly lower than the initial 187 os 188 os ratio 1 18 0 02 of lower cambrian black shales from the lesser himalaya india a comparison of os isotope data among the chinese ni mo sulfide ores the seafloor massive sulfide deposits and contemporaneous seawater suggests a possible similar hydrothermal forming mechanism for these deposits the pge concentrations pt anomaly pt pt pt pd ir pd au pd ratios of the chinese ni mo sulfide ores are similar to those metal rich black shales of submarine volcanogenic hydrothermal origin from czech republic namibia and canada but are different from those data of the ocean floor fe mn crusts that have scavenged their pge and other metals directly from seawater it is therefore suggested that the ni mo sulfide ores from the niutitang black shale sequence in south china had a submarine hydrothermal origin the anoxic environments and abundant organic matter in the ocean basin also played a key role for the extreme metal enrichments the discharge of hydrothermal fluids into the cambrian ocean may have had a great effect on life during the cambrian explosion 2007 elsevier b v all rights reserved

seismic interferometry using multidimensional deconvolution and crosscorrelation for crosswell seismic reflection data without borehole sources crosswell reflection method is a high resolution seismic imaging method that uses recordings between boreholes the need for downhole sources is a restrictive factor in its application for example to time lapse surveys an alternative is to use surface sources in combination with seismic interferometry seismic interferometry si could retrieve the reflection response at one of the boreholes as if from a source inside the other borehole we investigate the applicability of si for the retrieval of the reflection response between two boreholes using numerically modeled field data we compare two si approaches crosscorrelation cc and multidimensional deconvolution mdd si by mdd is less sensitive to underillumination from the source distribution but requires inversion of the recordings at one of the receiver arrays from all the available sources we find that the inversion problem is ill posed and propose to stabilize it using singular value decomposition the results show that the reflections from deep boundaries are retrieved very well using both the cc and mdd methods furthermore the mdd results exhibit more realistic amplitudes than those from the cc method for downgoing reflections from shallow boundaries we find that the results retrieved from the application of both methods to field data agree well with crosswell seismic reflection data using borehole sources and with the logged p wave velocity

podzol chronosequences on coastal dunes of eastern australia chronosequences of freely drained podzols formed in extensive dune systems of quartz sands along the east coast of australia offer unique opportunities for comparing temporal changes in different climatic zones during the late quarternary the largest areas and greatest number of dune systems occur along the subtropical coast near brisbane here parts of six dune systems have not been covered by younger deposits and have been exposed to weathering since deposition these areas constitute a relative age sequence on which podzols have formed with solum depths varying with age from 20 m absolute ages for each system have not been determined but differences in erosion and weathering depths and comparisons with dated dunes elsewhere along the coast indicate an age sequence extending back at least to the last interglacial similarities in geomorphology and soils enable correlation with dune systems in other areas to the north and south and so provide a greater potential for examining temporal changes in soils and biological systems than that of previous soil chronosequences1 5

selenium speciation in lower cambrian se enriched strata in south china and its geological implications abstract to understand the impact of selenium se into the biogeochemical cycle and implications for palaeo redox environment a sequential extraction method was utilized for samples including black shales cherts a ni mo se sulfide layer k bentonite and phosphorite from lower cambrian se enriched strata in southern china seven species water soluble phosphate exchangeable base soluble acetic acid soluble sulfide selenide associated residual se and different oxidation states selenate se vi selenite se iv organic se se 0 and mineral se ii were determinated in this study we found that the ni mo se sulfide layer contained a significantly greater amount of se ii associated with sulfides selenides than those in host black shales and cherts furthermore a positive correlation between the degree of sulfidation of iron dos and the percentage of the sulfide selenide associated se ii was observed for samples which suggests the proportion of sulfide selenide associated se ii could serve as a proxy for palaeo redox conditions in addition the higher percentage of se iv in k bentonite and phosphorite was found and possibly attributed to the adsorption of se by clay minerals iron hydroxide surfaces and organic particles based on the negative correlations between the percentage of se iv and that of se ii in samples we propose that the k bentonite has been altered under the acid oxic conditions and the most of black shale and cherts and the ni mo se sulfide layer formed under the anoxic and euxinic environments respectively concerning se accumulation in the ni mo se sulfide layer the major mechanism can be described by 1 biotic and abiotic adsorption and further dissimilatory reduction from oxidized se vi and se iv to se ii through elemental se 2 contribution of hydrothermal fluid with mineral se ii

re os dating of polymetallic ni mo pge au mineralization in lower cambrian black shales of south china and its geological significance a discussion sir thirty years ago fan et al 1973 reported an entirely new type of ore from cambrian black shales of south china containing percent values for ni mo as and in some cases zn together with substantial amounts of pt pd and au 100 1 000 ppb subsequently chen et al 1982 and fan 1983 described additional ni mo ore bed occurrences in a 1 600 km belt between kunming and hangzhou mao et al 2002 p 1057 describe the deposits as a thin layer having a wide lateral extent over hundreds of kilometers in southern china that contrasts with the lenticular shape of exhalative deposits which are usually located near hydrothermal vents and are continuous over only a few kilometers at most actually the known shale hosted ni mo deposits of china do consist of restricted lenticular occurrences that are clustered in eight relatively small areas lott et al 1999 near zunyi the principal but now exhausted deposit on tianeshan measures approximately 150 by 1 000 m in plan view and gaps occur between it and outliers at tuanshanbao and xintugou lott et al 1999 these deposits in turn are separated by 5 to 7 km from the newly described mineralized zone at huangjiawan mine mao et al 2002 the thicknesses of ni mo ore beds or lenses are extremely variable typically ranging from 1

gypsum in modern kamchatka volcanic hot springs and the lower cambrian black shale applied to the microbial mediated precipitation of sulfates on mars gypsum is a mineral that commonly precipitates in hydrothermal environments this study reports the electron microscopic analyses of gypsum morphologies and crystal sizes found in hot springs on the kamchatka peninsula russia and compares these analyses with gypsum morphologies of hydrothermal genesis found in lower cambrian black shale in sediments of the kamchatka hot springs we observed prismatic prismatic pseudo hexagonal fibrous tubular lenticular and twinned gypsum crystals with crystal sizes ranging from 200 m the coexistence of diverse crystal habits of gypsum implies a constant interaction between hot spring geochemistry and the metabolisms of the microbial community the crystallization of ca and ba sulfates in the black shale of the lower cambrian which shows similar but less varied morphology was influenced by post depositional hydrothermal fluids the partial replacement of pyrite by sulfates in a situation coexisting with rich biomass deposits and animal fossils indicates limited modification of the sedimentary records by biological materials if the gypsum precipitated on mars underwent similar interactions between microbial communities and their geochemical environments the resulting crystal habits could be preserved even better than those on earth due to the weak geodynamics prevailing on mars throughout its evolutionary history

time lapse monitoring of internal erosion in earthen dams and levees using ambient seismic noise earthen dams and levees are prone to progressive failure through internal erosion of their structure internal erosion is often invisible to current methods of inspection until it manifests itself

hydrogen sulphide release to surface waters at the precambrian cambrian boundary changes in environmental conditions at the precambrian cambrian transition around 542 million years ago have been suggested as a possible explanation for the apparent rapid increase in abundance of multicellular organisms known as the cambrian explosion the nature of the environmental changes is still a matter of debate however wille et al now report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of about 542 million years with the help of a box model of the oceanic molybdenum cycle they find that intense upwelling of hydrogen sulphide rich deep ocean water best explains the observed early cambrian molybdenum isotope signal this suggests that the early cambrian animal radiation may have been triggered by a major change in ocean circulation following a long period during which the ocean was stratified with sulphidic deep water this paper reports molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 million years the findings suggest that the early cambrian animal radiation may have been triggered by a major change in ocean circulation terminating a long period during which the proterozoic ocean was stratified with sulphidic deep water animal like multicellular fossils appeared towards the end of the precambrian followed by a rapid increase in the abundance and diversity of fossils during the early cambrian period an event also known as the cambrian explosion 1 2 3 changes in the environmental conditions at the precambrian cambrian transition about 542 myr ago have been suggested as a possible explanation for this event but are still a matter of debate1 2 3 here we report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 myr we find a transient molybdenum isotope signal immediately after the precambrian cambrian transition using a box model of the oceanic molybdenum cycle we find that intense upwelling of hydrogen sulphide rich deep ocean water best explains the observed early cambrian molybdenum isotope signal our findings suggest that the early cambrian animal radiation may have been triggered by a major change in ocean circulation terminating a long period during which the proterozoic ocean was stratified with sulphidic deep water

a new approach to separate seismic time lapse time shifts in the reservoir and overburden abstractfor a robust way of estimating time shifts near horizontal boreholes we have developed a method for separating the reflection responses above and below a horizontal borehole together with the surface reflection data the method uses the direct arrivals from borehole data in the marchenko method the first step is to retrieve the focusing functions and the up down wavefields at the borehole level using an iterative marchenko scheme the second step is to solve two linear equations using a least squares minimizing method for the two desired reflection responses then the time shifts that are directly linked to the changes on either side of the borehole are calculated using a standard crosscorrelation technique the method is applied with good results to synthetic 2d pressure data from the north sea one example uses purely artificial velocity changes negative above the borehole and positive below and the other example uses more realistic changes based on well logs in the 2d case with an adequ

metal source and fluid rock interaction in the archean bif hosted lamego gold mineralization microthermometric and la icp ms analyses of fluid inclusions in quartz veins rio das velhas greenstone belt brazil the lamego orogenic gold deposit 440 742 oz gold measured reserves and 2 4 million t measured resources with an average grade of 5 71 g t au and a cut off grade of 2 15 g t au anglogold ashanti corrego do sitio mineracao s a aga personal communication 2014 is located in the 5 km long trend that includes the world class cuiaba deposit it is hosted in the neoarchean metavolcano sedimentary rocks of the rio das velhas greenstone belt quadrilatero ferrifero brazil mineralization is associated mainly with metachert banded iron formation bif and carbonaceous phyllites in the reclined lamego fold in which the cabeca de pedra orebody represents the hinge zone mineralization is concentrated in silicification zones and their quartz veins as well as in sulfide minerals product of bif sulfidation hydrothermal alteration varies according to host rock with abundant sulfide carbonate in bif and sericite chlorite in carbonaceous phyllite quartz vein classification according to structural relationships and host rocks identified three vein systems the v1 system mainly composed of smoky quartz qtz i and pyrite is extensional crosscuts the bedding plane s0 of bif and is parallel to the fold axis the v2 system of the same composition is represented by veins that are parallel to the s1 2 foliation and s0 this system is also characterized by silicification zones in the bif carbonaceous phyllite contact that has its maximum expression in the hinge zone of folds the v3 system has milky quartz qtz ii veins which result from the recrystallization of smoky quartz located mainly in shear zones and faults these veins form structures en echelon and vein arrays the most common ore minerals are pyrite as pyrite and arsenopyrite fluid inclusion fi trapped in all quartz veins present composition in the h2o co2 ch4 nacl system fluid evolution can be interpreted in two stages i aqueous carbonic fluid trapped in qtz i of low salinity 2 equiv wt nacl and ii carbonic aqueous fluid of moderate salinity average 9 eq wt nacl hosted in qtz ii both stages are characterized by decrepitation temperatures in the range of 200 to 300 c and suggest a fluid of metamorphic origin applying an arsenopyrite geothermometer the calculated formation temperature for the cabeca de pedra orebody is 300 to 375 c the vertical intersection of the isochors allows a minimum pressure calculation of 2 6 kbar the composition of individual fis of this orebody obtained by la icp ms analyses compared with results of fis for the carvoaria velha deposit corrego do sitio lineament highlights a standard composition typical of metamorphic fluids with na k ca mg which increase or decrease in concentration as a function of salinity in both deposits trace elements vary according to fluid rock reactions and are directly related to the host rock composition the comparison of data sets of the two deposits shows that the cabeca de pedra fis have a higher enrichment in zn while cu as and sb are richer in carvoaria velha suggesting influence of the host rock geochemistry the suggested mechanisms for gold precipitation at the cabeca de pedra orebody lamego gold deposit are i hydrolysis of the carbonaceous matter of phyllite and bif affecting fo2 destabilizing sulfur complexes and enhancing gold precipitation ii replacement of bif iron carbonates by sulfides and iii continuous pressure changes that lead to silica precipitation and free gold other than playing the long recognized role of the carbonaceous phyllites as a fluid barrier the data highlight their importance as a source of metals

theory of supervirtual refraction interferometry summary inverting for the subsurface velocity distribution by refraction traveltime tomography is a well accepted imaging method by both the exploration and earthquake seismology communities a significant drawback however is that the recorded traces become noisier with increasing offset from the source position and so accurate picking of traveltimes in far offset traces is often prevented to enhance the signal to noise ratio snr of the far offset traces we present the theory of supervirtual refraction interferometry where the snr of far offset head wave arrivals can be theoretically increased by a factor proportional to here n is the number of receiver or source positions associated with the recording and generation of the head wave arrival there are two steps to this methodology correlation and summation of the data to generate traces with virtual head wave arrivals followed by the convolution of the data with the virtual traces to create traces with supervirtual head wave arrivals this method is valid for any medium that generates head wave arrivals recorded by the geophones results with both synthetic traces and field data demonstrate the feasibility of this method there are at least four significant benefits of supervirtual interferometry 1 an enhanced snr of far offset traces so the first arrival traveltimes of the noisy far offset traces can be more reliably picked to extend the useful aperture of the data 2 the snr of head waves in a trace that arrive later than the first arrival can be enhanced for accurate traveltime picking and subsequent inversion by later arrival traveltime tomography 3 common receiver pair gathers can be analysed to detect the presence of diving waves in the first arrivals which can be used to assess the nature of the refracting boundary and 4 the source statics term is eliminated in the correlation operations so that the timing of the virtual traces is independent of the source excitation time this suggests the possibility of applying this method to earthquake data recorded by receivers that are inline with the refraction paths and source locations

the use of vsp techniques for fault zone characterization an example from the san andreas fault vertical seismic profiling vsp technology is increasingly being used in the fields of earthquake seismology and tectonics this is motivated in part by the growing number of oil field microseismic monitoring surveys but more so by projects that involve drilling deep wells for monitoring crustal activity at depth examples of these projects are the san andreas fault observatory at depth safod the nankai trough seismogenic zone experiment the gulf of corinth rift laboratory and the taiwan chelungpu fault drilling project and other projects by the international continental and ocean drilling programs icdp and iodp these projects require instrumentation and surveying in deep and possibly hot borehole environments with higher resolution than surface seismic data images from 2d and 3d vsp data contribute to better characterization and interpretation of complex reservoirs at smaller scales the location of receivers in the low noise borehole environment yields higher signal to noise ratios higher

evidence of high sea level during isotope stage 5c in queensland australia abstract thirty nine species of scleractinian corals have been recovered from under a high dune on the western mainland side of north stradbroke island eastern australia the corals are associated with thin intertidal sediments and their good condition implies burial in situ and preservation in a saturated zone most likely this occurred as the coast prograded and a large dune advanced into the littoral zone burying intertidal sediments and coral the species assemblage indicates a sheltered environment but one open to the ocean without wide fluctuations in salinity three species yielded a mean 230 th 234 u age of 105 000 yr b p which is significantly younger than the nearest pleistocene corals at evans head new south wales the corals provide evidence of a sea stand near present sea level during isotope stage 5c which is considerably higher than previously suggested for this period their good condition implies that the overlying parabolic dune is of comparable age and formed during that high stand of sea level also the isotope age provides a maximum period for the development of giant podzols in the podzol chronosequences on coastal dunes in southern queensland

interferometric interpolation of sparse marine data we present the theory and numerical results for interferometrically interpolating 2d and 3d marine surface seismic profiles data for the interpolation of seismic data we use the combination of a recorded green s function and a model based green s function for a water layer model synthetic 2d and 3d and field 2d results show that the seismic data with sparse receiver intervals can be accurately interpolated to smaller intervals using multiples in the data an up and downgoing separation of both recorded and model based green s functions can help in minimizing artefacts in a virtual shot gather if the up and downgoing separation is not possible noticeable artefacts will be generated in the virtual shot gather as a partial remedy we iteratively use a non stationary 1d multi channel matching filter with the interpolated data results suggest that a sparse marine seismic survey can yield more information about reflectors if traces are interpolated by interferometry comparing our results to those of f k interpolation shows that the synthetic example gives comparable results while the field example shows better interpolation quality for the interferometric method

a review of age determinations on pleistocene corals in eastern australia abstract samples of corals from all three previously reported pleistocene localities in eastern australia have been dated anew using the 230 th 234 u technique results for two sites are confirmed but the new results for the third site are older than previously reported and do not support a high sea level for isotope substage 5c all sites are now referred to substage 5e

sea level history 45 000 to 30 000 yr b p inferred from benthic foraminifera gulf st vincent south australia surficial sediments of gulf st vincent south australia are predominantly bioclastic cool temperate carbonates benthic foraminifera are abundant and distribution of species is closely related to water depth for example massilina milletti is most common at depths ca 40 m while discorbis dimidiatus is characteristics of shallow subtidal environments elphidium crispum a shallow water species and e macelliforme favoring deeper water provide a useful numerical ratio their logarithmic relative abundance in the sediment size fraction 0 50 0 25 mm correlates strongly with water depth vibrocores sv 4 and sv 5 recovered undisturbed sections of quaternary strata from the deepest part ca 40 m of gulf st vincent amino acid racemization and radiocarbon age determinations show that late pleistocene sections of the cores were deposited over the time ca 45 000 to 30 000 yr b p species of fossil foraminifera recovered from these sections are mostly extant in modern gulf st vincent thus allowing paleoecological inferences of late pleistocene sea levels these inferred sea level maxima can be correlated with those determined from study of huon peninsula coral reef terraces initial estimates of tectonically corrected sea levels for transgressions in gulf st vincent at 40 000 and 31 000 yr b p are 22 5 m and 22 m respectively the intervening regression lowered sea level to 28 m

distributed acoustic sensing for reservoir monitoring with vertical seismic profiling distributed acoustic sensing is a novel technology for seismic data acquisition particularly suitable for vertical seismic profiling it is a break through for low cost on demand seismic monitoring of reservoirs both onshore and offshore in this article we explain how distributed acoustic sensing works and demonstrate its usability for typical vertical seismic profiling applications such as checkshots imaging and time lapse monitoring we show numerous data examples and discuss distributed acoustic sensing as an enabler of seismic monitoring with 3d vertical seismic profiling key words borehole geophysics acquisition seismics time lapse monitoring

application of seismic interferometry to extract p and s wave propagation and observation of shear wave splitting from noise data at cold lake alberta canada we extract downward propagating p and s waves from industrial noise generated by human and or machine activity at the surface propagating down a borehole at cold lake alberta canada and measure shear wave splitting from these data the continuous seismic data are recorded at eight sensors along a downhole well during steam injection into a 420 470 m deep oil reservoir we crosscorrelate the waveforms observed at the top sensor and other sensors to extract estimates of the direct p and s wave components of the green s function that account for wave propagation between sensors fast high frequency and slow low frequency signals propagating vertically from the surface to the bottom are found for the vertical and horizontal components of the wave motion which are identified with p and s waves respectively the fastest s wave polarized in the east northeast west southwest direction is about 1 9 faster than the slowest s wave polarized in the northwest southeast direction the direction of polarization

virtual source applications to imaging and reservoir monitoring the virtual source method is a breakthrough that allows us to image and monitor the subsurface in cases where surface seismic or vsp fail to deliver in settings where the overburden is complex or changing traditional time lapse signals are weak or nonrepeatable leading to ineffective seismic input to reservoir modeling and little of value generated by repeated seismic surveys on the other hand the virtual source method allows us to image under complex overburden yields repeatable data for reservoir monitoring enables shear seismic and may help us look ahead as we drill

elastic wavefield interferometry using p wave source vsps at the wamsutter field wyoming in this study elastic wavefield interferometry was used to recover p and s waves from the 3d p wave vibrator vsp data at wamsutter field in wyoming s wave velocity and birefringence is of particular interest for the geophysical objectives of lithology discrimination and fracture characterization in naturally fractured tight gas sand reservoirs because we rely on deconvolution interferometry for retrieving interreceiver p and s waves in the subsurface the output fields are suitable for high resolution local reservoir characterization in 1d media where the borehole is nearly vertical data at the stationary phase point is not conducive to conventional interferometry strong tube wave noise generated by physical sources near the borehole interfere with s wave splitting analyses also converted p to s wave ps wave polarity reversals occur at zero offset and cancel their recovery we developed methods to eliminate tube wave noise by removing physical sources at the stationary phase point and pertur

extracting earth s elastic wave response from noise measurements recent research has shown that noise can be turned from a nuisance into a useful seismic source in seismology and other fields in science and engineering the estimation of the system response from noise measurements has proven to be a powerful technique to convey the essence of the method we first treat the simplest case of a homogeneous medium to show how noise measurements can be used to estimate waves that propagate between sensors we provide an overview of physics research dating back more than 100 years showing that random field fluctuations contain information about the system response this principle has found extensive use in surface wave seismology but can also be applied to the estimation of body waves because noise provides continuous illumination of the subsurface the extracted response is ideally suited for time lapse monitoring we present examples of time lapse monitoring as applied to the softening of soil after the 2011 tohoku oki earthquake the detection of a precursor to a landslide and temporal changes in the lunar soil

rhenium and osmium isotopes in black shales and ni mo pge rich sulfide layers yukon territory canada and hunan and guizhou provinces china rhenium and osmium abundances and osmium isotopic compositions were determined by negative thermal ionization mass spectrometry for samples of devonian black shale and an associated ni enriched sulfide layer from the yukon territory canada the same composition information was also obtained for samples of early cambrian ni mo rich sulfide layers hosted in black shale in guizhou and hunan provinces china this study was undertaken to constrain the origin of the pge enrichment in the sulfide layers samples of the ni sulfide layer from the yukon territory are highly enriched in re os and other pge with distinctly higher re 192os but similar pt re compared to the black shale host re os isotopic data of the black shale and the sulfide layer are approximately isochronous and the data plot close to reference isochrons which bracket the depositional age of the enclosing shales samples of the chinese sulfide layers are also highly enriched in re os and the other pge re 192os are lower than in the yukon sulfide layer re os isotopic data for the sulfide layers lie near a reference isochron with an age of 560 ma similar to the depositional age of the black shale host the osmium isotopic data suggest that re and pge enrichment of the brecciated sulfide layers in both the yukon territory and in southern china may have occurred near the time of sediment deposition or during early diagenesis during the middle to late devonian and early cambrian respectively

generalised receiver functions and seismic interferometry abstract classical seismological receiver functions are correlational or deconvolutional combinations of vertical and horizontal component seismometer recordings of earthquake waves that focus information on near receiver subsurface earth structure and properties we show that seismic interferometry can be thought of as a generalisation of receiver functions analysis to cases where recordings at pairs of receivers are considered simultaneously and where either the same or different component recordings are combined further seismic interferometry uses any of deconvolution convolution and cross correlation and energy from either impulsive or random noise sources we show both how receiver functions can logically be extended to a new convolutional form and that the now little used correlational form of receiver functions contains more intuitive information than previously realised seismic interferometry has provided other extraordinary extensions to seismologists arsenal passive noise recordings can be converted into seismograms from virtual imagined earthquakes that in turn can be used to image the real earth active sources e g earthquakes or man made sources can be redatumed into new virtual sources elsewhere or can be converted into virtual sensors seismometers that record seismograms from other real earthquakes man made sources or noise sources that occur either in the future or in the past and the ability to construct virtual sources and sensors at desired times and locations rather than having to wait for earthquake sources that occur at uncontrollable locations promises more repeatable monitoring of changes in earth subsurface properties over time indeed so called coda wave interferometry offers unprecedented accuracy in detecting such changes finally existing theoretical extensions to other regimes such as electromagnetic electrokinetic and diffusive energy propagation may lead to future revolutions in other domains of science

seismic interferometry by tangent phase correction we present a modified interferometry method based on local tangent phase analysis which corrects the cross correlated data before summation the approach makes it possible to synthesize virtual signals usually vanishing in the conventional seismic interferometry summation for a given pair of receivers and a set of different source positions a plurality of virtual traces is obtained at new stationary projected points located along the signal wavefronts passing through the real reference receiver the position of the projected points is estimated by minimizing travel times using wavefront constraint and correlation signal tangent information the method uses mixed processing which is partially based on velocity model knowledge and on data based blind interferometry the approach can be used for selected events including reflections with different stationary conditions and projected points with respect to those of the direct arrivals to extend the interferometry representation in seismic exploration data where conventional illumination coverage is not sufficient to obtain the stationary phase condition we discuss possible applications in crosswell geometry with a velocity anomaly and a time lapse

application of virtual source technology to the zuidwending gas storage project the gasunie nuon underground gas storage consortium plans to drill and leach caverns in the zuidwending salt dome in the netherlands according to safety regulations gas storage caverns must be at least 150 m from the salt flank the location of the zuidwending salt flank however was not well known its uncertainty based on surface seismic is some 200 m figure 1 a more precise estimate of the salt flank location was needed for the project to proceed

insights into subtropical australian aridity from welsby lagoon north stradbroke island over the past 80 000 years abstract terrestrial sedimentary archives that record environmental responses to climate over the last glacial cycle are underrepresented in subtropical australia limited spatial and temporal palaeoenvironmental record coverage across large parts of eastern australia contribute to uncertainty regarding the relationship between long term climate change and palaeoecological turnover including the extinction of australian megafauna during the late pleistocene this study presents a new high resolution calibrated geochemical record and numerical dating framework from welsby lagoon a wetland from north stradbroke island that records key periods of late pleistocene environmental change single grain optically stimulated luminescence and radiocarbon dating are integrated into a bayesian age depth model for the sedimentary sequence spanning marine isotope stage mis 5 to the present scanning micro x ray fluorescence xrf and bulk sediment xrf assays are used to infer past dust dynamics with changes in the abundance of silica and potassium interpreted as proxies for aridity across local and regional sources variations in dust flux were contemporaneous with hydrological change concordant with changes in vegetation cover on the island and relate to deflation events at major dust source regions on the australian continent the welsby lagoon record supports the notion of a variable mis4 within which an increased dust flux 71 67 ka may be indicative of drier climate additionally the record also shows a lower dust flux through the last glacial maximum lgm than is evident in other australian aeolian records however this low lgm flux is attributed to the wetland s evolution rather than a reduction in total dust flux

on the relation between seismic interferometry and the simultaneous source method summary in seismic interferometry the response to a virtual source is created from responses to sequential transient or simultaneous noise sources in the simultaneous source method overlapping responses to sources with small time delays are recorded seismic interferometry and the simultaneous source method are related in this paper we make this relation explicit by discussing deblending as a form of seismic interferometry by multidimensional deconvolution

trace and rare earth element geochemistry of black shale and kerogen in the early cambrian niutitang formation in guizhou province south china constraints for redox environments and origin of metal enrichments abstract early cambrian black shales of south china not only host important sponge arthropod and other soft bodied fossils that have helped to trace early metazoan diversification but also show extreme enrichments of a number of trace metals in particular ni mo and v in this study we use a new approach by analyzing rare earth elements in kerogen extracted from the black shales together with a number of redox sensitive trace element compositions and total organic carbon toc concentrations in an early cambrian black shale sequence in zunyi guizhou province south china to place better constraints on the oceanic redox conditions and the origin of the extreme metal enrichment our data show significant negative ce anomalies ce ce as low as 0 4 occurring in kerogen which indicate an oxygenated surface environment of primary productivity in consistent with the concept that the organic matter is mainly derived from organisms in the euphotic zone mass balance calculation suggests that the kerogen associated ree can dominate the measured black shale ree budget while similarity between our measured ree patterns and those of similarly aged phosphorites indicates that the ree content of ancient phosphorites may have also derived initially from organic matter the redox sensitive trace elements such as u v mo and their ratios of u al v al and mo al in black shales show different correlation patterns with toc contents the upper black shales show a good metal toc correlation but such a correlation is absent in the lower part the lower black shales exhibit much higher metal enrichments compared to black sea sulphidic euxinic sediment this is taken to indicate the presence of sulphidic bottom waters during the deposition of the lower black shales including the ni mo ore layer in contrast anoxic non sulphidic conditions occurred during the deposition of the upper black shales taking all these geochemical data together we suggest that the early cambrian south china seaway was strongly stratified and stagnant and that euxinic bottom water conditions may have led to enrichment of the redox sensitive metals such as u v and mo in the lower black shales and in one case the occurrence of a polymetallic ni mo sulphide ore bed bearing an extraordinarily extreme metal enrichment which according to the mo toc and ni toc ratios and much other geochemical evidence may have been additionally influenced by hydrothermal input of metals within the rift basin as suggested by a number of previous studies

redatuming through a salt canopy and target oriented salt flank imaging we describe a new shortcut strategy for imaging the sediments and salt edge around a salt flank through an overburden salt canopy we tested its performance and capabilities on 2d synthetic acoustic seismic data from a gulf of mexico style model we first redatumed surface shots using seismic interferometry from a walkaway vertical seismic profile survey as if the source and receiver pairs had been located in the borehole at the positions of the receivers this process creates effective downhole shot gathers by completely moving surface shots through the salt canopy without any knowledge of overburden velocity structure after redatuming we can apply multiple passes of prestack migration from the reference datum of the bore hole in our example first pass migration using only a simple vertical velocity gradient model reveals the outline of the salt edge a second pass of reverse time prestack depth migration using full two way wave equation was performed with an updated velocity model that consisted of the velocity gradient and salt dome the second pass migration brings out dipping sediments abutting the salt flank because these reflectors were illuminated by energy that bounced off the salt flank forming prismatic reflections in this target oriented strategy the computationally fast redatuming process eliminates the need for the traditional complex process of velocity estimation model building and iterative depth migration to remove effects of the salt canopy and surrounding overburden this might allow this strategy to be used in the field in near real time