ultrasonic velocity and attenuation during co2 injection into water saturated porous sandstone measurements using difference seismic tomography we undertook laboratory based seismic measurements with dense sensor array at ultrasonic frequencies during the injection of co2 into a water saturated sandstone specimen the resulting high quality seismic data enabled detailed determination of the relative velocity and attenuation coefficient of the compressional wave using difference seismic tomography which directly inverses time lapse changes in rock properties from time lapse changes in observed data co2 migration and water displacement were clearly mapped using tomographic images of relative velocity and the attenuation coefficient the final and largely stabilised volume fraction of co2 in the pore space of the sample is about 30 40 on average the p velocity fell by 7 5 12 and 14 5 and the attenuation coefficient q 1 increased by factors of 3 3 2 7 and 3 7 as a result of the replacement of water with co2 during the injection of gaseous liquid and supercritical co2 respectively as a function of gas saturation both the velocity and attenuation data are in good agreement with results obtained using the white and dutta ode model for partial saturation indicating that viscous losses due to fluid diffusion are of significant importance for compressional waves travelling at ultrasonic frequencies in porous rocks

postmap migration of crosswell reflection seismic data vertical seismic profiling common depth point vsp cdp mapping is often preferred to crosswell migration when imaging crosswell seismic reflection data the principal advantage of vsp cdp mapping is that it can be configured as a one to one operation between data in the acquisition domain and data in the image domain and therefore does not smear coherent noise such as tube waves guided waves and converted waves as crosswell migration could however unlike crosswell migration vsp cdp mapping cannot collapse diffractions therefore the lateral resolution of reflection events suffers we present a migration algorithm that is applied to the crosswell data after they have been mapped by performing crosswell migration in two distinct steps mapping followed by diffraction stacking noise events can be identified and filtered in the mapped domain without smearing effects commonly associated with conventional crosswell migration operators tests on noise free synthetic crosswell data indicate that the two ste

fermat s interferometric principle for target oriented traveltime tomography an interferometric form of fermat s principle is derived that allows for high resolution estimation of the velocity distribution between deep interfaces the data consist of reflection traveltimes from two deeply buried interfaces a and b recorded by sources and caused by receivers at the surface fermat s interferometric principle is then used to kinematically redatum the surface sources and receivers to interface a so that the associated reflection times correspond to localized transit times between the a and b interfaces the velocity model above interface a does not need to be known so the distorting effects of the overburden and statics are eliminated by this target oriented approach interferometric target oriented tomography promises to enhance the resolution of whole earth and exploration tomograms

high resolution crosswell imaging of a west texas carbonate reservoir part 1 project summary and interpretation a carbon dioxide flood pilot is being conducted in a section of chevron s mcelroy field in crane county west texas prior to co2 injection two high frequency crosswell seismic profiles were recorded to investigate the use of seismic profiling for high resolution reservoir delineation and co2 monitoring these preinjection profiles provide the baseline for time lapse monitoring profile 1 was recorded between an injector well and an offset observation well at a nominal well to well distance of 184 ft 56 m profile 2 was recorded between a producing well and the observation well at a nominal distance of 600 ft 183 m the combination of traveltime tomography and stacked cdp reflection amplitudes demonstrates how high frequency crosswell seismic data can be used to image both large and small scale heterogeneity between wells transmission traveltime tomography is used to image the large scale velocity variations cdp reflection imaging is then used to image smaller scale impedance heterogeneities the

orbitally driven insolation forcing on holocene climate trends evidence from alkenone data and climate modeling a global spatial pattern of long term sea surface temperature sst trends over the last 7000 years is explored using a comparison of alkenone derived sst records with transient ensemble climate simulations with a coupled atmosphere ocean circulation model under orbitally driven insolation forcing the spatial trend pattern both in paleo sst data and in model results shows pronounced global heterogeneity generally the extratropics cooled while the tropics experienced a warming during the middle to late holocene we attribute these divergent holocene climate trends to seasonally opposing insolation changes furthermore climate mode changes similar to the arctic north atlantic oscillation are superimposed on the prevalent pattern it is concluded that nonlinear changes in the entire seasonal cycle of insolation played a dominant role for the temporal evolution of holocene surface temperatures for understanding of marine proxy data apart from the dominance of summer insolation in high latitudes a notable shift in the maximum insolation of the year in low latitudes has to be taken into account which may influence timing of phytoplankton production and thus alters the seasonal origin of temperature signals recorded in the proxies

plio pleistocene palaeogeography of the southern north sea basin 3 75 0 60 ma abstract palaeogeographical maps are presented for the southern north sea basin from approximately 1 w to 7 e and 51 55 n for the period from approximately 3 75 0 60 ma reconstructions centre on 3 75 ma coralline cragbrunssumian 2 55 ma red crag brielle ground reuverian 2 40 ma red crag westkapelle ground praetiglian early tiglian 2 00 ma norwich crag smith s knoll and ijmuiden ground middle tiglian 1 75 1 70 ma cromer forest bed paston winterton shoal late tiglian eburonian 1 40 ma kesgrave yarmouth roads waalian 1 15 ma kesgrave yarmouth roads menapian and 0 60 ma cromer forest bed west runton yarmouth roads cromerian complex from 3 75 2 40 ma the basin is mainly a marine area fringed to the east and south by fluviatile deposition and broadly open via the southwest to the atlantic following marked marine regression and cooling at around 2 40 ma the period from 2 00 1 70 ma is mainly one of renewed marine transgression and warmer conditions during which a great european delta built out fed mainly from the east and south into the southern north sea from 1 40 0 60 ma marine waters were almost entirely excluded from the area and temperate intervals alternated with increasingly glacial episodes whilst the great european delta continued to expand northwards into the northern north sea

bio and chronostratigraphy of the lateglacial in the eifel region germany abstract in recent years enormous success has been achieved in varve counting of the eifel maar lakes but a detailed correlation with the biostratigraphy has been missing in this paper we present new palynological results of the lateglacial sequences from holzmaar lake and meerfelder maar lake based on annually laminated sediments in particular the meerfelder maar has great potential because in contrast to the holzmaar the sequence between the ulmener maar tephra 11 000 varve years bp and the laacher see tephra 12 880 varve years bp including the younger dryas is undisturbed and complete therefore we currently use the meerfelder maar chronology brauer et al 1999b as an independent varve calendar for the biostratigraphy of the lateglacial the palynological signals of both maar lakes are in good agreement and can easily be correlated with one another and with type sections type regions in northwestern germany and jutland the sequences of the eifel maar lakes have the quality of hypostratotypes with regional biozones based on an absolute time scale

doomed pioneers gravity flow deposition and bioturbation in marine oxygen deficient environments isolated horizons of thalassinoides and gyrolithes burrows appear in exclusive association with gravity flow deposits within sequences of nonbioturbated hernipelagic sedimentary rocks of the miocene monterey formation of california and the oligocene miocene san gregorio formation of baja california these burrowed levels are not associated with other ichnogenera such as zoophycos and chondrites we infer a causal relation between gravity flow deposition and the presence of thalassinoides and gyrolithes and suggest that these gravity flows entrained thalassinidean crustacea upon deposition in oxygen deficient environments the surviving borrowers reworked substantial quantities of aminated commonly organic rich sediments in an environment from which they were previously excluded the persistence of or the ecologically rapid return to oxygen depleted conditions limited the survival time and ecological complexity of the transported infaunal dwellers and rendered them doomed pioneers ecological and physiological data support this hypothesis thalassinidean crustacea have the capability to endure turbulent transport and survive up to 5 7 days of anoxia without being severely limited in their biological activities the accurate recognition of doomed pioneer trace fossil assemblages as ephemeral ecological phenomena in otherwise laminated successions may contribute to a better understanding and interpretation of paleo oxygen levels and basin history

crosswell seismic imaging for deep gas reservoir characterization a gas discovery in the shengping area of the daqing oilfield in china was made recently in a large scale volcanic depositional environment because gas in the heterogeneities of formations broken by tectonic activity and localized volcanic eruptions is not common researchers sought a more detailed reservoir characterization before developing the field crosswell seismic data were used to augment existing 3d surface seismic log and core data this provided data at five times the resolution of the surface seismic data to bridge the gap in resolution between surface seismic and well data crosswell seismic data were acquired in two wells 832 m apart and processed to provide images of reflectivity velocity and formation properties from sections produced by amplitude versus angle ava inversion the state of the art in crosswell seismic is summarized briefly reviewing progress in data acquisition and data processing over several decades of crosswell technology development a detailed description of th

nonlinear 3 d traveltime inversion of crosshole data with an application in the area of the middle ural mountains this paper deals with the problem of nonlinear seismic velocity estimation from first arrival traveltimes obtained from crosshole and downhole experiments in three dimensions a standard tomographic procedure is applied based on the representation of the crosshole area into a number of cells which have an initial slowness assigned for the forward modeling the raypath matrix is computed using the revisited ray bending method supplemented by an approximate computation of the first fresnel zone at each point of the ray hence using physical and not only mathematical rays since 3 d ray tracing is incorporated the inversion technique is nonlinear velocity images are obtained by a constrained least squares inversion scheme using both damping and smoothing factors the appropriate choice of these factors is defined by the use of appropriate criteria such as the l curve the tomographic approach is improved by incorporating a priori information about the media to be imaged into our inversion scheme th

pseudoplanktonic and benthic invertebrates in the middle jurassic opalinum clay northern switzerland abstract a high resolution study of the opalinum clay of northern switzerland confirmed the hypothesis of wignall and simms 1990 that pseudoplankton is exceedingly rare in the fossil record and that even in dark organic rich mudstones and black shales it constitutes only a minor proportion of the fauna in the opalinum clay only a bryozoan one lepadomorph barnacle and inarticulate brachiopods and oysters attached to ammonite shells represent the pseudoplankton the life style of the posidoniid bivalve bositra buchi is re evaluated based on the bell shaped abundance distribution along an oxygenation gradient and nearest neighbor spatial analysis it appears that this species was truly benthic and probably byssally attached to the substrate previous suggestions of a chemosymbiotic mode of life for this bivalve are dismissed rather this bivalve was an erratic opportunist capable of rapidly colonizing a variety of fine grained sediments and reached its peak abundances in severely oxygen depleted palaeo environments a benthic mode of life is also proposed for the inoceramid pseudomytiloides dubius which however is also known to occur as facultative pseudoplankton evidence regarding the mode of life of the small gastropod coelodiscus sp is not conclusive but suggests a benthic life style

quaternary geology of eastern germany saxony saxon anhalt south brandenburg thuringia type area of the elsterian and saalian stages in europe abstract the characteristic feature of the quaternary geology of eastern germany location map fig 1 is a sequence of more than 50 horizons and complexes of glacial laminated clays tills glaciofluvial sediments and periglacial river gravels gelifluction sheets alluvium loess facies in the period between the younger tertiary and the first elsterian continental glaciation at least four gravel terraces were built up under cold climate conditions the youngest of these gravel bodies lacks scandinavian rocks and is interbedded with elsterian glaciolacustrine deposits pre elsterian temperate periods have been recorded at a number of places i e zeuchfeld untermassfeld voigtstedt sussenborn two major ice advances with additional minor oscillations have been identified of elsterian and saalian ages complete eemian and holsteinian sequences are represented showing vegetational development through each interglacial cycle cool temperate warm cool the weichselian glacial stage in eastern germany is represented by thick periglacial sedimentation including gravels gelifluction sheets alluvium debris covers and loess within these sediments is a wide variety of glaciotectonic structures and periglacial soil structures including classical involutions and ice wedge casts an outline of the present state of knowledge of the quaternary of eastern germany is given in tables 1 3 while table 4 presents a stratigraphical comparison with the neighbouring regions and countries the palaeogeography of the region during the periods of the european continental glaciation is depicted in fig 2

target oriented interferometric tomography for gpr data an interferometric form of fermat s principle and traveltime tomography is used to invert ground penetrating radar gpr data for the subsurface velocity distribution the input data consist of gpr traveltimes of reflections from two buried interfaces a reference and b target where the data are excited and recorded by gpr antennas at the surface fermat s interferometric principle is then used to redatum the surface transmitters and receivers to interface a so the associated reflection traveltimes correspond to localized transit times between interfaces a and b the overburden velocity model above interface a is not required the result after tomographic inversion is a high resolution estimate of the velocity between interfaces a and b that does not depend on the velocity model above interface a a motivation for introducing interferometric traveltime tomography is that typical layer stripping approaches will see the slowness error increase with depth as the layers are inverted this suggests that

raised beaches and sea levels in the english channel in the middle and late pleistocene problems of interpretation and implications for the isolation of the british isles

high resolution crosswell imaging of a west texas carbonate reservoir part 5 core analysis we conducted a core analysis program to provide supporting data to a series of crosswell field experiments being carried out in mcelroy field by stanford university s seismic tomography project the objective of these experiments is to demonstrate the use of crosswell seismic profiling for reservoir characterization and for monitoring co2 flooding for these west texas carbonates we estimate that co2 saturation causes p wave velocity to change by 1 9 pooled average range 6 3 to 0 1 s wave velocity by 0 6 range 0 to 2 7 and the p to s velocity ratio by 2 4 range 6 4 to 0 3 when we compare these results to the precisions we can expect from traveltime tomography about 1 for p and s wave velocity and about 2 for the p to s velocity ratio we conclude that time lapse traveltime tomography is sensitive enough to resolve changes in the p wave velocity s wave velocity and p to s velocity ratio that result from co2 saturation we concentrated here on the potential for co2 sat

phase relationship and surface water mass change in the northeast atlantic during marine isotope stage 11 mis 11 planktic foraminiferal census data faunal sea surface temperatures ssts and oxygen isotopic and lithic records from a site in the northeast atlantic were analyzed to study the interglacial dynamics of marine isotope stage mis 11 a period thought to closely resemble the holocene on the basis of orbital forcing interglacial conditions during mis 11 persisted for approximately 26 ka after the main deglacial meltwater processes ceased a 10 to 12 ka long transitional period marked by significant water mass circulation changes occurred before surface waters finally reached their thermal maximum this sst peak occurred between 400 and 397 ka inferred from the abundance of the most thermophilic foraminiferal species and was coincident with lowest sea level according to benthic isotope values the ensuing stepwise sst decrease characterizes the overall climate deterioration preceding the increase in global ice volume by 3 ka this cooling trend was followed by a more pronounced cold event that began at 388 ka and that terminated in the recurrence of icebergs at the site around 382 ka because the water mass configuration of early mis 11 evolved quite differently from that of the early holocene there is little evidence that mis 11 can serve as an appropriate analogue for a future holocene climate despite the similarity in some orbital parameters

pressure and temperature dependence of acoustic wave speeds in bitumen saturated carbonates implications for seismic monitoring of the grosmont formation abstractrecent time lapse seismic observations in carbonate reservoirs subject to steam assisted enhanced oil recovery display substantial changes in seismic reflectivity due to the combined effects of saturation pressure and temperature understanding these field seismic observations requires knowledge of the effects on the seismic wave speeds in bitumen saturated carbonates we have conducted ultrasonic measurements of p and s wave velocities in bitumen saturated dolomite taken from the grosmont formation in northern alberta wave speeds are measured under a variety of conditions of constant pore pressure constant effective pressure and with varying temperature to map the various controlling factors the temperature dependent declines of 12 and 9 for the p and s wave speeds respectively with temperatures from 10 c to 102 c are most notable unlike oil sands at times the dolomite retains its structure upon removal of the bitumen allowing for measurement of the dry and water saturated frame pr

late quaternary expansion of norway spruce picea abies l karst in europe according to pollen data abstract lateglacial and holocene expansion of norway spruce picea abies l karst in europe is reconstructed in steps of 1000 radiocarbon years on the basis of pollen data collected from literature and databases pollen thresholds for the lateglacial of 0 1 2 5 and 10 and for the holocene of 2 were used spruce pollen representation and limitations of pollen data are discussed we assume that the 2 threshold tracks the advance of the main spruce front but might fail to detect small populations or those present in low density the history of spruce expansion was distinctly different in northern and southern parts of its range 1 in ne europe spruce expanded during the allerod reaching southwards to n byelorussia during the younger dryas spruce populations contracted north of ca 60 n but expanded strongly in the region approximately 53 60 n 23 32 e where they declined at the beginning of the holocene we infer that the lateglacial expansion in ne europe concerned mainly p abies subsp obovata 2 holocene expansion in n europe concerned mainly p abies subsp abies southward expansion within the northern range is continuing to the recent millennium 3 in central europe spruce expanded vigorously during the allerod contracted or stagnated during the younger dryas and then strongly re expanded during the preboreal following the simple expectation that climatic warming had a positive impact on its development 4 holocene westward and northward expansion of spruce in its southern range central europe was rapid 10 8 ka 14 c bp very slow 8 6 ka 14 c bp and rapid 6 5 ka 14 c bp when the present day western limits were reached 5 the 2 spruce pollen threshold is too high to detect the fact that the northern and southern ranges of spruce have joined in the holocene the persistence of low spruce abundance in the transitional area is explained mainly by the strong anthropogenic deforestation ever since spruce grew there

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

crosswell seismic imaging in a contaminated basalt aquifer multiple seismic crosswell surveys have been acquired and analyzed in a fractured basalt aquifer at idaho national engineering and environmental laboratory most of these surveys used a high frequency 1000 10 000 hz piezoelectric seismic source to obtain p wave velocity tomograms the p wave velocities range from less than 3200 m s to more than 5000 m s additionally a new type of borehole seismic source was deployed as part of the subsurface characterization program at this contaminated groundwater site this source known as an orbital vibrator allows simultaneous acquisition of p and s waves at frequencies of 100 to 400 hz and acquisition over larger distances the velocity tomograms show a relationship to contaminant transport in the groundwater zones of high contaminant concentration are coincident with zones of low velocity and high attenuation and are interpreted to be fracture zones at the boundaries between basalt flows the orbital vibrator data show high vp vs values from 1 8 to 2 8 in

pollen analytical biostratigraphy of the last five climatic cycles from a long continental sequence from the velay region massif central france in the volcanic region of velay massif central france lake sediment sequences derived from maar craters situated close to one another ribains praclaux and lac du bouchet have been correlated on the basis of tephrostratigraphical analyses this has enabled the construction of a sequence 2980 pollen spectra that begins during the glaciation preceding the holsteinian and ends in the present this sequence covers the period from 450 ka i e from the end of marine oxygen isotope stage 12 to the present time and includes five climatic cycles the study of a second core from the praclaux site completed the long velay sequence the biostratigraphy of the whole sequence is described in detail and illustrated by a synthetic and simplified pollen diagram thirteen temperate forest episodes interglacials or interstadials and as many cold periods glacials or stadials are defined each temperate episode is characterised by particular forest development and vegetation dynamics and all of them with the exception of the holocene begin and end with a pinus forest the vegetation dynamics observed during the holocene resemble more closely those recorded during the interstadials than during the interglacials copyright 2000 john wiley sons ltd

sequence stratigraphy of a tidally dominated carbonate siliciclastic ramp the tithonian early berriasian of the southern neuquen basin argentina the tithonian berriasian vaca muerta carrin cura and picun leufu formations in the southern neuquen basin were deposited on a tidally dominated mixed carbonate siliciclastic ramp basinal outer middle shallow and back ramp facies associations are recognized and a sequence stratigraphic analysis reveals that the ramp record consists of three shallowing upwards sequences ti1 ti2 and ti3 set within a lower order progradational cycle a higher order of cyclicity is superimposed on to the middle ti2 sequence the majority of the ramp facies belong to the transgressive and highstand systems tracts however at the base of ti2 a lowstand systems tract is identified characterized by a basal unconformity and an abrupt basinward shift of the shallow marine lithofacies transgressive systems tracts were characterized by slow sedimentation rates and rapid sea level rises that affected carbonate productivity highstand systems tracts show the greatest carbonate productivity and an increased progradation rate on account of a reduction in accommodation space generation palaeogeography played a major role in the development of the depositional systems partial isolation from the pacific ocean reflecting the growth of the andean magmatic arc and geographic restriction due to tectonic inversion in the central part of the basin resulted in a meso macrotidal regime that produced a tidally dominated sedimentary record in the shallow and back ramp environments coeval anoxic conditions in the central part of the neuquen basin favoured distal ramp and basinal black shale deposition during episodes of relative sea level rise

carbonate ramp depositional systems abstract the classification tectonic settings stratigraphy and early diagenesis of carbonate ramp systems are reviewed carbonate ramps are common in all geological periods but were dominant at times when reef constructing organisms were absent or inhibited ramps can be subdivided into inner mid and outer ramp environments the mid ramp zone extends from fair weather wave base to normal storm wave base although the water depths which these boundaries represent vary an additional outer slope environment occurs on distally steepened ramps as with siliciclastic shelves a range of wave storm and tide dominated ramps can be recognised and this forms the most convenient basis for ramp classification the carbonate productivity profile of ramps differs from that of rimmed shelves with the inner ramp showing lower production rates than comparable shallow water facies on rimmed shelves the zone of greatest organic carbonate sediment production appears to have shifted from the mid ramp to the inner ramp since the late jurassic carbonate ramps occur in most types of sedimentary basin but are best developed where subsidence is flexural and gradients are slight over large areas as in foreland and cratonic interior basins and along passive margins the featureless depositional profiles of many ramps means that sequence geometries are best observed on regional seismic lines some show low angle sigmoidal or shingled clinoforms suggesting that ramps may seldom be homoclinal but possess subtle slope geometries which reflect depositional environments because of their low angle slopes ramps respond differently to rimmed shelves during relative sea level changes although results seem to be strongly dependent on the rate of relative sea level change during a minor fall shallow ramp facies belts will simply shift basinwards in a forced regression in contrast the whole surface of a steep sloped flat topped rimmed shelf may be exposed so that sediment production ceases or is drastically reduced during a major fall shallow ramp bounded basins may empty completely conversely ramps also flood gradually whereas rimmed shelves do so more rapidly homoclinal ramps develop no resedimented lowstand deposits rimmed shelves and distally steepened ramps in contrast may develop lowstand talus or turbiditic wedges distally steepened ramps may behave more like homoclinal ramps during minor base level falls and like rimmed shelves during major base level falls many ramps consist of layered successions of several ramp sequences stacked one upon the other ramp stacks of this sort may show gross vertical accretion but individual ramp sequences seldom appear to develop in a keep up style apart from minor organic buildups as with many rimmed shelves steepening of the outer ramp margin due to tectonism slope inheritance or differential sedimentation may promote the development of a distally steepened ramp or rimmed shelf a wide variety of organisms have constructed buildups in mid and outer ramp environments isolated buildups may seed early in ramp development accrete to wave base or sea level and continue growth by stacking through successive ramp sequences so that depositional and diagenetic features within them are in concert with those of the shallow ramp the location of isolated buildups on ramps is governed by tectonism halokinesis antecedent topography or by the subtle slope geometry of the previous ramp sequence diagenesis on ramps shows some major variations compared with diagenesis on steep sloped flat topped carbonate platforms ramp bounded basins may form prolific petroleum sourcing and reservoiring systems and offer a range of subtle stratigraphic play types and lateral facies variations which determine reservoir quality and distribution isolated buildups in the mid and outer ramp environments represent one of the commonest petroleum reservoirs in ramp systems and tend to have their foundations in transgressive systems tracts grainstone and packstone reservoirs are widespread and range from shoreline carbonate sandbodies to major detached shoal complexes or shoals over offshore highs grainstone sandbodies occur in both highstand systems tracts and in prograding lowstand wedges

carbonate rocks and petroleum reservoirs a geological perspective from the industry abstract carbonate oil reservoirs are sometimes regarded with apprehension in the petroleum industry since it can be difficult to predict the quality of and ensure high recovery factors from this rock family particular problems are the complex and heterogeneous nature of porosity in carbonate rocks often leading to large ranges in permeability for any given porosity and the organization of carbonate successions most commonly as vertically heterogeneous but laterally persistent layers important issues that arise time and again in carbonate reservoir description include a predicting reservoir quality at inter well scales and in uncored wells b recognizing problematic high permeability layers c determining the permeability component to allocate to fractures and connected vug systems and d populating reservoir models with representative physical parameters because porosity in carbonate rocks generally presents as diverse and heterogeneous conventional core plugs are seldom representative of large rock volumes and significant issues remain in terms of the scale compatibility of the various datasets for measured physical parameters that are used in carbonate reservoir description many of the world9s largest carbonate reservoirs were discovered and developed shortly after the second world war and are now showing signs of maturity expressed variously as poor pressure support water or gas breakthrough and stranded resources the proportion of the world9s conventional petroleum that is reservoired in carbonate rocks is commonly estimated at around 50 60 and many large carbonate reservoirs are likely to have a production lifetime beyond 50 years it is no coincidence then that the petroleum industry has been the primary source of funding of and promotion of research into carbonate rocks and depositional systems often with impacts extending well beyond oil and gas exploitation

improved seismic image by q compensated reverse time migration application to crosswell field data west texas abstractto test the effectiveness of the q compensated reverse time migration q rtm method we applied it to crosswell seismic data from western texas this crosswell field survey was aimed at determining the boundaries and even the internal features of the reservoir in this area the reservoir geologic body exhibits strong attenuation that reduces high frequencies more rapidly thus conventional acoustic rtm produces a dimmed image reduced amplitude and low resolution of the reservoir area and structures underneath in contrast q rtm is able to compensate for the attenuation effects during imaging the vp and qp profiles needed for q rtm were produced by joint traveltime and frequency shift tomography preprocessing of the data was carried out to reduce noise remove tube waves and to separate up and downgoing wavefields along with recovered high wavenumbers the final q rtm image provided many details about geologic layers and structures the lateral and vertical extent and internal structures

ocean climate variability in the eastern north atlantic during interglacial marine isotope stage 11 a partial analogue to the holocene similar orbital geometry and greenhouse gas concentrations during marine isotope stage 11 mis 11 and the holocene make stage 11 perhaps the best geological analogue period for the natural development of the present interglacial climate results of a detailed study of core md01 2443 from the iberian margin suggest that sea surface conditions during stage 11 were not significantly different from those observed during the elapsed portion of the holocene peak interglacial conditions during stage 11 lasted nearly 18 kyr indicating a holocene unperturbed by human activity might last an additional 6 7 kyr a comparison of sea surface temperatures sst derived from planktonic foraminifera for all interglacial intervals of the last million years reveals that warm temperatures during peak interglacials mis 1 5e and 11 were higher on the iberian margin than during substage 7e and most of 9e the sst results are supported by heavier delta 18 o values particularly during 7e indicating colder ssts and a larger residual ice volume benthic delta 13 c results provide evidence of a strong influence of north atlantic deep water at greater depths than present during mis 11 the progressive ocean climate deterioration into the following glaciation is associated with an increase in local upwelling intensity interspersed by periodic cold episodes due to ice rafting events occurring in the north atlantic

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

earthquake induced soft sediment deformation structures in upper jurassic open marine microbialites neuquen basin argentina penecontemporaneous decimetre scale soft sediment deformation structures are reported from the basal part of the upper jurassic lower cretaceous vaca muerta formation in the malargue las lenas area of the back arc neuquen basin mendoza province central andes the deformed interval amarillas bed is only 0 3 to 0 9 m thick but occurs in a wide area larger than 1500 km2 its age determined by ammonite biostratigraphy is early tithonian the soft sediment deformation structures were generated in finely laminated partially consolidated organicrich carbonate microbialites that were deposited in open marine poorly oxygenated settings apparently devoid of any significant slope those structures include boudins of different sizes and complexity a variety of folds normal listric dm scale faults sub horizontal detachment surfaces and other features which are part of several larger scale complex slump structures deformation was dominantly plastic but near to the ductile brittle field transition on the basis of the observed soft deformation structures their geographic distribution their lateral homogeneity and the geodynamic framework of the basin in which it was generated the amarillas bed can be tentatively attributed to a large intermediate depth earthquake that occurred within the plate that subducted beneath the andean continental margin and the neuquen back arc basin

high resolution crosswell imaging of a west texas carbonate reservoir part 2 wavefield modeling and analysis we have collected low noise crosswell data in a high velocity carbonate environment with a spatial sampling interval of 2 5 ft 0 76 m this sampling reveals a variety of coherent events not previously identified in coarsely sampled gathers nearly every event in our field record can be explained using simple approximations for the geology source and receivers without accounting for the presence of the boreholes we have used synthetic records as a guide in a moveout based analysis of the field data our analysis shows that much of the full wavefield energy i e scattered waves in our data are converted modes arising from the direct p and s waves this observation suggests that for crosswell reflection imaging the focus of acquisition and wavefield separation techniques should be on the suppression of once converted modes

varve chronology and palynology of the lateglacial in northwest germany from lacustrine sediments of hamelsee in lower saxony abstract the hamelsee is a dolina from a collapse over permian salt that occurred at the end of the pleniglacial it is more than 21 m deep and contains 18 m of lacustrine sediments the lateglacial sediments in the central part of the lake consist of 2 7 m from 15 to 17 7 m of sapropelic and silty muds which are mostly laminated and partly bioturbated minor slumps occur mainly during colder phases the subdivision of the lateglacial is based on pollen zones multidisciplinary studies of the microfacies from thin sections geochemistry pollen analysis and rotifer analysis allow environmental and palaeoclimatological interpretations to be made the biozones of the lateglacial and their boundaries are marked by rapid climatic changes though covering comparatively short periods of time they are not monotonous but characterized by minor internal climatic fluctuations the sediments of the meiendorf and oldest dryas are not laminated the allerod sediment is seasonally varved without interruption and encompasses 625 yr the eruption of the laacher see volcano 12 900 cal bp had an impact on the climate during the following 10 yr the transition from the allerod to the younger dryas took some 50 yr and it occurred 200 yr after the eruption of the laacher see volcano the abrupt change at the end of the lateglacial 11 560 cal bp occurred within less than 10 yr however many proxies reacted with a time lapse of 15 to 30 yr

pressure and fluid saturation prediction in a multicomponent reservoir using combined seismic and electromagnetic imaging this paper presents a method for combining seismic and electromagnetic em measurements to predict changes in water saturation pressure and co2 gas oil ratio in a reservoir undergoing co2 flood crosswell seismic and em data sets taken before and during co2 flooding of an oil reservoir are inverted to produce crosswell images of the change in compressional velocity shear velocity and electrical conductivity during a co2 injection pilot study a rock properties model is developed using measured log porosity fluid saturations pressure temperature bulk density sonic velocity and electrical conductivity the parameters of the rock properties model are found by an l1 norm simplex minimization of predicted and observed differences in compressional velocity and density a separate minimization using archie s law provides parameters for modeling the relations between water saturation porosity and electrical conductivity the rock properties model is used to generate relationships between changes in

sedimentary history of za hajovnou cave moravia czech republic a unique middle pleistocene palaeontological site za hajovnou cave in the javoricko karst moravia czech republic has a rich record of middle pleistocene typical holsteinian flora and fauna dominated by bear ursus deningeri sedimentological geochemical mineralogical geophysical palynological and zoopalaeontological analyses of the sediments along with u th dating of flowstones place the deposits into a numerical timeframe the cave origin dates to a period before the mid miocene badenian transgression the oldest fluvial deposits are lower pleistocene spanning the brunhes matuyama boundary the later terrestrial deposits range from middle pleistocene to holocene the most important result of u th dating is that the main holsteinian senso lato fossil bed can be correlated with mis 9 the lower fossil bed is probably mis 11 and the upper fossil bed mis 5e this represents one of the still relatively few numerically dated holsteinian sites contradicts the global chronostratigraphical correlation table that places the holsteinian only in mis 11 and supports the concept that the holsteinian is not a single unit and likely not confined to a single interglacial c 2013 elsevier ltd and inqua all rights reserved

high resolution crosswell imaging of a west texas carbonate reservoir part 4 reflection imaging reliable crosswell reflection imaging is a challenging task even after the data have been wavefield separated in the time domain residual strong coherent noise is still present in the data stacking is complicated by the wide range of reflection incidence angles available for imaging with wavelengths of a few feet small misalignments as a result of velocity or geometric errors produce destructive interference and degrade the quality of the stacked image we present an imaging sequence that addressed these complications and allowed us to produce high quality stacked images for both p and s waves from a large volume crosswell data set a very good tie was achieved at both wells heterogeneities imaged from well to well included very thin beds less than 5 ft 1 5 m thick within the reservoir pinchouts and a major angular unconformity the grayburg san andres that could not be observed reliably with any other technique log correlation surface seismic imaging or tomography in fact the produced crosswell reflection images exhibit dramatically higher resolution and continuity than the p wave traveltime tomogram

crosswell traveltime tomography in three dimensions conventional crosswell direct arrival traveltime tomography solves for velocity in a 2 d slice of the subsurface joining two wells many 3 d aspects of real crosswell surveys including well deviations and out of well plane structure are ignored in 2 d models we present a 3 d approach to crosswell tomography that is capable of handling severe well deviations and multiple profile datasets three dimensional pixelized models would be even more seriously underdetermined than the pixelized models that have been used in 2 d tomography we therefore employ a thinly layered vertically discontinuous 3 d velocity model that greatly reduces the number of model parameters the layers are separated by 2 d interfaces represented as 2 d chebyshev polynomials that are determined using a priori structural information and remain fixed in the traveltime inversion the velocity in each layer is also represented as a 2 d chebyshev polynomial unlike pixelized models that provide limited vertical resolution and may be overparameterized horizontally this 3 d model provides vertical resolution comparable to the scale of wireline logs and reduces the degrees of freedom in the horizontal parameterization to the expected in line and out of well plane horizontal resolution available in crosswell traveltime data ray tracing for the nonlinear traveltime inversion is performed in three dimensions the 3 d tomography problem is regularized using penalty constraints with a continuation strategy that allows us to extrapolate the velocity field to a 3 d region containing the 2 d crosswell profile although this velocity field cannot be expected to be accurate throughout the 3 d region it is at least as accurate as 2 d tomograms near the well plane of each 2 d crosswell profile futhermore multiple profile crosswell data can be inverted simultaneously to resolve better the 3 d distribution of velocity near the profiles our velocity parameterization is quite different from pixelized models so resolution properties will be different using wave modeled synthetic data we find that near horizontal raypaths have the largest mismatch between ray traced traveltimes and traveltimes estimated from the data in conventional tomography horizontal raypaths are essential for high vertical resolution with our model however the highest resolution and most accurate inversions are achieved by excluding raypaths that travel nearly parallel to the geologic layering we perform this exclusion in both a static and model based manner we apply our 3 d method to a multiple profile crosswell survey at the cymric oil field in california an area of very steep structural dips and significant well trajectory deviations results of this multiple profile 3 d tomography correlate very well with the independently processed single profile results with the advantage of an improved tie at the common well

eemian and early weichselian temperature and precipitation variability in northern germany abstract dramatic changes in european vegetation occurred during the transition from the eemian interglacial to weichselian glacial climates correlative with major changes in global ice core and marine records quantitative knowledge of climate change is important for understanding of the climate system and for climate modelling for which reconstructions of this transitional period are of special interest however it has been difficult to quantify the climatic changes involved in the eemian to early weichselian transition from terrestrial archives due to the lack of modern vegetation analogues to circumvent this problem we applied a suitable multivariate probabilistic approach to pollen and plant macrofossil assemblages to reconstruct temperature and precipitation for this transition in central europe our reconstructions span the interval from the beginning of the eemian marine isotope stage mis 5e to the odderade interstadial mis 5a they indicate a relatively stable eemian with increasing precipitation reducing the continentality of the climate with time during the transition from the eemian to the herning stadial mean july and january temperatures decreased by 4 c and by as much as 20 c respectively temperatures remained high enough to support forests during the stadials and we infer that the reconstructed decrease of precipitation below 500 mm per year caused the extirpation of forests during these periods thus we conclude that precipitation although difficult to reconstruct is of vital importance for explaining vegetation change during the eemian and eemian early weichselian transition

combined flow model for vertical stratification sequences in shallow marine storm deposited beds abstract we develop a model to help explain the wide variety of vertical stratification sequences in shallow marine sandstones this model embodied in a set of vertical sequence cartoons predicts or accounts for vertical stratification sequences in beds of free sandstone deposited from a full range of decelerating combined flows as well as from purely unidirectional and oscillatory flows according to the model vertical stratification sequences in storm deposited sandstone beds are the outcome of the time history of the bed configuration as deposition proceeds the idealized sequences are based on the initial velocities and subsequent deceleration histories of the unidirectional and oscillatory flow components twenty qualitatively different sequences starting with plane bed are generated and an additional 26 sequences result from omitting one or more of the lowermost intervals in succession the model thus accounts for 46 distinct kinds of sequences five major simplifying assumptions are built into the model bidirectional flows linear deceleration of both unidirectional and oscillatory flow components time independent deposition rate time independent sediment size and equilibrium bed configurations owing to these assumptions the model is likely to be applicable to only a small subset of vertical stratification sequences observed in shallow marine sandstones as more information on combined flow bed configurations becomes available these assumptions could be relaxed to provide a more refined and complete representation of vertical stratification sequences since the model generates vertical sequences formed from any kind of decelerating flow the bouma sequence for deposits from purely unidirectional turbidity currents and also sequences resulting from decelerating purely oscillatory flows similar in appearance to many proposed generalized tempestite sequences are end member cases in the model the model is also extended slightly to explain the geometry of the uppermost bedding surfaces of storm generated sandstones by consideration of disequilibrium effects

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

the exaerobic zone a new oxygen deficient marine biofacies classical biofacies models1 2 for reconstructing palaeoenvironments of strata deposited in oxygen deficient marine settings define three principal facies aerobic 1 0 ml 1 1 o2 dysaerobic 1 0 to 0 1 ml 1 1 o2 and anaerobic 0 1 ml 1 1 o2 zones these models have postulated a decrease in organism size and degree of calcification as well as a drastic reduction in the relative percentage of fauna possessing calcified skeletons as the dysaerobic anaerobic boundary is approached through use of evidence independent of that provided by body fossils we demonstrate here that in portions of the monterey formation miocene california the bivalve anadara montereyana occurs in situ almost exclusively in strata deposited at the dysaerobic anaerobic boundary the occurrence of fossils of large well calcified benthic macroinvertebrates at this redox boundary contradicts classical biofacies models1 2 and there fore provides the basis for definition of a new oxygen related biofacies the exaerobic zone the exaerobic zone concept when adjusted for differences in basin configuration and palaeoceano graphic conditions provides a potentially useful model for explain ing occurrences of shelly benthic fossils within laminated organic rich strata of other phanerozoic marine sequences

characteristic trace fossil associations in oxygen poor sedimentary environments the sedimentologic record of oxygen poor depositional environments typically includes trace fossils produced by deposit feeding organisms we propose an oxygen controlled trace fossil model in which increasing oxygen concentration of interstitial water in sediment parallels a transition from fodinichnia dominated through pascichnia dominated to domichnia dominated trace fossil associations in certain places such as parts of the late paleozoic oquirrh basin in utah this model provides a reasonable alternative to the more traditional depth controlled model of trace fossil distribution

tropical and extratropical responses of the north atlantic atmospheric circulation to a sustained weakening of the moc abstract the tropospheric response to a forced shutdown of the north atlantic ocean s meridional overturning circulation moc is investigated in a coupled ocean atmosphere gcm the third climate configuration of the met office unified model hadcm3 the strength of the boreal winter north atlantic storm track is significantly increased and penetrates much farther into western europe the changes in the storm track are shown to be consistent with the changes in near surface baroclinicity which can be linked to changes in surface temperature gradients near regions of sea ice formation and in the open ocean changes in the sst of the tropical atlantic are linked to a strengthening of the subtropical jet to the north which combined with the enhanced storm track leads to a pronounced split in the jet structure over europe eof analysis and stationary box indices methods are used to analyze changes to the north atlantic oscillation nao there is no consistent signal of a change in the variability of th

re interpretation of the meikirch pollen record swiss alpine foreland and implications for middle pleistocene chronostratigraphy the meikirch drilling site in the swiss midlands north of bern is re interpreted using a combination of sedimentological logging pollen analyses and luminescence dating the sedimentary sequence comprises about 70 m of lacustrine deposits overlain by about 39 m of coarse glacial outwash interpreted to represent at least two independent ice advances pollen analyses of the apparently complete limnic sequence reveal a basal late glacial period followed by three warm phases that are interrupted by two stadial periods meikirch complex the warm periods were previously correlated with the holsteinian and eemian interglacials according to luminescence dating and with consideration of evidence for middle pleistocene climate patterns at other central european sites a correlation of the meikirch complex with marine isotope stage mis 7 is now proposed if this correlation is correct it implies the presence of three intervals with interglacial character during mis 7 however the late middle pleistocene vegetational features of the meikirch complex show significant differences when compared with the pollen record from the velay region central france possible explanations for this discrepancy are distinct middle pleistocene patterns of atmospheric circulation over central europe and a different distribution of vegetation refugia compared to the eemian interglacial and the holocene copyright 2005 john wiley sons ltd

combined controls of sedimentology and diagenesis on seismic properties in lacustrine and palustrine carbonates upper miocene samos island greece

numerical 230th u dating and a palynological review of the holsteinian hoxnian interglacial abstract earth scientists increasingly consider the holsteinian interglacial and mis 11 as synonyms despite the limited number of numerical dates and ambiguous stratigraphic and palynological correlation with the numerical marine isotope timescale hence we present new tims 230th u dates from two fen peat layers of the holsteinian reference site at bossel in northern germany and re evaluate published numerical data from two sites with hoxnian deposits in england a new method for the calculation of methodically controlled minimum 230th u ages mcma was developed the synopsis of the 230th u dates allows a correlation of both the holsteinian and hoxnian interglacials to mis 9 this correlation is supported by supplementary 230th u dates of fen peat from several pre eemian but non holsteinian sites in germany there is palynological evidence for a reliable correlation between precisely investigated and numerically dated holsteinian deposits in poland germany england sw ireland and france an apparently contradictory palynological correlation from the french central massif is discussed

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

reconstructing palaeoclimatic variables from fossil pollen using boosted regression trees comparison and synthesis with other quantitative reconstruction methods abstract we test and analyse a new calibration method boosted regression trees brts in palaeoclimatic reconstructions based on fossil pollen assemblages we apply brts to multiple holocene and lateglacial pollen sequences from northern europe and compare their performance with two commonly used calibration methods weighted averaging regression wa and the modern analogue technique mat using these calibration methods and fossil pollen data we present synthetic reconstructions of holocene summer temperature winter temperature and water balance changes in northern europe highly consistent trends are found for summer temperature with a distinct holocene thermal maximum at ca 8000 4000 cal a bp with a mean t jja anomaly of ca 0 7 c at 6 ka compared to 0 5 ka we were unable to reconstruct reliably winter temperature or water balance due to the confounding effects of summer temperature and the great between reconstruction variability we find brts to be a promising tool for quantitative reconstructions from palaeoenvironmental proxy data brts show good performance in cross validations compared with wa and mat can model a variety of taxon response types find relevant predictors and incorporate interactions between predictors and show some robustness with non analogue fossil assemblages

crosshole seismic imaging for sulfide orebody delineation near sudbury ontario canada crosshole seismic instrumentation based on a piezoelectric source and hydrophone detectors were used to gather seismograms between boreholes at the mcconnell orebody near sudbury ontario high frequency seismograms were recorded across rock sections 50 to 100 m wide containing a continuous zone of massive sulfide ore first arrival traveltimes obtained from a detailed scan were used to create a p wave velocity tomogram that clearly delineated the ore zone refraction ray tracing on a discrete layer model confirmed the main features of the tomogram the survey demonstrated that it is possible to conduct cost effective high resolution crosshole seismic surveys to delineate ore bodies on a scale useful for planning mining operations

anatomy and origin of a cretaceous phosphorite greensand giant egypt late cretaceous epicontinental phosphorites porcelanites cherts dark coloured shales glauconitic sandstones and bioclastic and fine grained carbonate rocks in egypt are examined in terms of their overall depositional and diagenetic framework and stable isotopic and organic geochemical characteristics two main depositional realms are interpreted and correlated through sequence stratigraphic analysis 1 a shallow hemipelagic environment accompanying initial stages of marine transgression and conducive to the formation of organic carbon rich shales biosiliceous sediments and thick phosphorites and 2 a relatively high energy depositional regime accompanying sea level fall during which deltas advanced glauconites were reworked seaward and prograding oyster banks became periodically exposed to episodes of fresh water diagenesis thereby promoting solution collapse phenomena in associated cherts lenticular to massive phosphorites are viewed as the result of current winnowing and concentration of authigenic grains initially precipitated in associated reducing shales and biosiliceous sediments in eastern egypt the phosphorites form winnowed lag layers some of which may have been redeposited down slope in structural lows in the west these sands were concentrated into giant phosphorite sand waves built by reworking of penecontemporaneously deposited phosphatic muds during marine transgression carbon isotopic results substantiate interpretations from modern deposits for limitation of phosphate mineral precipitation with depth in sediments as a result of lattice poisoning however direct desorption of phosphorus to pore waters from detrital iron oxyhydroxide phases also may have been important in the cretaceous setting the iron reduced in this process being available for incorporation in glauconites the main locus for authigenic glauconite precipitation appears to be where iron fluxes from regions of lateritic weathering were highest and near the boundary between oxygenated and reduced waters this study suggests a model for the common coexistence of glauconites and phosphorites in the geological record although upwelling is often advocated as the origin of nearly all giant phosphorite deposits we suggest that some of these may have been strongly influenced by fluvially derived phosphorus borne on particulates and desorbed from these compounds upon flocculation and or reduction in bottom waters or pore waters

mid cycle condensed shellbeds from mid pleistocene cyclothems new zealand implications for sequence architecture richly fossiliferous and disconformity bounded facies successions termed mid cycle condensed shellbeds mcs occupy a mid cycle position within depositional sequences in the castlecliff section mid pleistocene wanganui basin new zealand these shell rich intervals 0 1 4 5 m thick comprise the upper of two loci of shell accumulation in castlecliff sequences the lower disconformable contacts are sharp and variably burrowed and are interpreted as submarine transgressive surfaces formed by storm or tidal current erosion at the feather edge of contemporary transgressive systems tracts above i e seaward of this erosion surface macrofossil remains mainly bivalves and gastropods accumulated with little reworking on the inner shelf under conditions of reduced terrigenous sediment supply the upper contacts are sharp transitions from shell rich to relatively shell poor lithofacies parautochthonous shell accumulation was quenched by downlapping highstand systems tract shelf siltstones and muddy fine sandstones castlecliff mcs together with the basal shell rich part of overlying highstand systems tracts occupy a stratigraphic position which corresponds to the condensed section that forms at the transgressive highstand systems tract boundary in the sequence model of haq et al 1987 palaeoenvironmental analysis indicates that castlecliff mcs are substantially if not entirely transgressive deposits this study therefore shows that the condensation maximum within a depositional sequence does not necessarily bracket the transgressive systems tract highstand systems tract boundary

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

pollen based palaeoclimate reconstructions over long glacial interglacial timescales methodological tests based on the holocene and mis 5d c deposits at sokli northern finland palaeoclimatic reconstructions over long glacial interglacial timescales present major methodological challenges as calibration methods based on modern climate and vegetation patterns may yield biased reconstructions from non analogue palaeoclimates such as severely continental glacial periods in this work we present pollen based summer temperature reconstructions based on holocene and early weichselian marine isotope stages mis 5d c deposits at sokli northern finland we attempt to improve the robustness of reconstructions of continental palaeoclimates by using two calibration sets with one located in the region surrounding the fossil site and another in a more continental region in northwestern russia we assess the reliability of the reconstructions by estimating the compositional fit between fossil and calibration samples and by comparison with independent plant macrofossil based reconstructions we find the fossil samples to fit the extra regional high continentality calibration set better during the early holocene and mis 5d c especially in mis 5d c however even the high continentality calibration set fits the fossil samples poorly compared to the fit achieved in the mid and late holocene thus our results highlight the problem of finding applicable calibration data for pre holocene periods we finally discuss the relative strengths and vulnerabilities of different calibration methods in reconstruction of non analogue palaeoclimates copyright 2013 john wiley sons ltd

seismic waveform inversion in the frequency domain part 2 fault delineation in sediments using crosshole data a crosshole experiment was carried out in a layered sedimentary environment in which a normal fault is known to cut through the section initial traveltime inversions produced stable but low resolution images from which the fault could be only vaguely inferred to image the fault wavefield inversion was used to produce a velocity model consistent with the detailed phase and amplitude of the data at a number of frequencies our wavefield inversion scheme uses a classical descent type algorithm for decreasing the data misfit by iteratively computing the gradient of this misfit by repeated forward and backward propagations our propagator is a full wave equation frequency domain acoustic finite difference method the use of the frequency space domain yields computational advantages for multisource data and allows an easy incorporation of viscous effects by running wavefield inversion on the field data a quantitative velocity image was produced that yielded a significantly improved image of the fault when compared with the original traveltime inversions because the original field data were noisy and contained a high degree of multiple scattering from the layering of the sediments the transmitted arrivals were selectively windowed to enhance the image the sediments at the site were strongly attenuating we therefore used a viscoacoustic model during the modeling and the inversion that correctly simulated the observed decrease in amplitude with increasing frequency and source receiver offset furthermore since the traveltime inversion indicated a high degree of anisotropy at the site a fixed homogeneous level of anisotropy was used during the inversion tests at varying levels of anisotropy confirmed the improvement in image quality and in data fit when anisotropy was incorporated the final image was verified by examining the distribution of the residuals in the frequency domain by comparing time domain modeled wavefields with the observed data and by direct comparison with borehole logs

climatic evolution during the middle pleistocene warm period of bilshausen germany compared to the holocene abstract middle pleistocene warm periods are particularly useful for comparison with our present warm period one of them marine isotope stage mis 11 has been considered a potential analogue for the holocene whereas older interglacials e g mis 13 are distinctly different however terrestrial middle pleistocene sites other than the holsteinian and quantitative climate reconstructions for this period are very rare in europe a unique terrestrial site in north central europe is known from bilshausen germany the sediments are varved and indicate that this interglacial lasted 25 000 years more than twice as long as the holocene so far the warm period probably correlates to mis 11 or possibly to mis 13 a new palynological investigation with large pollen counts is presented which forms the basis for quantitative temperature reconstructions based on the probabilistic indicator taxa approach the so called pdf method the range of tree species that formed the vegetation during the bilshausen warm period is reminiscent of the holocene but the vegetational as well as the reconstructed climatic development shows distinct differences no pronounced initial successional phase is recorded in the pollen stratigraphy from bilshausen in addition a mesocratic or optimum phase of forest development as in the holocene is unclear in the bilshausen sequence reconstructed temperature values are several c lower than holocene temperatures for most of the bilshausen interglacial only for several millennia in the late phase of the bilshausen interglacial were july temperatures higher than the holocene july temperatures seasonality was much stronger during the bilshausen interglacial and the temperature trends differ between the two interglacials likely reasons for the pronounced differences are on one hand global temperature insolation changes and atmospheric circulation on the other hand more regional factors such as the configuration of the north sea basin may also be responsible for the colder winter temperatures and stronger seasonality during the bilshausen interglacial compared to the holocene reliable absolute dating of the bilshausen interglacial is needed which would allow a more detailed evaluation of the forcing factors that determined the climate during the bilshausen interglacial

high resolution crosswell imaging of a west texas carbonate reservoir part 3 wavefield separation of reflections using crosswell data collected at a depth of about 3000 ft 900 m in west texas carbonates one of the first well to well reflection images of an oil reservoir was produced the p and s brute stack reflection images created after wavefield separation tied the sonic logs and exhibited a vertical resolution that was comparable to well log resolution both brute stacks demonstrated continuity of several reflectors known to be continuous from log control and also imaged an angular unconformity that was not detected in log correlations or in surface seismic profiling the brute stacks particularly the s wave reflection image also exhibited imaging artifacts we found that multichannel wavefield separation filters that attenuated interfering wavemodes were a critical component in producing high resolution reflection images in this study the most important elements for an effective wavefield separation were the time alignment of seismic arrivals prior to filter application and the implementation of wavefield separation filters in multiple domains particularly in common offset domain the effectiveness of the multichannel filtering was enhanced through the use of extremely fine wellbore sampling intervals in this study 2 5 ft 0 76 m vertical sampling intervals for both source and receiver were used whereas most previous crosswell data sets were collected with much coarser sampling intervals resulting in spatial aliasing and limiting the utility of the data for reflection processing the wavefield separation techniques employed in this study used data volumes and associated filtering operations that were several orders of magnitude larger than those encountered in conventional vsp data analysis

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

pilot experiment for the acquisition of marine sediment properties via small scale tomography system a 3 d high resolution crosswell acoustic tomography system was designed and tested in a shallow water environment this system makes use of a damped least squared inversion technique and is used to construct compressional wave velocity images from measured travel time data use of singular value decomposition allowed checks of the linear inversion confirming the validity of the modeled environment it is shown that when the ratio of width to depth of the cross section is about unity or smaller and the domain has not been overparametrized the inverted image model has sufficiently good figures of merit in resolution and variance to visualize small variations in the magnitude compressional velocity field

traveltime inversion for the geometry of aquifer lithologies crosswell traveltime tomography can provide detailed descriptions of the geometry and seismic slowness of lithologic zones in aquifers and reservoirs traditional tomographic inversions that estimate a smooth slowness field to match traveltime data provide limited information about the dominant scale of subsurface heterogeneity we demonstrate an alternative method called the multiple population inversion mpi that co inverts traveltimes between multiple well pairs to identify the spatial distribution of a small number of slowness populations we also compare the mpi with the split inversion method sim that was recently introduced to address the same problem the lithologies and hydraulic parameters for these populations can then be determined from core data and hydraulic testing the mpi iteratively assigns pixels to a small number of slowness populations based on the histogram of slowness residuals by constraining the number of slowness values this method is less susceptible to inversion artifacts such as those related to slight variations in ray coverage and can resolve finer scale sedimentary structures better than methods that smooth the slowness field we demonstrate the mpi in two dimensions with a synthetic aquifer and in three dimensions with the kesterson aquifer in the central valley of california in both cases the constrained inversion algorithm converges to an equal or smaller average traveltime residual than obtained with unconstrained value tomography the mpi accurately images the dominant lithologies of the synthetic aquifer and provides a geologically reasonable image of the kesterson aquifer

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

time lapse crosswell seismic and vsp monitoring of injected co2 in a brine aquifer seismic surveys successfully imaged a small scale co2 injection 1 600 ton conducted in a brine aquifer of the frio formation near houston texas these time lapse borehole seismic surveys crosswell and vertical seismic profile vsp were acquired to monitor the co2 distribution using two boreholes the new injection well and a pre existing well used for monitoring which are 30 m apart at a depth of 1 500 m the crosswell survey provided a high resolution image of the co2 distribution between the wells via tomographic imaging of the p wave velocity decrease up to 500 m s the simultaneously acquired s wave tomography showed little change in s wave velocity as expected for fluid substitution a rock physics model was used to estimate co2 saturations of 10 20 from the p wave velocity change the vsp survey resolved a large 70 change in reflection amplitude for the frio horizon this co2 induced reflection amplitude change allowed estimation of the co2 extent beyond the monitor well and on three azimuths the vsp result is compared with numerical modeling of co2 saturations and is seismically modeled using the velocity change estimated in the crosswell survey

a geostatistical framework for incorporating seismic tomography auxiliary data into hydraulic conductivity estimation abstract a geostatistical approach is presented for the inclusion of seismic tomography data and sonic log data into the estimation of hydraulic conductivity the procedure accounts for the errors in seismic tomography inversion and for the correlation of such errors the proposed methodology consists of two steps 1 the cross variogram inference is carried out using only the data at the wellbore both hydraulic and seismic 2 a co kriging procedure takes the cross well data into account to interpolate between boreholes no postulated a priori relationship is needed in order to illustrate the methodology a synthetic data set is generated on the basis of evidence from published case studies and simplified physical considerations the numerical experiments show that the choice of the excitation frequency is critical a trade off exists between the need for a high resolution survey asking for higher frequencies and the need for a good correlation between hydraulic conductivity and seismic properties asking for frequencies below the squirt frequency of the medium in the simulation using seismic data with the best excitation frequency 1 khz in this case the mean squared error of the hydraulic conductivity estimate is two thirds lower than using hydraulic data alone it is important to note also that only a part of the interwell region is adequately sampled by the tomographic experiment such a region can be readily identified by calculating the energy of the quasi null space through singular value decomposition of the tomographic matrix in planning this type of experiments it is necessary to carefully verify case by case whether the adopted range of high frequencies does not prevent the seismic energy from propagating effectively from sources to receivers

substrate controlled ichnofacies along a marine sequence boundary the intra valanginian discontinuity in central neuquen basin argentina abstract the intra valanginian discontinuity in the neuquen basin argentina marks a dramatic sea level fall within lower cretaceous strata and can be mapped for tens of kilometers both along depositional strike and dip in the proximal region of the lowstand configuration the subaerial segment of the sequence boundary is demarcated by alluvial conglomerates basal mulichinco formation onto deep marine black shales vaca muerta formation in the distal marine realm the time equivalent marine sequence boundary separates black shales and marls beneath from shallow marine carbonate deposits above this paper documents and discusses substrate controlled trace fossils demarcating the marine sequence boundary across more than 30 km in a proximal distal transect in order to shed light onto processes affecting the sea floor during the generation biogenic modification and preservation of this regionally extensive omission surface the downdip expression of the marine sequence boundary is well exposed across a 20 km long strike oriented outcrop everywhere in this region the discontinuity is demarcated by robust thalassinoides with well defined walls and circular cross sections suggesting that the marly substrate was relatively firm during excavation the burrow system is filled with bioclasts of echinoids and bivalves not present in underlying strata up to pebble size intraclasts that were eroded from the underlying succession and authigenic minerals glauconite phosphates this trace fossil suite illustrates the glossifungites ichnofacies the updip expression of the marine sequence boundary in the study area was recorded in a cored well located about 20 km from the outcrops as in the distal region a first generation of passively filled thalassinoides excavated into a firm marly substrate is attributed to the glossifungites ichnofacies however this suite is cross cut at the top by gastrochaenolites and other unidentified borings bored intraclasts also occur above the omission surface this trace fossil suite represents the trypanites ichnofacies the intra valanginian discontinuity records a complex history after the onset of the dramatic sea level fall extensive erosion and exhumation of previous sediments as well as early cementation combined to produce different types of substrates during the generation of the omission surface firmgrounds and hardgrounds colonization of firm substrates probably started firstly in proximal regions when relative sea level was still falling during early transgression firmgrounds were occupied in distal regions and borers colonized the hardgrounds developed in proximal regions thus the surface demarcates a composite surface involving a sequence boundary plus a transgressive surface draped in turn by a mixing of sediments suggesting siliciclastic starvation the generation and preservation of the features associated with the intra valanginian discontinuity are thought to result from the combination of a ramp type pre existing morphology coupled with a high amplitude sea level fall and a relatively deep marine setting prior to the formation of the omission surface

inner shelf to lower shoreface hummocky sandstone bodies with evidence for geostrophic influenced combined flow lower cretaceous west greenland abstract hummocky sandstone bodies were deposited on the margin of an early cretaceous rift basin in an overall progradational inner shelf to lower shoreface unit excellent outcrops of this unit permitted a detailed study of sedimentary structures and paleocurrents in relation to sandstone geometries the sandstone bodies are lensoid and 0 5 4 m thick with lateral extensions from a few meters to more than 30 m laterally they pinch into thin sandstone sheets that continue for at least 130 m along the entire outcrop or swell within a distance of 20 30 m to form another sandstone lens the lower boundaries are sharp with local erosional relief up to 1 m hummocky cross stratification wave ripple cross lamination and low angle cross stratification are closely interbedded within the sandstone aminated mudstone beds 10 60 cm thick separate the sandstone bodies and are generally continuous over the entire length of the outcrop sedimentary structures in the sandstone bodies were produced by high energy wave generated oscillatory currents and unidirectional geostrophic currents vertical stratification successions from individual storm events reflect deposition during both increasing storm current velocity succeeded by waning storm deposits and more typically waning storm facies successions deposition of the unusual vertical successions was probably controlled by an episodically high sediment supply the local presence of the hummocky sandstone bodies on a regional scale was controlled by a paleogeographic setting where the bathymetric contours locally caused geostrophic cu rents to decelerate

applications of boundary preserving seismic tomography for delineating reservoir boundaries and zones of co2 saturation abstractdelineating reservoir units is still a challenge for seismic approaches even high resolution crosswell tomographic approaches that produce smooth velocity models to match traveltime data usually provide limited information about the boundaries of subsurface targets a recent development of seismic traveltime tomography incorporated with a boundary preserving regularization constraint promisingly helps to resolve ambiguities in reservoir boundaries while allowing lateral variations we applied a kind of boundary preserving traveltime tomography to delineate boundaries of the reservoir and co2 saturated zones we chose the minimum gradient support as the regularization to preserve boundaries of the geologic target by penalizing smaller model gradients and smoothing small model variations caused by noise we evaluated several synthetic and real data applications synthetic examples demonstrated that the boundary preserving algorithm produced improved recovery of the profile shape and velocity value