carbon isotope and magnetic polarity evidence for non depositional events within the cambrian ordovician boundary section near dayangcha jilin province china carbon isotope and magnetic polarity stratigraphic results from the cambrian ordovician boundary section at xiaoyangqiao near dayangcha jilin province china in comparison to a contemporaneous section at black mountain australia indicate strata equivalent to major portions of the australian sequence are either absent or are restricted to highly condensed intervals these intervals are correlative with regressive sea level events identified in australia and western north america suggesting regional or eustatic sea level changes strongly influenced deposition of the xiaoyangqiao sequence these results also suggest the xiaoyangqiao section is unfavourable as the site of the cambrian ordovician boundary global stratotype section and point

short climatic oscillations in a western european loess sequence kesselt belgium this new study of the loess section at kesselt is focused mainly on the reconstruction of palaeoenvironments of the last glacial period in the belgian dutch region detailed grain size analyses in combination with the study of the palaeosols and periglacial structures indicate the occurrence of climatic cycles during loess deposition permafrost development coincided with enhanced deposition of relatively coarse loess and alternated with permafrost degradation decreased deposition of finer loess and tundra soil formation a newly designated palaeosol lafelt soil is described in detail particularly in terms of its micromorphological properties it is a luvisol and its chronostratigraphical position is still open to debate but radiocarbon dating places it in the weichselian middle pleniglacial 1998 john wiley sons ltd

the krasnouralsky profile in the middle urals russia a tomographic approach to vintage dss data abstract the middle urals region has been widely studied with geophysical methods over the past decades an integrated program is in progress to summarize this knowledge including modern reprocessing of controlled source seismic data this work is devoted to the krasnouralsky dss profile we applied modern tomography inversion algorithms in 2d and 2 5d on first break traveltime picks from an archive catalogue a number of initial models and various smoothing constraints were used to investigate the influence of starting models on the final model robustness and uncertainty of the recovered models were estimated with hypothesis testing and checkerboard tests the recovered velocity structure shows a thicker crust below the contact of the west uralian zone and the central uralian zone and below the tagil magnitogorsk zone deep high velocity anomalies on both sides of this zone are interpreted as crustal thinning or alteration of the crust by intrusions of mantle material our results suggest that it is worthwhile reinterpreting dss traveltime data with modern inversion techniques

final palaeolithic settlements of the campine region ne belgium in their environmental context optical age constraints abstract the sand sequences exposed at the archaeological sites of arendonk korhaan and lommel maatheide offer a unique means to study the possible relation between human occupation patterns and climatic and environmental changes during the weichselian holocene transition in the campine region ne belgium of particular importance is that at these localities the final palaeolithic and early mesolithic settlement phases are stratigraphically separated optically stimulated luminescence osl dating established a chronology for the evolution of the physical landscape around these sites such a framework is essential when trying to understand settlement dynamics in response to environmental forcing thirty samples in total were dated using quartz sar osl the luminescence ages range from 16 2 1 4 ka to 10 6 0 7 ka they indicate that sand deposition at arendonk and lommel was already going on during the final phase of the late pleniglacial and or the onset of the late glacial at arendonk sediments and soils from the early late glacial until the allerod are missing whereas a single interruption in the aeolian activity during the allerod interstadial is reported for lommel landscape stabilisation during the allerod is also suggested by stratigraphical evidence i e the presence of a bleached horizon both at elevated and low lying flat areas and extensive peat growth in wet depressions the bolling interstadial on the other hand has not been recognised in the lithostratigraphic record this corroborates earlier suggestions that the climatic amelioration during the bolling was not accompanied by a general stabilisation of the land surface in the nw european lowlands the continuation of sand transport and deposition across the late pleniglacial late glacial boundary may explain why human societies did not occupy the campine region until the allerod during this interstadial environmental conditions improved sufficiently to attract final palaeolithic federmessergruppen to settle on higher grounds in the area the climate deteriorated at the onset of the late dryas and as a consequence aeolian activity intensified again at arendonk and lommel with at least 0 5 1 m of sand being deposited in a period of 1 ka this may have caused the federmesser to leave the area at both localities no occupation has been attested for the late dryas period until the early holocene when early mesolithic societies settled in the area this study illustrates how luminescence dating can contribute to an improved understanding of the environmental context around archaeological sites in the campine region

cambrian depositional history of the zanskar valley region of the indian himalaya tectonic implications a well preserved cambrian section in the zanskar valley of northern india has previously been interpreted to record the transition from a passive to an active tectonic margin related to cambrian ordovician orogenesis this interpretation has been used to support the tectonostratigraphic interpretation of other successions across the tethyan himalaya our detailed paleoenvironmental analysis significantly revises the tectonic and depositional history of these cambrian deposits no definitive record of impending cambrian ordovician orogenesis is recorded in these late middle cambrian rocks a critical transition from an 125 m thick stromatolite bearing carbonate deposit the karsha formation into shale and sandstone of the kurgiakh formation was interpreted to represent tectonically induced drowning of a carbonate platform siliciclastic strata of the kurgiakh formation were thought to record deep water flysch deposition in a tectonically active foreland basin next to an arc trench system this interpretation was based on sandstone beds with classic bouma sequences we show that these event beds in the kurgiakh instead contain hummocky cross stratification quasi planar lamination and combined flow ripple stratification all of which reflect deposition in shallow marine storm influenced environments thus although the karsha carbonate platform may have been drowned it did not culminate in deep sea flysch deposition and this in turn eliminates a major line of evidence linking kurgiakh deposition to the onset of cambrian ordovician orogenesis other aspects of cambrian ordovician deposits of northern india also shed doubt on the proposed link between kurgiakh sedimentation and the cambrian ordovician orogenic event first our improved biostratigraphic database suggests that the transition from the karsha carbonate to the kurgiakh formation may have predated the main phase of cambrian ordovician orogenesis as recorded by overlying ordovician molasse by as much as 20 30 my second published data from the ordovician molasse indicate northward paleocurrents which are parallel to those recorded by siliciclastic deposits of the parahio formation below the karsha and thus are at odds with standard models of foreland basin development for the cambrian ordovician event our sedimentological analysis of depositional cycles of the parahio formation indicates that these strata record storm influenced environments from offshore marine to shoreface to fluvial settings this is at odds with previous paleoenvironmental interpretations that ranged from deep sea flysch to intertidal deposits paleocurrent data for marine and fluvial facies of the parahio formation in both zanskar and the spiti valley to the south indicate northeast sediment transport this supports the view that the parahio and overlying carbonate of the karsha formation record the ancient northern passive margin of india during the cambrian and that these strata may be distal equivalents of the younger cambrian deposits of the lesser himalaya

detrital zircon reference for the north china block abstract u pb analyses of 250 single detrital zircons from upper proterozoic to ordovician strata collected from the zhuozi shan in north central china provide a detrital zircon reference for the north china block a major crustal entity in the asian tectonic collage the results which range in age from 1 72 to 2 97 ga shed new light on the age of the crystalline basement in north china much of which is covered by younger sedimentary units in addition this detrital zircon reference can be used to help determine the provenance of clastic sedimentary units and for assessing validity of paleogeographic and regional tectonic models that include the complex history of asian continental amalgamation terrane accretion and subsequent translation that is ongoing today

applying waveform inversion to wide angle seismic surveys abstract multi scale frequency domain acoustic waveform inversion was applied to refraction and wide angle reflection seismic surveys of the upper crust across the plate bounding san andreas fault california and the chesapeake bay impact structure virginia this paper presents and compares the data the preconditioning and different inversion strategies the inversions start at 3 hz and they are stopped at 15 hz due to increasing non linear artifacts the resulting waveform models show a significant improvement in resolution compared to the traveltime starting models but they do not achieve the resolution demonstrated in synthetic studies possible reasons for this limitation are discussed especially the possibility of insufficient bandwidth and the effect of normalizing amplitudes the comparison of results from normalized amplitude and true amplitude waveform inversions indicates that amplitudes do not strongly constrain the velocity structure phase coherency weights are presented that mitigate the impact of noise maps of phase misfits provide a quantitative overview of the data residuals and some insight into the spatial distribution of errors they are helpful for monitoring the progress of the inversion and for determining if and when it must be stopped

crosshole seismic waveform tomography i strategy for real data application summary the frequency domain version of waveform tomography enables the use of distinct frequency components to adequately reconstruct the subsurface velocity field and thereby dramatically reduces the input data quantity required for the inversion process it makes waveform tomography a computationally tractable problem for production uses but its applicability to real seismic data particularly in the petroleum exploration and development scale needs to be examined as real data are often band limited with missing low frequencies a good starting model is necessary for waveform tomography to fill in the gap of low frequencies before the inversion of available frequencies in the inversion stage a group of frequencies should be used simultaneously at each iteration to suppress the effect of data noise in the frequency domain meanwhile a smoothness constraint on the model must be used in the inversion to cope the effect of data noise the effect of non linearity of the problem and the effect of strong sensitivities of short wavelength model variations in this paper we use frequency domain waveform tomography to provide quantitative velocity images of a crosshole target between boreholes 300 m apart due to the complexity of the local geology the velocity variations were extreme between 3000 and 5500 m s 1 making the inversion problem highly non linear nevertheless the waveform tomography results correlate well with borehole logs and provide realistic geological information that can be tracked between the boreholes with confidence

depositional history tectonics and provenance of the cambrian ordovician boundary interval in the western margin of the north china block comment myrow et al 2015 detailed the sedimentology biostratigraphy and chemostratigraphy of the cambrian ordovician succession in the western north china block or sino korean block at wuhai inner mongolia china and recorded an 30 m y unconformity that formed during the upper cambrian series 3 upper middle ordovician they provided a valuable description of the succession accompanied by excellent illustrations of sedimentary facies as well as detailed data on chemostratigraphy thus providing an important basis for further geologic studies in the region in addition they presented a discussion on the origin of the 30 m y unconformity and suggested that the western sino korean block would have been placed near the western himalaya during the early paleozoic where a hiatus of similar magnitude has been reported myrow et al 2006 2016 this result seems to support the theory of mckenzie et al 2011 who first suggested a close paleogeographic affinity between the sino korean block and himalaya based on detrital zircons and trilobites however the paleogeographic interpretation of myrow et al 2015 requires further discussion because of the following reasons 1 incorrect description of the unconformities in other localities of the sino korean block and 2 presence of other potential options on the formative mechanism of this unconformity including tectonic tilting and eustatic sea level change in the following section we describe each topic in detail and discuss the nature and implication of this unconformity

the middle late cambrian reef transition and related geological events a review and new view abstract the reefs of the middle late cambrian cambrian epoch 3 furongian have long been simply considered as microbialites that flourished in the aftermath of the archaeocyath extinction thorough review of the reefs in these periods shows however that the cambrian epoch 3 and the furongian actually yield different types of reefs the cambrian epoch 3 reefs are dominated by thrombolites and dendrolites largely constructed by the calcified microbes epiphyton and renalcis on the other hand the furongian reefs consist mainly of maze like maceriate reefs and columnar stromatolites the maceriate reefs most likely formed by siliceous sponges and calcified microbes including girvanella and tarthinia whereas the columnar stromatolites were mainly constructed by girvanella tarthinia and minor siliceous sponges other microbial reefs e g non columnar stromatolites persisted during the cambrian epoch 3 and the furongian mainly as small patch reefs or reefal crusts lithistid sponge microbial reefs initially formed in the cambrian epoch 3 and occurred throughout the furongian but occupied only a minor portion during these periods several geological events occurred across the boundary between the cambrian epoch 3 and the furongian including positive carbon and sulfur isotope excursions a eustatic sea level drop major faunal turnover of trilobites and diversification of new organisms the coincidence of these events and the transition in reefal fabrics suggest that reef ecosystems were significantly influenced by at least some of these events among the events it is likely that sea level change would have affected reefs although further studies are required in order to test whether and how the other events influenced the reef transition epiphyton and renalcis and thrombolites and dendrolites formed by them declined greatly most likely due to sea level fall and thus decreased in shallow marine habitat at the end of cambrian epoch 3 the cambrian epoch 3 thrombolites and dendrolites were gradually replaced by a sponge microbial association of the maze like maceriate reefs and the columnar stromatolites in the furongian coincident with a sea level rise

detrital zircon provenance of the late triassic songpan ganzi complex sedimentary record of collision of the north and south china blocks the majority of the songpan ganzi triassic flysch sequence is believed to have derived from denudation of the dabie and sulu ultrahigh pressure uhp metamorphic belt in eastern china e g nie et al 1994 1 zhou and graham 1996 2 however intense debate still exists on the sources of

geochronology geochemistry and nd hf isotopes of the xiaokouzi granite from the helanshan complex constraints on the paleoproterozoic evolution of the khondalite belt north china craton abstract the khondalite belt is one of the three paleoproterozoic mobile belts in the north china craton and was formed by a continental collision between the yinshan and ordos blocks at ca 1 95 ga although the metamorphism geochemistry and geochronology of the khondalite belt have been extensively studied the provenance and depositional setting of the khondalite protoliths remain controversial in this study u pb zircon ages and geochemistry of the xiaokouzi granite in the southern helanshan complex part of the khondalite belt are investigated zircon u pb dating indicates that the xiaokouzi granite was formed between 2023 14 ma and 2034 16 ma the granite shows variable sio2 64 33 74 14 wt moderate al2o3 14 75 17 23 wt and a cnk values 1 09 1 66 low cao 0 33 2 35 wt tio2 0 30 0 66 wt tfe2o3 2 58 5 76 wt mgo 0 82 2 32 wt and k2o 2 57 4 96 wt contents these features indicate that the xiaokouzi granite is a peraluminous s type granite the xiaokouzi granite has cr and ni contents of 32 7 84 5 ppm and 10 7 19 3 ppm respectively the granite is enriched in cs k pb and zr and depleted in nb ta p and ti the granite displays variable nd t values 1 7 to 3 5 with a corresponding two stage nd model age of 2 2 2 5 ga in addition the granite has high initial 176hf 177hf ratios 0 281569 0 281789 and positive hf t values 1 1 to 8 1 with a two stage hf model age of 2 2 2 6 ga suggesting a juvenile source the crystallization age of the xiaokouzi granite is synchronous with the peak in the detrital zircon age population from metasedimentary rocks in the khondalite belt in addition hf isotope values from the xiaokouzi granite are consistent with the detrital zircons from metasedimentary rocks together with other paleoproterozoic igneous rocks in the khondalite belt it is inferred that paleoproterozoic magmatic rocks in the khondalite belt may be the potential provenance for khondalite protoliths combined with previous geological data from the khondalite belt we propose that the helanshan khondalite protoliths were most likely deposited in an active continental margin near the ordos block

quantitative imaging of the permo mesozoic complex and its basement by frequency domain waveform tomography of wide aperture seismic data from the polish basin in this study we present the workflow and results of 2d frequency domain waveform tomography applied to the global offset seismic data acquired in central poland along a 50 km long profile during the grundy 2003 experiment the waveform tomography method allows full exploitation of the wide aperture content of these data and produces in a semi automatic way both the detailed p wave velocity model and the structural image i e perturbations in respect to the starting model thirteen frequencies ranging from 4 to 16 hz were inverted sequentially gradually introducing higher wavenumbers and more details into the velocity models although the data were characterised by relatively large shot spacings 1 5 km we obtained clear images both of the mesozoic and permian sedimentary cover velocity patterns indicated facies changes within the jurassic and zechstein strata a high velocity layer ca 5500 m s was found near the base of triassic scythian which made the imaging of a deeper layer difficult nevertheless we were able to delineate the base of the permian i e base of the rotliegend which was not possible to derive from conventional common depth point processing as well as some deeper events attributed to the carboniferous the sub permian events formed a syn form which favoured our previous interpretation of a depression filled with upper carboniferous molasse the validity of the waveform tomography derived model was confirmed by well log data forward ray tracing modelling and synthetic seismograms calculations provided another justification for the key structures present in the waveform tomography model

full waveform inversion of seismic reflection data from the forsmark planned repository for spent nuclear fuel eastern central sweden the swedish nuclear fuel and waste management company skb has been carrying out extensive studies at the planned repository for spent nuclear fuel at the forsmark site in the eastern part of central sweden since 2002 identification of subhorizontal to gently dipping seismic reflections is especially important since these may represent transport routes for radionuclides studies have shown that such reflections can be generated by water filled fracture zones that have a lower velocity than the surrounding bedrock lithological changes that is mafic sills may also be responsible for reflections in some cases at the forsmark site it is difficult to distinguish fracture zones from mafic sills in the standard reflection seismic processed sections however since mafic sills usually have a positive velocity contrast with the background velocity field compared to fractures zones that have a negative one the two possibilities could be differentiated if we could reconstruct the underground velocity field seismic full waveform inversion has the potential to perform this reconstruction allowing us to discriminate between fractures zones and mafic sills in this study we apply a 2 d waveform inversion code on crooked line data sets acquired at the forsmark site this implies we are dealing with a 3 d geometry we handle this problem by applying 3 d to 2 d coordinate projections first we perform a synthetic benchmark test with a similar geometry to that of the projected real data we test both amplitude and phase inversion and phase only inversion on the synthetic data the results show that the phase only inversion has fewer artefacts and is more stable after successful application on the synthetic data we apply the phase only waveform inversion on the real data the resulting velocity fields show more details compared with the starting model based on first arrival traveltime tomography time domain synthetic data sets generated from the final velocity fields show a good match between the early arriving phase of the real data and the synthetic data sets checkerboard tests are also applied on the final models for resolution checks and indicate good resolution down to 200 m in the central parts of the profiles based on a comparison between the kirchhoff pre stack depth migrated sections and the final waveform inversion results we conclude that the reflections investigated most likely are generated at low velocity fracture zones

modelling the evolution of hydrochemical conditions in the fennoscandian shield during holocene time using multidisciplinary information three dimensional large scale models for groundwater flow and solute transport are used for the low temperature fractured crystalline rock sites in sweden that are being considered for the geological disposal of spent nuclear fuel it has been suggested that comparisons between measured and simulated present day hydrochemical data provide a means to constrain the complex influences of past climatic events and to improve the ability to understand the palaeohydrogeological evolution of the physical system studied here the authors demonstrate how the integration of multidisciplinary data and models from one of the sites in sweden forsmark can aid the appraisal of the hydrochemical conditions at 8000 bc which is the selected starting point for the palaeohydrogeological modelling of the hydrochemical conditions in the fennoscandian shield during the holocene last 10 ka since a firm understanding of the evolution of the hydrochemical conditions is important for the long term safety assessment recognition of the initial hydrochemical conditions is essential for the overall build up of confidence in the modelling process

3d seismic traveltime tomography imaging of the shallow subsurface at the c o2 sink project site ketzin germany a 3d reflection seismic survey was performed in 2005 at the ketzin carbon dioxide c o2 pilot geological storage site the c o2 sink project near berlin germany to image the geological structure of the site to depths of about 1 km because of the acquisition geometry frequency limitations of the source and artefacts of the data processing detailed structures shallower than about 150 m were unclear to obtain structural images of the shallow subsurface we applied 3d traveltime tomography to data near the top of the ketzin anticline where faulting is present understanding the shallow subsurface structure is important for long term monitoring aspects of the project after c o2 has been injected into a saline aquifer at about 650 m depth we used a 3d traveltime tomography algorithm based on a combination ofsolving for 3d velocity structure and static corrections in the inversion process to account for artefacts in the velocity structure because of smearing effects from the unconsolidated cover th

brittle tectonic evolution and paleostress field reconstruction in the southwestern part of the fennoscandian shield forsmark sweden 1 six hundred fault slip data have provided robust paleostress fields within an approximately 35 km3 volume of paleoproterozoic 1 9 ga rocks in the southwestern fennoscandian shield forsmark sweden these rocks were affected by penetrative ductile strain from 1 87 to 1 86 ga folding ductile strain along discrete zones around 1 8 ga and semibrittle or brittle deformation around and after 1 8 ga compatible paleostress fields have been identified using site by site and merged data sets from outcrops and oriented drill cores transpressive deformation with a regional nnw sse 1 axis associated with clockwise stress deviation inside a tectonic lens resulted in dextral slip along regionally significant steep wnw ese and nw se deformation zones the semibrittle and most of the brittle structures including specifically the epidote bearing fractures were established during this oldest regime around 1 8 ga latest svecokarelian a younger paleostress field with a ne sw 1 axis which was also transpressive in character is inferred to have been active at 1 7 1 6 ga the best defined paleostress field is transpressive in character with a wnw ese 1 axis that resulted in sinistral reactivation along the wnw ese and nw se zones the main set of laumontite stepped faults developed at this stage at 1 1 0 9 ga sveconorwegian it is impossible to exclude fully the influence of reactivation during even younger phanerozoic tectonic events subordinate extensional paleostress fields were related either to the latest svecokarelian and sveconorwegian transpressive regimes due to 1 and 2 stress permutations or to regional extensional tectonic regimes during the meso or neoproterozoic or later during the permo carboniferous and or mesozoic

waveform tomography imaging of a megasplay fault system in the seismogenic nankai subduction zone abstract we apply frequency domain waveform tomography to form quantitative high resolution p wave velocity images of a megasplay fault system within the central nankai subduction zone offshore of southwest japan using controlled source ocean bottom seismometer obs data originally acquired in 2004 the waveform tomography method exploits recorded seismic waveforms beyond their first arrivals and thus achieves a much higher resolution of the order of a wavelength than that of conventional traveltime tomography methods frequency domain waveform tomography facilitates a multi scale approach to stabilize the inversion in which initial traveltime tomography results are sequentially improved on by first fitting low frequency components of the seismic records starting at 2 25 hz higher frequency components up to 8 5 hz are then introduced progressively our final waveform tomography image allows velocity anomalies as small as 700 m horizontally and 350 m vertically to be discerned and interpreted as confirmed by checkerboard modeling tests the improved explanatory power of the final images is verified by observing that synthetic waveforms calculated from the final results yield much better fit to the observed waveforms than those estimated from the original traveltime tomography image apparent lithological boundaries from waveform tomography agree well with corresponding reflections on seismic migration images providing further confidence in the validity of the results the megasplay fault is evident on the final waveform tomography image as a sharp velocity discontinuity delineating the upper surface of a velocity reduction of nearly 1 km s with respect to the regional 1d velocity trend the megasplay fault can be traced continuously throughout the entire image from a nearly horizontal section at the landward extent moving seaward through to a steeper angle penetrating the old accretionary prisms with several additional splays appearing to branch in the shallow subsurface the location of the low velocity zones imaged by our waveform tomography method coincides with two previously identified low velocity zones the image reveals a low velocity zone that is continuous from deeper to shallower portions of the subsurface suggesting that pore fluids may be transported from the inner wedge to the transition zone and to the surface through fluid conduits associated with the megasplay fault system

thin section analysis as a tool to aid identification of palaeoearthquakes on the slow active geleen fault roer valley graben abstract we analyzed thin sections from two palaeoseismic trenches across the low slip rate geleen fault in the belgian maas river valley to help identifying the most recent large palaeoearthquake on this fault segment in the first trench we sampled silty sediment below and above a prehistoric stone pavement that was supposedly at or near the surface at the time of the event and subsequently thrown down the samples below show a well developed in situ argillic bt soil horizon in parent sediment containing remnants of stratification whereas the sediment above is a structureless colluvium reworked at least partly from bt horizon material below the stone pavement we also found evidence of contorted stratification which is in agreement with macroscopic observations of both the sediment and the stone pavement itself and which is attributed to co seismic soft sediment deformation in the second trench we sampled a sequence of vaguely discernible soil horizons in the hanging wall interpreted as a buried soil profile bt e and possibly a horizons overlain by a featureless deposit thin section analysis supports the colluvial nature of the latter and also provides evidence that both the base of this layer and the top of the poorly developed a horizon below have occupied a shallow position in a soil profile a sample from the same depth in the footwall is composed of very different material instead of colluvium we find patches of bt soil most likely representing the same pedogenic level as the in situ bt horizon at larger depth in the hanging wall but displaced and subsequently degraded furthermore thin sections confirm that vertical structures cutting this bt horizon are sand dykes these dykes could be traced macroscopically upward to the base of the colluvium in both trenches we have thus identified a stratigraphic boundary in the hanging wall close to the surface separating an in situ soil below from colluvium above we interpret this limit and the overlying colluvium as the event horizon and the colluvial wedge respectively of a surface rupturing palaeoearthquake in addition in both cases we found evidence of soft sediment deformation related to liquefaction contemporaneous with the event within the stratigraphic resolution

multiscale seismic imaging of the eastern nankai trough by full waveform inversion 1 classical active seismic methods fail to sharply image the earth s deep crust we present the first crustal scale application of 2 d full waveform inversion based on dense ocean bottom seismic data to investigate the eastern nankai subduction system japan this approach allows to quantify seismic velocities up to an unprecedented degree of resolution results reveal compressive tectonic features within both the subducting oceanic crust and the backstop at depth velocity anomalies along major faults and structural discontinuities bring evidence for the presence of fluids and weakened material and also for a possible coseismic slip partitioning structure index terms 0902 exploration geophysics computational methods seismic 3025 marine geology and geophysics marine seismics 0935 8010 structural geology fractures and faults 8105 tectonophysics continental margins and sedimentary basins 1212 citation dessa j x s operto s kodaira a nakanishi g pascal j virieux and y kaneda 2004 multiscale seismic imaging of the eastern nankai trough by full waveform inversion geophys res lett 31 l18606 doi 10 1029 2004gl020453

cambrian ordovician orogenesis in himalayan equatorial gondwana an early paleozoic tectonic event the kurgiakh orogeny has long been known from the western tethyan himalaya and it is conspicuously recorded by an angular unconformity between cambrian marine shelf deposits and coarse ordovician conglomerate as well as widespread granitic plutons although the lateral extent of this event is poorly known two regions in the central and eastern himalaya the kumaon of india and klippen of bhutan contain conglomerate units that may be correlative with this event in the kumaon the ralam formation which contains a basal polymictic conglomerate unit with detrital zircon grains as young as ca 512 ma is overlain by sandstone containing the arthropod walking trace diplichnites gouldi an ichnospecies known from ordovician and younger strata the late early cambrian trilobite redlichia sp recovered from the underlying martoli group indicates that the conglomerate is post early cambrian and based on stratigraphic analysis also likely records the kurgiakh orogeny in central bhutan the lower paleozoic succession contains conglomerate units with monomictic quartz sandstone clasts and less mature sandstone matrix these units have also been assigned to a variety of ages but rocks that apparently underlie these strata contain the furongian late cambrian zonal trilobite kaolishania granulosa here we show that detrital zircon ages of a conglomerate clast no grains younger than ca 781 ma are distinctly older than those of the matrix which contains a large peak at 490 500 ma thus these conglomerate units are also potential lateral correlatives of the ordovician conglomerate deposits of the western himalaya our paleontological and geochronologic data suggest that the kumaon and bhutan conglomerate units and possible equivalents in tibet correlate with those of the western himalaya this increases their known along strike extent by over 1000 km bringing the total extent to 1200 km thus the kurgiakh orogeny spanned much of the himalayan orogen along the northern gondwanan margin and reflected a widespread tectonic reorganization of the peri gondwanan realm to andean type margins recent work indicates that it also likely extended into the lhasa block and both the north and south china blocks this event was associated with widespread ca 500 ma arc related plutonism recorded in the himalaya and with abundant detrital zircon grains of that age in younger himalaya strata based on current fossil data the duration of the hiatus associated with the cambrian ordovician boundary which separates pre and postdeformational strata ranges from 22 to 36 m y available geochronological data do not provide greater constraint if the event was close in age to the depositional age of the ordovician molasse then the main phase of tectonic uplift erosion and deposition may have been much later than the presumed cambrian ordovician boundary interval age of ca 485 ma

high resolution seismic attenuation imaging from wide aperture onshore data by visco acoustic frequency domain full waveform inversion summary here we assess the potential of the visco acoustic frequency domain full waveform inversion fwi to reconstruct p wave velocity vp and p wave attenuation factor q from surface onshore seismic data first we perform a sensitivity analysis of the fwi based upon a grid search analysis of the misfit function and several synthetic fwi examples using velocity and q models of increasing complexity subsequently we applied both the acoustic and viscoacousticfwitorealsurfacewide apertureonshoreseismicdatafromthepolishbasin wherea strongattenuationoftheseismicdataisobserved thesensitivityanalysisofthevisco acoustic fwi suggests that the fwi can jointly reconstruct the velocity and the attenuation factor if the signatureoftheattenuationissufficientlystronginthedata asyntheticexamplecorresponding to a homogeneous background model with an inclusion shows a reliable reconstruction of vp and q in the inclusion when q is as small as 90 and 50 in the background model and in the inclusion respectively a first application of acoustic fwi to real data shows that a heuristic normalization of the data with offset allows us to compensate for the effect of the attenuation in the data and reconstruct a reliable velocity model alternatively we show that visco acoustic fwi allows us to reconstruct jointly both a reliable velocity model and a q model from the true amplitude data we propose a pragmatical approach based upon seismic modelling and source wavelet estimation to infer the best starting homogeneous q model for visco acoustic fwi we find the source wavelet estimation quite sensitive to the quality of the velocity and attenuation models used for the estimation for example source to source wavelets are significantly more consistent when computed in the final fwi model than in the initial one a good kinematic and amplitude match between the early arriving phases of the real and time domain synthetic seismograms computed in the final fwi model provides an additional evidence of the reliability of the final fwi model we find the recovered velocity and attenuation models consistent with the expected lithology and stratigraphy in the study area we link high attenuation zones with the increased clay content and the presence of the mineralized fluids

brittle tectonothermal evolution in the forsmark area central fennoscandian shield recorded by paragenesis orientation and 40ar 39ar geochronology of fracture minerals in this paper we show how studies of fracture mineral paragenesis their orientation and ar 40 ar 39 geochronology can be applied in order to recognise the brittle tectonothermal evolution in an area samples were selected from nearly 18 km of drill cores from the upper i km of the fennoscandian shield obtained during the site investigation for a repository of spent nuclear fuel in forsmark central sweden four major events of fracturing and or reactivation of fractures associated with fracture mineralisation have been distinguished the first event was characterised by precipitation of epidote quartz and chlorite along preferably sub horizontal and gently dipping fractures or steep wnw ese to nw se fractures precipitation occurred between 1 8 and 1 1 ga possibly during the late stage of the svecokarelian orogeny close to 1 8 1 7 ga the second event is associated with precipitation of hematite stained adularia and albite prehnite laumontite calcite and chlorite preferably along steep ene wsw to nne ssw and nnw sse fractures precipitation occurred around 1107 7 to 1034 3 ma probably due to effects from the sveconorwegian orogeny this event was followed by a period with dissolution of fracture minerals and subsequent precipitation of mainly calcite quartz pyrite and asphaltite during the palaeozoic the formation fluid emanated from an overlying organic rich sedimentary cover precipitation occurred during reactivation of proterozoic fractures but formation of new fractures is also inferred possibly due to far field effects of the caledonian orogeny or elevated hydrostatic pressure due to its foreland basin the latest event is dominated by clay minerals chlorite and calcite along hydraulically conductive fractures these minerals are prominent along sub horizontal and gently dipping fractures but also occur in sets of steeply dipping fractures it is inferred that the hydraulically conductive fractures are proterozoic structures in which mineral precipitation has occurred during a long period however some of the near surface sub horizontal fractures may be quaternary in age c 2009 elsevier b v all rights reserved less

three dimensional p and s wave velocity structure of redoubt volcano alaska the three dimensional p and s wave structure of redoubt volcano alaska and the underlying crust to depths of 7 8 km is determined from 6219 p wave and 4008 s wave first arrival times recorded by a 30 station seismograph network deployed on and around the volcano first arrival times are calculated using a finite difference technique which allows for flexible parameterization of the slowness model and easy inclusion of topography and source receiver geometry the three dimensional p wave velocity structure and hypocenters are determined simultaneously while the three dimensional s wave velocity model is determined using the relocated seismicity and an initial s wave velocity model derived from the p wave velocity model assuming an average vp vs ratio of 1 78 convergence is steady with approximately 73 and 52 reduction in p and s wave arrival time rms respectively after 10 iterations the most prominent feature observed in the three dimensional velocity models derived for both p and s waves is a relative low velocity near vertical pipelike structure approximately 1 km in diameter that extends from 1 to 6 km beneath sea level this feature aligns axially with the bulk of seismicity and is interpreted as a highly fractured and altered zone encompassing a magma conduit the velocity structure beneath the north flank of the volcano between depths of 1 and 6 km is characterized by large lateral velocity variations high velocities within this region are interpreted as remnant dikes and sills and low velocities as regions along which magma migrates no large low velocity body suggestive of a magma chamber is resolved in the upper 7 8 km of the crust

application of waveform tomography to marine seismic reflection data from the queen charlotte basin of western canada to obtain a higher resolution quantitative p wave velocity model 2d waveform tomography was applied to seismic reflection data from the queen charlotte sedimentary basin off the west coast of canada the forward modeling and inversion were implemented in the frequency domain using the visco acoustic wave equation field data preconditioning consisted of f k filtering 2d amplitude scaling shot to shot amplitude balancing and time windowing the field data were inverted between 7 and 13 66 hz with attenuation introduced for frequencies 10 5 hz to improve the final velocity model two different approaches to sampling the frequencies were evaluated the limited maximum offset of the marine data 3770 m and the relatively high starting frequency 7 hz were the main challenges encountered during the inversion an inversion strategy that successively recovered shallow to deep structures was designed to mitigate these issues the inclusion of later arrivals in the waveform tomography resulted in a veloci

the recommended cambrian ordovician global boundary stratotype of the xiaoyangqiao section dayangcha jilin province china this paper provides a brief outline of the current detailed inter disciplinary work on the xiaoyangquiao section trying to expose all the aspects for reference tied to the global single stratigraphic point gssp concept for defining the cambrian ordovician boundary the 45 m critical interval of this section outcrops very well along the steep bank of a stream and is free from folding faulting intrusions and has not been affected by weathering colour alternation of conodonts and acritarchs and crystallinity indices of illite all indicate a maximum thermal grade of 100 c the lithofacies being of great lateral persistence for a hundred kilometres consists mainly of a rhythmical sequence of lime mudstone and shales deposited in a moderately deep outer shelf environment of quiet water well below the normal storm wave base chemical investigation of the rocks demonstrates strong positive correlation between a12o3 content and those of k2o mgo fe2o3 tio2 be cr co ni zn and ba indicating these components are tied to the clay fractions a stable depositional environment is demonstrated by the uniform chemistries through the boundary interval close to the boundary itself p2o5 contents are low indicating continuous sedimentation at fairly substantial rates the major biological events the biostratigraphic framework and the stratigraphic range of conodont graptolite trilobite and acritarch taxa are illustrated briefly with diagrams following the majority views of the calgary plenary session the boundary level is to be chosen at a point marked by the first appearance datum fad of the selected conodont taxon or taxa in the vicinity of the level close to but below the first influx of nematophorous graptolites the following four points marked by the incoming of conodont taxon or taxa are recommended for consideration of the golden spike 1 fad of cordylodus intermedius at 5 28 m below the first influx of nematophorous graptolites 2 fad of hirsutodontus simpler cordylodus drucei albiconus postcostatus at 5 23 m 3 fad of semiacontiodus lavadamensis utahconus utahensis monocostodus sevierensis at 3 85 m 4 fad of cordylodus lindstromi at 2 23 m for the following reasons the fad of h simplex c drucei a postcostatus is favoured 1 the taxa are all distinct and widely dispersed 2 intensive evolutionary change took place in conodonts graptolites trilobites and acritarchs prior to or after this point all the fossil groups occur together providing correlation with many regions throughout the world 3 the point is in a position between the previously widely accepted boundary levels based on graptolites and trilobites 4 the proposed point lies within a thin laterally persistent rhythmical sequence the fad of cordylodus lindstromi is also a favourable point sharing many advantages mentioned above but this point is less satisfactory in being defined by the fad of a single taxon c lindstromi which also has an extremely small population size an isochron age of 500 7 7 4 ma is determined from clay fractions of mudstones 8 5 m below the proposed point by means of the rubidium strontium method the nd signature determined from conodonts trilobites hyolithids and acrotretid brachiopods has a mean value of 6 7 comparable with that of the coeval oceanic water mass occupying southeastern north america and europe and indicating that northeastern china bordered the same ocean the mean tdm model age determined was 1 26 ga at the time of sedimentation compatible with the mean tdm model age of approximately 1 1 ga for the pacific ocean today the relatively low value of the tdm model age indicates a substantial input from young orogenic volcanic island arcs and terranes

trilobite faunal successions across the cambrian ordovician boundary intervals in korea and their correlation with china and australia abstract the cambrian ordovician boundary in korea lies within the choson supergroup exposed in the taebaeksan basin and has been recognized in the taebaek and yongwol groups the taebaek and yongwol groups show slightly different trilobite faunal successions across the putative cambrian ordovician boundary intervals in the taebaek group saukiid dominated missisquoia onychopyge and kainellid dominated faunas occur successively in the basal part of the tongjom formation while the remaining part of the tongjom formation is poorly fossiliferous the succeeding tumugol formation yields fairly diverse trilobite faunal assemblages of late tremadocian age this implies that the cambrian ordovician boundary in the taebaek group should be placed somewhere within the interval yielding the kainellid dominated fauna in the yongwol group an uppermost cambrian fatocephalus fauna is more or less contemporaneous with the saukiid dominated fauna of the taebaek group while three tremadocian trilobite faunas i e yosimuraspis kainella and shumardia zones in ascending order are well represented in the mungok formation the occurrence of jujuyaspis in the yosimuraspis zone provides a firm basis for locating the cambrian ordovician boundary at the base of the mungok formation these cambrian ordovician trilobite faunas of korea are in general well correlated with those of china and australia

multiscale imaging of complex structures from multifold wide aperture seismic data by frequency domain full waveform tomography application to a thrust belt summary an application of full waveform tomography to dense onshore wide aperture seismic data recorded in a complex geological setting thrust belt is presented the waveform modelling and tomography are implemented in the frequency domain the modelling part is solved with a finite difference method applied to the visco acoustic wave equation the inversion is based on a local gradient method only the p wave velocity is involved in the inversion the inversion is applied iteratively to discrete frequency components by proceeding from low to high frequencies this defines a multiscale imaging in the sense that high wavenumbers are progressively incorporated in images the linearized waveform tomography requires an accurate starting velocity model that has been developed by first arrival traveltime tomography after specific pre processing of the data 16 frequency components ranging between 5 4 and 20 hz were inverted ten iterations were computed per frequency component leading to 160 tomographic models the waveform tomography has successfully imaged southwest dipping structures previously identified from other geophysical data as being associated with high resistivity bodies the relevance of the tomographic images is locally demonstrated by comparison of a velocity depth function extracted from the waveform tomography models with a coincident vertical seismic profiling vsp log available on the profile moreover comparison between observed and synthetic seismograms computed in the starting traveltime and waveform tomography models demonstrates unambiguously that the waveform tomography successfully predicts for wide angle reflections from southwest dipping geological structures this study demonstrates that the combination of first arrival traveltime and frequency domain full waveform tomographies applied to dense wide aperture seismic data is a promising approach to quantitative imaging of complex geological structures indeed wide aperture acquisition geometries offer the opportunity to develop an accurate background velocity model for the subsequent waveform tomography this is critical because the building of the macromodel remains an open question when only near vertical reflection data are considered

structural anatomy of the early paleozoic laohushan ophiolite and subduction complex implications for accretionary tectonics of the proto tethyan north qilian orogenic belt northeastern tibet

weathering of glauconite in soils of temperate climate as exemplified by a luvisol profile from gora pulawska poland abstract the aim of the research reported herein was to study the weathering of glauconite taking place in a luvisol profile developed on quartz glauconitic sand in gora pulawska eastern poland using x ray diffractometry fourier transform infrared spectroscopy mossbauer spectroscopy sem eds and an optical microscope the bulk soil material contains quartz glauconite glauconite smectite mixed layered minerals rich in smectite layers and traces of feldspars when compared with the parent material the cg horizon the bt1 and bt2 horizons are enriched in clay minerals while the ap aeg and e horizons are depleted in clays the observed mineral distribution is most likely controlled by the weathering of clay minerals in the uppermost part of the profile and translocation of clay fractions down the profile lessivage however contamination with glaciofluvial and or aeolian material has to be taken into consideration according to the microscopic observations of the thin sections clay is present in the bcg and cg horizons in the form of clay coatings and clay infilings this indicates that initially the parent sand did not contain clay fraction the fraction was formed most likely in the upper part of the soil profile and was deposited in the lower horizons by percolating atmospheric water green pellets separated from all the soil horizons are composed of glauconite showing more or less uniform chemical composition while clay fractions from all the horizons contain glauconite and glauconite smectite fine clay fractions separated from ap and aeg horizons are enriched in glauconite smectite relative to the fractions separated from the lower horizons the presence of glauconite and glauconite smectite minerals in the clay fractions studied indicates that glauconite weathering in the soil studied involves formation of glauconite clay by the pellet disintegration and glauconite smectitization ferrous iron accounts only for

development of a clay rich interval above a limestone substrate in the condroz region of southern belgium a profile comprising a limestone substrate overlain by a clay rich interval which represents a common sequence was studied with the objective of determining the relationship between substrate and cover the profile was characterized by various types of mineralogical and chemical analyses and by a micromorphological study the mineralogical and chemical data demonstrate that the cover is unrelated to the parent rock including all horizons below the loess derived ap horizon thin section observations show that the basal c3 horizon is largely composed of illuvial clay deposited around claystone fragments resulting in a fabric that together with profile position relates the interval to so called beta horizons in higher parts up to a level recognized as a lithological discontinuity based on mineralogical composition the profile largely consists of fragments of clay coatings and disintegrated claystone fragments with an overall upward increase in degree of pedoturbation the source of the clay is assumed to be cenozoic deposits that are known to occur in the region the main conclusion of this study is that clay intervals overlying limestone can have a complex mode of development to be studied by a combination of methods and with implications for the valorization of existing soil maps

reflection seismic investigations in the dannemora area central sweden insights into the geometry of polyphase deformation zones and magnetite skarn deposits the bergslagen region is one of the most ore prospective districts in sweden presented here are results from two nearly 25 km long reflection seismic profiles crossing this region in the dannemora

an extensive erosion surface of a strongly deformed limestone bed in the gushan and chaomidian formations late middle cambrian to furongian shandong province china sequence stratigraphic implications abstract in order to understand sequence development and sea level fluctuations during the late middle cambrian to early furongian on the north china epeiric platform the present study focuses on a unique subtle erosion surface of an extensive approx 100 km strongly deformed limestone bed in the uppermost part of the gushan formation shandong province china the gushan formation and the overlying chaomidian formation consist mainly of shales and a variety of carbonates that were deposited in subtidal environments e g deep subtidal shallow subtidal shoreface shoal subtidal microbial flat and restricted platform interior three third order depositional sequences s1 3 are identified each of which comprises a thin transgressive systems tract tst and a relatively thick highstand systems tract hst each sequence is bounded by a drowning unconformity sb1 a subaerial unconformity sb2 or a surface of submarine erosion sb3 the upper sequence boundary sb2 of sequence 1 s1 is represented by a subtle erosion surface of an extensive deformed limestone bed with a wide variety of soft sediment deformation structures e g lime mudstone breccias chaotic wacke packstone laminae and fragments homogenized oolites and clastic dykes and is overlain by small sporadic microbial buildups and an extensive bioclastic grainstone bed the deformed limestone was formed during early diagenesis by differential deformation processes brecciation liquefaction fluidization and injection which were most likely induced by pore water overpressure during the period of rapid sea level fall despite the lack of subaerial exposure features e g paleokarst paleosol etc the characteristics of the erosion surface cutting well lithified sediment below the missing of a significant geological record the prochuangia biozone and the worldwide correlatable positive carbon isotope excursion collectively indicate that the erosion surface developed under conditions of subaerial exposure after contemporaneous marine cementation of the deformed sediment the missing of the prochuangia biozone is most likely due to non deposition at a subaerial hiatal surface the erosion surface was submerged as a result of subsequent rise in sea level where sporadic microbial buildups formed under suitable conditions freshly deposited winnowed shell dominated transgressive lag deposits containing chuangia trilobite fragments brachiopod shells and abundant glauconite grains formed with continued rise in sea level which became in turn overlain by shale dominated facies the unique combination of the subtle erosion surface sensu stricto a subaerial unconformity and the underlying deformed limestone bed provides an important criterion for recognizing the subtle changes in relative sea level on shallow epeiric platforms

paleo pedological record of the rocourt pedosequence at veldwezelt hezerwater belgian pleistocene loess belt part 2 soil formation abstract as the environment influences soil formation quaternary loess paleosols provide an important yet complex source on former climate and vegetation conditions this study revises the paleopedological record of the rocourt complex the pedostratigraphic marker for the eemian and early weichselian in the belgian loess belt depth functions were established from an exceptionally well preserved in situ sequence based on soil micromorphological features total element contents iron fractions and carbon content a reconstruction was made of the polygenetic formation of the rocourt soil results indicate that only by combining multiple soil features consistent information could be obtained furthermore this study shows that cryogenic processes transport of colloids iron dynamics redox conditions organic matter formation and biological activity were major soil forming processes the hypothesis of six major stages of soil formation under varying climatic conditions was most supported by the data during the warm to temperate oceanic climate of the eemian a strongly weathered argic horizon was formed this horizon was later disrupted by reticulate ice segregation and stagnogley during the severe and prolonged cold conditions of the first cold stadial following the eemian weak soil formation during the relatively short continental st germain i interstadial subsequently formed cambic soil properties and a humiferous horizon in a mixture of local and new sediments these soils were disrupted by fragipan formation with its associated cryogenic structure banded eluviation and redoxfront during the succeeding stadial with periglacial conditions during the st germain ii another a horizon formed in new calcareous material during more stable climatic conditions allowing organic matter build up eluviation of smectite and formation of pedogenetic iron during the evolution from this warmer climate with forest or forested steppe to eventually periglacial open tundra an accretionary humiferous soil concluded the last episode of soil formation before the onset of pleniglacial weichselian conditions

waveform tomography at a groundwater contamination site vsp surface data set application of 2d frequency domain waveform tomography to a data set from a high resolution vertical seismic profiling vsp experiment at a groundwater contamination site in hill air force base hafb utah reveals a surprisingly complicated shallow substructure with a resolution of approximately 1 5 m variance in the waveform misfit function is reduced 69 4 by using an initial velocity model from first arrival traveltime tomography the waveform tomography model suggests 1 a low velocity layer at 1 to 4 m depth 2 a high vertical velocity gradient of 80 m s m on average and 3 severe lateral variations velocity contrasts as large as about 200 m s occur in a distance as short as 1 5 m the model is well correlated with lithologic logs and is interpreted geologically a q value of 20 is estimated for the target area the extreme lateral and vertical variations of the subsurface compromise many standard seismic processing methods

sequence sequence stratigraphy sea level changes and depositional systems in the cambro ordovician of the north china carbonate platform abstract the cambro ordovician strata in north china were deposited over a very extensive craton extending some 1500 km east west and 1000 km north south the dominantly shallow water carbonate succession reaches up to 2000 m in thickness and two megasequences transgressive regressive cycles can be distinguished lower cambrian through lower ordovician strata and middle through upper ordovician strata separated by a major palaeokarst the first megasequence consists of nine sequences which are generally 50 150 m in thickness the lower cambrian sediments consist of phosphorites and phosphatic sandstones deposited during the flooding of the craton carbonates mudrocks and evaporites were deposited in the early cambrian under an arid climate laying the foundation for the subsequent long period of shallow water carbonate deposition which lasted some 70 m y the middle and lower upper cambrian sequences consist predominantly of mudrocks and storm deposits tempestites in the lower part and oolitic grainstones and tidal flat lime mudstones in the upper part these represent outer mid and mid inner ramp depositional systems respectively of the transgressive and highstand systems tracts these sequences have strong similarities with the grand cycles in the cambro ordovician successions of north america in the upper cambrian there is a distinctive unit of glauconitic purple red mudstone several metres thick which is interpreted as the deposits of the maximum flooding of the first megasequence in the upper cambrian there was a phase of tilting of the north china carbonate platform to the north and storm deposits especially intraclastic conglomerates and hummocky cross stratified grainstones packstones were very common at this time also common in upper middle and lower upper cambrian strata are stromatolitic thrombolitic bioherms several metres in diameter the upper upper cambrian through lower ordovician strata are dominantly fine grained limestones and dolomites deposited in shallow subtidal and inter to supra tidal environments on a low energy epeiric sea platform this part of the succession is the regressive part of the first megasequence so that overall the platform shows an evolution from platform initiation to platform foundation to a ramp depositional system and then an extensive epeiric platform on a small scale the succession is composed of metre scale shallowing upward cycles parasequences arranged into cycle sets of 10 30 m thick the middle upper ordovician megasequence consists mostly of shallow water carbonates with several thick evaporite units minor palaeokarsts and palaeosoils separate the sequences which are composed of metre scale cycles regional uplift affected the north china platform in the ordovician and sedimentation did not resume until the carboniferous there is a good correlation of the two transgressive regressive megasequences described here with the global 2nd order relative sea level curve for the cambro ordovician

sequence stratigraphy of the taebaek group cambrian ordovician mideast korea abstract this study focuses on the sequence stratigraphic implications of the taebaek group cambrian ordovician a mixed carbonate siliciclastic sequence ca 1200 m thick in the mideastern part of the korean peninsula the group contains 11 lithologic units formations that can be partitioned into four packages supersequences i iv each package comprises alternation of siliciclastic and carbonate successions corresponding to the second order sequence supersequence formed in a period of 10 100 m y supersequence i jangsan myeonsan myobong and daegi fms represents the initial inundation and subsequent drowning during the late early to middle middle cambrian it experienced the drowning between the middle and late middle cambrian forming type 3 sequence boundary supersequence ii sesong and hwajeol fms was formed by prolonged marine flooding during the late middle and late cambrian it was terminated by a large supply of siliciclastics due to the rejuvenation of the drainage basin and the subsequent shallowing at the cambrian ordovician boundary type 2 sequence boundary supersequence iii dongjeom dumugol and makgol fms comprises the lowstand coarse grained siliciclastics transgressive shale by marine flooding and shallow platform carbonates by highstand progradation in the early ordovician following the large scale eustatic fall of sea level in the earliest middle ordovician supersequence iv jigunsan and duwibong fms formed on the subaerial exposure surface type 1 sequence boundary by resumed marine flooding in the middle ordovician this study provides basis for basin scale correlation with the coeval sequences in northeastern china

the late cambrian spice δ13c event and the sauk ii sauk iii regression new evidence from laurentian basins in utah iowa and newfoundland carbon isotope data from upper cambrian sections in three laurentian basins in northern utah central iowa and western newfoundland record a large positive d 13 c excursion spice event of up to 1 5 peak d 13 c ratios are well dated by trilobite collections to the middle of the steptoean stage dunderbergia zone and occur during maximum regression associated with formation of the sauk ii sauk iii subsequence boundary on the north american craton max imum regression was marked by an influx of quartz sand into carbon ate platform settings in all three widely separated basins in northern utah this quartz sand formed a thick sequence known as the worm creek quartzite which marks a conspicuous interruption of carbonate deposition during the middle to late cambrian in the region in west ern newfoundland the thickness of the quartz sand unit is much re duced but still marks a brief shutdown of the carbonate factory that is unique to the cambrian shelf succession of the area in the central iowa area of the cratonic interior an upward shallowing carbonate succession culminates in cross stratified trilobite grainstones at the peak of the spice in dunderbergia zone time and the lowest point on the relative sea level curve is associated with the occurrence of coarse quartz sand derived from the encroaching shoreface although it is difficult to determine precisely the departure from baseline d 13 c that marks the beginning of the spice excursion in the stratigraphic successions analyzed our results are consistent with a rise and subsequent fall in d 13 c tracking a major regressive transgressive event recorded across northern laurentia the correlation of a major d 13 c excursion with regression is similar to that described for the late ordovician for which the pattern has been attributed to either in creased carbonate relative to terrigenous weathering rates as ice sheets covered up organic matter containing silicates at high latitudes or high productivity and organic carbon burial driven by oceanic overturn the lack of known steptoean age ice sheets that could have affected the ratio of carbonate to silicate weathering rates suggests that organic carbon burial was the likely cause of the spice event we suggest that increased weathering and erosion rates during relative sea level fall sauk ii iii increased the burial fraction of organic carbon in an expanded region of fine grained siliciclastic deposits in shelf and upper slope environments during the steptoean

finite difference elastic wave propagation in 2d heterogeneous transversely isotropic media1 the velocity stress formulation for propagation of elastic seismic waves through 2d heterogeneous transversely isotropic media of arbitrary orientation is presented the equations are recast into a finite difference scheme and solved numerically using fourth order spatial operators and a second order temporal operator on a staggered grid absorbing free surface and symmetry boundary conditions have been implemented test cases compare well with other published solutions synthetic seismograms are calculated over two idealized models i vertical fractures in granite with a dolerite sill reflector and ii a dipping anisotropic shale comparisons with the isotropic counterparts show significant differences which may have to be accounted for in seismic processing in the future

inverse theory applied to multi source cross hole tomography part 1 acoustic wave equation method1 frequency domain methods are well suited to the imaging of wide aperture cross hole data however although the combination of the frequency domain with the wavenumber domain has facilitated the development of rapid algorithms such as diffraction tomography this has also required linearization with respect to homogeneous reference media this restriction and association restrictions on source receiver geometries are overcome by applying inverse techniques that operate in the frequency space domain in order to incorporate the rigorous modelling technique of finite differences into the inverse procedure a nonlinear approach is used to reduce computational costs the method of finite differences is applied directly to the frequency domain wave equation the use of high speed high capacity vector computers allow the resultant finite difference equations to be factored in place in this way wavefields can be computed for additional source positions at minimal extra cost allowing inversions to be generated using data from a very large number of source positions synthetic studies show that where weak scatter approximations are valid diffraction tomography performs slightly better than a single iteration of non linear inversion however if the background velocities increase systematically with depth diffraction tomography is ineffective whereas non linear inversion yields useful images from one frequency component of the data after a single iteration further synthetic studies indicate the efficacy of the method in the time lapse monitoring of injection fluids in tertiary hydrocarbon recovery projects

archean blocks and their boundaries in the north china craton lithological geochemical structural and p t path constraints and tectonic evolution an examination of lithological geochemical geochronological structural and metamorphic p t path data suggests that the basement of the north china craton can be divided into eastern and western blocks separated by major crustal boundaries that roughly correspond with the limits of a 300 km wide zone called the trans north china orogen the eastern block consists predominantly of late archean domiform tonalitic trondhjemitic granodioritic ttg batholiths surrounded by anastomosing networks and linear belts of open to tight synforms of minor volcanic and sedimentary rocks metamorphosed from greenschist to granulite facies at 2 5 ga with anticlockwise p t paths some early to middle archean rocks are locally present in the eastern block but their tectonic history is unclear due to reworking by the 2 5 ga tectonothermal event the western block has a late archean assemblage structural style and metamorphic history similar to that of the eastern block but it differs in the absence of early to middle archean assemblages and in being overlain by and interleaved with paleoproterozoic khondalites which were affected by a 1 8 ga metamorphic event involving clockwise p t paths a mantle plume model is proposed for the formation and evolution of late archean basement rocks in the eastern and western blocks based on a combination of extensive exposure of ttg gneisses affinities of mafic rocks to continental tholeiitic basalts presence of voluminous komatiitic rocks dominant diaprism related domiform structures anticlockwise p t paths and a short time span from the primary emplacement of ttg and ultramafic to mafic rocks until the onset of regional metamorphism between the two blocks is the trans north china orogen which is bounded by two major fault systems and is composed of late archean to paleoproterozoic ttg gneisses and granitoids interleaved with abundant sedimentary and volcanic rocks that are geochemically interpreted as having developed in magmatic arc and intra arc basin environments these rocks underwent multiple phases of compressional deformation and peak high pressure metamorphism followed by rapid exhumation during the late paleoproterozoic at 1 8 ga as a result of collision between the eastern and western blocks resulting in the amalgamation of the north china craton

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

correlation between fragipans and permafrost with special reference to silty weichselian deposits in belgium and northern france abstract a comparison is made between the properties of permafrost and those of fragipans the permafrost characteristics are summarized from published data on active permafrost and from personal observations on fossil permafrost the study of the fragipans mainly concerns the silty sediments of weichselian age which occur in belgium and northern france the distribution and the physical macromorphological and micromorphological properties of fragipans can all satisfactorely be explained by the growth of segregated ice during permafrost aggradation particularly striking is the relationship of both permafrost and fragipans to drainage conditions the quantity of segregated ice is highest in moist or poorly drained soil and it is at such places that the best developed fragipans are observed certain arguments that can be stated against the hypothesis of fragipan genesis by permafrost are discussed 1 the development of a platy structure by freeze thaw or by wet dry cycles 2 the discontinuous distribution of the fragipan 3 the development of the fragipan by pedogenetic weathering and migration processes it is concluded that only the permafrost hypothesis can explain the complete set of properties of the fragipan

waveform tomography at a groundwater contamination site surface reflection data wehaveappliedacoustic waveformtomographyto452d seismic profiles to image the 3d geometry of a buried paleochannel at a groundwater contamination site at hill air force base in utah the paleochannel which is incised into an alluvium covered clay aquitard acts as a trap for dense nonaqueous phase liquids dnapls that contaminate the shallowest groundwater system in the study area the 2d profiles were extracted from a 3d surface reflection data set first arrival traveltime tomography provided initial velocity models for the waveform tomography we inverted for six frequency components in the band 30 90 hz of the direct and refracted waves to produce 45 2d velocity models the flanks and bottom of a channel with a maximum depth of about 15 m were well modeled in most of the 45 parallel 2d slices whichallowedustoconstructa3dimageofthechannel by combining and interpolating between the 45 image slices the 3d model of the channel will be useful for siting extraction wells within the site remediation program the alluvium that fills the channel showed marked vertical and lateral velocity heterogeneity traveltime tomography and waveform tomography can be complementary approaches used together they can provide high resolution images of complicatedshallowstructures

investigating the use of 3 d full waveform inversion to characterize the host rock at a geological disposal site the u k government has a policy to dispose of higher activity radioactive waste in a geological disposal facility gdf which will have multiple protective barriers to keep the waste isolated and to ensure no harmful quantities of radioactivity are able to reach the surface currently no specific gdf site in the united kingdom has been chosen but once it has the site is likely to be investigated using seismic methods in this study we explore whether 3 d full waveform inversion fwi of seismic data can be used to map changes in physical properties caused by the construction of the site specifically tunnel induced fracturing we have built a synthetic model for a gdf located in granite at 1000 m depth below the surface since granite is one of the candidate host rocks due to its high strength and low permeability and the gdf could be located at such a depth we use an effective medium model to predict changes in p wave velocity associated with tunnel induced fracturing within the spatial limits of an excavated disturbed zone edz modelled here as an increase in fracture density around the tunnel we then generate synthetic seismic data using a number of different experimental geometries to investigate how they affect the performance of fwi in recovering subsurface p wave velocity structure we find that the location and velocity of the edz are recovered well especially when data recorded on tunnel receivers are included in the inversion our findings show that 3 d fwi could be a useful tool for characterizing the subsurface and changes in fracture properties caused during construction and make a suite of suggestions on how to proceed once a potential gdf site has been identified and the geological setting is known

slowing extrusion tectonics lowered estimate of post early miocene slip rate for the altyn tagh fault abstract determination of long term slip rate for the altyn tagh fault is essential for testing whether asian tectonics is dominated by lateral extrusion or distributed crustal shortening previous slip history studies focused on either quaternary slip rate measurements or pre early miocene total offset estimates and do not allow a clear distinction between rates based on the two the magmatic and metamorphic history revealed by shrimp zircon dating of clasts from miocene conglomerate in the xorkol basin north of the altyn tagh fault strikingly matches that of basement in the southern qilian shan and northern qaidam regions south of the fault this match requires that the post early miocene long term slip rate along the altyn tagh fault cannot exceed 10 mm year supporting the hypothesis of distributed crustal thickening for post early miocene times this low long term slip rate and recently documented large pre early miocene cumulative offset across the fault support a two stage evolution wherein asian tectonics was dominated by lateral extrusion before the end of early miocene and since then has been dominated by distributed crustal thickening and rapid plateau uplift

sem and light microscopic observations of minerals in bog ores of the belgian campine abstract stoops g 1983 sem and light microscopic observations of minerals in bog ores of the belgian campine geoderma 30 179 186 soft bog ore deposits are frequently present in alluvial soils of the nete valley province of antwerp belgium a profile was studied consisting of four layers of which the upper three were analyzed with the light microscope and sem scanning electron microscope the top layer consisted mainly of clay and fragmented diatom shells isotropic fe oxihydrates and radiating goethite needles were present in the underlying limonitic layer siderite and vivianite were found in the third layer the former often present in the wall of root channels whereas the latter was frequently found within the channels vivianite was also found associated with decaying roots or alone inside root channels pyrite framboids were also found in the lower part of the profile the presence close to each other of different minerals such as goethite pyrite siderite and vivianite cannot be explained by macroenvironmental mineral equilibria alone it requires the existence of different microenvironments which can vary in time and place the study of such microenvironments however requires additional in situ microchemical submicroscopic techniques

crosshole seismic waveform tomography ii resolution analysis summary in an accompanying paper we used waveform tomography to obtain a velocity model between two boreholes from a real crosshole seismic experiment as for all inversions of geophysical data it is important to make an assessment of the final model to determine which parts of the model are well resolved and can confidently be used for geological interpretation in this paper we use checkerboard tests to provide a quantitative estimate of the performance of the inversion and the reliability of the final velocity model we use the output from the checkerboard tests to determine resolvability across the velocity model such tests can act as good guides for designing appropriate inversion strategies here we discovered that by including both reference model and smoothing constraints in initial inversions and then relaxing the smoothing constraint for later inversions an optimum velocity image was obtained additionally we noticed that the performance of the inversion was dependent on a relationship between velocity perturbation and checkerboard grid size larger velocity perturbations were betterresolved when the grid size was also increased our results suggest that model assessment is an essential step prior to interpreting features in waveform tomographic images

detrital zircon u pb ages of the jangsan formation in the northeastern okcheon belt korea and its implications for material source provenance and tectonic setting abstract the jangsan formation distributed in the taebaeksan basin central eastern korea is unfossiliferous and is composed of quartz arenite this formation is conventionally believed to be the lowermost stratigraphic unit of the lower paleozoic sequence deposited on the yeongnam massif in south korea corresponding to early cambrian in age u pb dating of detrital zircon grains using a laser ablation inductively coupled mass spectrometer yields ages ranging from archean to middle proterozoic 1738 67 ma to 3058 53 ma detrital zircons show no ages younger than 1 8 ga suggesting that the jangsan formation was deposited at some time after this age but much prior to ca 520 ma the depositional age of the immediately overlying myobong formation this interpretation is supported by the recent report on the presence of the unconformity between the jangsan and the myobong formations kim and lee 2006 zircon ages from jangsan sandstones define two major groups archean age grains with a maximum frequency at about 2 5 ga and paleoproterozoic age grains with maximum frequencies at about 2 1 and 1 8 ga the observed zircon age distribution in the jangsan sandstones may represent that of the yeongnam massif on which the jangsan formation was deposited such an age distribution of the yeongnam massif matches well with that the north china block suggestive of the yeongnam massif being a part of the sino korean craton during the precambrian

late paleozoic final closure of the paleo asian ocean in the eastern part of the xing meng orogenic belt constrains from carboniferous permian meta sedimentary strata and meta igneous rocks abstract zircon u pb dating and whole rock geochemical data for carboniferous permian meta sedimentary sequences igneous rocks and precambrian amphibolite in the eastern xing meng orogenic belt xmob were used to constrain the final stage evolution and the position of closure of the paleo asian ocean pao detrital zircons from late paleozoic strata range in age from archean to late paleozoic with major age groups at 1 0 0 7 ga and 0 5 0 25 ga in the northern part and at 2 7 2 5 ga 2 1 1 8 ga and 0 5 0 25 ga in the southern part of the xmob striking changes in zircon age distribution patterns indicate inputs to these strata were separated by the paleo asian ocean pao in the late paleozoic the pao closed along the solonker linxi suture the late paleozoic formation ages 346 ma 303 ma and 269 ma of the igneous rocks with arc like geochemical features south to the pao together with previously published data on the regional igneous rocks and ophiolites indicate double side subduction of the pao in the late paleozoic

full waveform tomography for lithospheric imaging results from a blind test in a realistic crustal model summary a comprehensive validation of 2 d frequency domain acoustic wave equation tomography was undertaken in a blind test using third party realistic elastic wave equation data the synthetic 2 d wide angle seismic data were provided prior to a recent workshop on the methods of controlled source seismology the true model was not revealed to the authors until after the presentation of our waveform tomography results the original model was specified on a detailed grid with variable p wave velocity s wave velocity density and viscoelastic q factor structure designed to simulate a section of continental crust 250 km long and 40 km deep synthetic vertical and horizontal component data were available for 51 shot locations spaced every 5 km recorded at 2779 receivers spaced every 90 m evenly spread along the surface of the model the data contained energy from 0 2 to 15 hz waveform tomography a combination of traveltime tomography and 2 d waveform inversion of the early arrivals of the seismic waveforms was used to recover crustal p velocity structure from the vertical component data using data from 51 sources 1390 receivers and frequencies between 0 8 and 7 0 hz the waveform tomography result contained apparent structure at wavelength scale resolution that was not evident on the traveltime tomography result the predicted acoustic waveforms in the final result matched the original elastic data to a high degree of accuracy during the workshop the exact model was revealed over much of the model the waveform tomography results provided a good correspondence with the true model from large to intermediate wavelength scales with a resolution limit on the order of 1 km a significant near surface low velocity zone invisible to traveltime methods was correctly recovered the results also provided a high resolution image of the complex structure of the entire crust and the depth and nature of the crust mantle transition some inaccuracies were observed near the edges of the images due to the limited ray coverage inherent to the footprint of the survey geometry several aspects of the waveform tomography strategy were critical to the success of the acoustic method with realistic synthetic viscoelastic data i the accuracy of the starting model from traveltime tomography ii implementation in the frequency domain iii the use of complex valued frequencies to effect time damping of the data residuals iv the selection of a suitable subset of data and data frequencies v progressive inversion of low to high frequency components of the data vi initial pre inversion matching of the amplitudes between observed and modelled data and vii sufficient preconditioning of both the data and the update images combined these strategies were effectively equivalent to a multiscale approach that mitigated the non linearity of the seismic inverse problem during the inversion we carried out repeated forward modelling to ensure our modelled waveforms matched the observed data as closely as possible in both frequency and time domains the synthetic data set used in this paper provides a benchmark for future testing of modelling inversion and imaging algorithms for wide angle lithospheric imaging

detrital zircon geochronology of the northeastern tibetan plateau u pb geochronologic analyses have been conducted on 413 detrital zircon grains collected from 16 samples in the altun shan nan shan and qilian shan the samples come primarily from quartz arenites and metaturbidites of middle to late proterozoic age and from feldspathic and volcanic clast rich sandstones of early paleozoic age zircon grains in proterozoic strata resting on tarim basement yielded mainly 2 0 1 9 ga ages whereas proterozoic strata of the qaidam and qilian terranes yielded mainly ca 930 820 ma and ca 1 9 1 1 ga ages the younger grains were apparently shed from local igneous rocks whereas the grains older than 1 1 ga were shed from an undetermined continental source grains in the lower paleozoic strata are mainly ca 500 430 ma and were shed from nearby plutonic and possibly volcanic rocks that formed in a magmatic arc setting our detrital zircon ages are consistent with a model first proposed by e r sobel and n arnaud in which early paleozoic magmatism occurred within a single northeast facing magmatic arc that was constructed across an assemblage of middle to late proterozoic accretionary complexes remnants of magmatic arcs and shallow marine strata this arc system was accreted to the tarim and sino korean cratons during silurian devonian time the resulting suture has been reactivated as tertiary thrust faults that currently define the structural and topographic margin of the tibetan plateau our data also provide two new estimates for the offset along the eastern altyn tagh fault a belt of middle proterozoic shallow marine strata is offset by 400 km whereas a belt of 490 480 ma magmatic arc rocks is offset by 370 km these values are generally similar to the 350 400 km offset reported in most previous studies

seismic tomography studies of cover thickness and near surface bedrock velocities reflection seismic imaging of the uppermost kilometer of crystalline bedrock is an important component in site surveys for locating potential storage sites for nuclear waste in sweden to obtain high quality images refraction statics are calculated using first break traveltimes these first break picks may also be used to produce tomographic velocity images of the uppermost bedrock in an earlier study we presented a method applicable to data sets where the vast majority of shots are located in the bedrock below the glacial deposits or cover typical for northern latitudes a by product of this method was an estimate of the cover thickness from the receiver static that was introduced to sharpen the image we now present a modified version of this method that is applicable for sources located in or on the cover the general situation for nuclear waste site surveys this modified methodalso solves for 3d velocity structure and static correctionssimultaneously in the inversion process the static correcti

cross well seismic waveform tomography for monitoring co2 injection a case study from the ketzin site germany seismic full waveform inversion waveform tomography is a method to reconstruct the underground velocity field in high resolution using seismic data the method was first introduced during the 1980 s and became computationally feasible during the late 1990 s when the method was implemented in the frequency domain this work presents three case studies and one synthetic benchmark of full waveform inversion applications two of the case studies are focused on time lapse cross well and 2d reflection seismic data sets acquired at the ketzin co2 geological storage site these studies are parts of the co2sink and co2man projects the results show that waveform tomography is more effective than traveltime tomography for the co2 injection monitoring at the ketzin site for the cross well geometry for the surface data sets we find it is difficult to recover the true value of the velocity anomaly due to the injection using the waveform inversion method but it is possible to qualitatively locate the distribution of the injected co2 the results agree well with expectations based upon conventional 2d cdp processing methods and more extensive 3d cdp processing methods in the area a further investigation was done to study the feasibility and efficiency of seismic full waveform inversion for time lapse monitoring of onshore co2 geological storage sites using a reflection seismic geometry with synthetic data sets the results show that waveform inversion may be a good complement to standard cdp processing when monitoring co2 injection the choice of method and strategy for waveform inversion is quite dependent on the goals of the time lapse monitoring of the co2 injection the last case study is an application of the full waveform inversion method to two crooked profiles at the forsmark site in eastern central sweden the main goal of this study was to help determine if the observed reflections are mainly due to fluid filled fracture zones or mafic sills one main difficulty here is that the profiles have a crooked line geometry which corresponds to 3d seismic geometry but a 2d based inversion method is being used this is partly handled by a 3d to 2d coordinate projection method from traveltime inversion the results show that these reflections are primarily due to zones of lower velocity consistent with them being generated at water filled fracture zones

waveform tomography of field vibroseis data using an approximate 2d geometry leads to improved velocity models waveform tomography a combination of traveltime tomography or inversion and waveform inversion is applied to vibroseis first arrival data to generate an interpretable model of p wave velocity for a site in the nechako basin south central british columbia canada we use constrained 3d traveltime inversion followed by 2d full waveform inversion to process long offset 14 4 km first arrival refraction waveforms resulting in a velocity model of significantly higher detail than a conventional refraction statics model generated for a processing workflow the crooked line acquisition of the data set makes 2d full waveform inversion difficult thus a procedure that improves the tractability of waveform tomography processing of vibroseis data recorded on crooked roads is developed to generate a near surface 2 km velocity model for the study area the data waveforms are first static corrected using a time shift determined by 3d raytracing which accounts for the crossline offsets produced by the crooke

gently dipping fracture zones in paleoproterozoic metagranite sweden evidence from reflection seismic and cored borehole data and implications for the disposal of nuclear waste 1 the svecokarelian orogen in the coastal area north of stockholm central sweden is characterized by a complex deformation belt in this belt bedrock domains strike wnw nw dip steeply and are affected by high ductile strain these domains anastomose around tectonic lenses that are up to a few tens of kilometers in length and are a few kilometers wide the bedrock within the lenses is folded and in general affected by lower ductile strain site investigations for the disposal of highly radioactive nuclear waste are presently in progress within one of these lenses approximately 16 km of high resolution 10 m source and receiver spacing 100 channels seismic data were acquired in 2002 along five separate profiles 2 to 5 km in length within this lens in the southeast reflection orientations are well determined where profiles cross one another here there is a nearly one to one correlation of distinct reflections on the seismic sections with hydraulically conductive fracture zones in cored boreholes indicating that these fracture zones control the reflectivity however smaller lenses of amphibolite within the fracture zones may enhance the reflectivity the reflections dip gently to the sse and se and the zones in the boreholes are dominated by fractures that show the same dip direction or are subhorizontal a working hypothesis for the gently dipping fracture zones suggests that these structures formed as minor thrust faults during the later stages of the svecokarelian orogeny mineral fillings and coatings along fractures in these zones indicate later reactivation the current stress field a high intensity of fractures in the zones at a high angle to 3 high in situ stresses in the bedrock and rapid glacial unloading with the development of high differential stresses may explain the large volume of groundwater in these zones the reflection seismic data in combination with the verifying work presented in the cored borehole data have steered the subsequent focus in geoscientific studies to the northwestern part of the candidate area

detrital zircons reveal no jurassic plateau in the eastern north china craton abstract u pb hf isotopic analyses have been carried out on detrital zircons from late permian jurassic strata in the western shandong bohai bay wsbb basins with aims of constraining the paleogeography and evolution of the eastern north china craton ncc four major groups of u pb ages namely 3 0 2 3 ga 2 2 1 4 ga 1250 430 ma and 410 150 ma are recognized for zircons from the fine grained sandstones the post paleoproterozoic zircons of the late permian sample show an age cluster of 344 255 ma with e hf t values of 18 to 8 being similar to those extracted from late paleozoic igneous rocks from the yinshan yanshan orogenic belt yyob on the northern margin of the ncc however the devonian jurassic zircons 390 150 ma from the jurassic sediments have e hf t values from 45 to 14 very similar to the mixture of phanerozoic zircons from the xing meng orogenic belt xmob and the yyob but significantly different from those of the liaodong peninsula jiaodong peninsula and the western shandong uplift in addition cambrian silurian zircons 535 430 ma of the jurassic samples have e hf t values from 27 to 7 resembling the early paleozoic zircons extracted from the northern qinling orogen nqo the u pb age spectra and hf isotope of devonian jurassic zircons as well as bulk nd isotopes suggest that the central eastern ncc received some juvenile materials from the xmob the yyob and the nqo during the jurassic this indicates widespread prototype basins and a low elevation during the jurassic arguing against the presence of a paleo plateau in the eastern ncc at that time the lack of evidence predicted by lithospheric delamination e g large scale elevation or doming after late triassic makes the delamination unlikely to be a viable mechanism of lithospheric thinning of the ncc the subsidence rather than elevation of the eastern ncc after late triassic might be related to thermo chemical erosion of the lithosphere by underlying convective mantle in a back arc setting

micromorphology of soils and palaeosoils in belgium an inventory and meta analysis abstract a study of the literature dealing with micromorphology of belgian soils and palaeosoils is presented most soils in belgium developed in quaternary covers sandy in the north becoming more silty towards the south and mixed with more or less important amounts of substrate material in addition azonal soils occur in the recent dunes the marine polders and the alluvial areas the main pedogenic micromorphological characteristics are bioturbation clay illuviation features in the more silty materials and spodic features in the more sandy materials glauconite plays an important role in pedogenesis throughout most profiles features related to a sub recent pedogenic environment are recognised pointing to polygenetic soil formation impact of periglacial conditions is often visible bog ores in alluvial plains have a complex mineralogical composition and microfabric buried palaeosoils and soil sediments are discussed separately according to their age whereas polygenetic soils are treated together with the recent soils according to their geographic position for some areas e g the polders the sandy area of flanders and the pays de gaume in the southernmost part of belgium only little micromorphological information is available most soils studied were situated under natural vegetation studies of cultivated soils are rather rare

detrital zircon u pb ages of middle late permian sedimentary rocks from the southwestern margin of the north china craton implications for provenance and tectonic evolution abstract the southwestern margin of the north china craton ncc is located between the alxa terrane to the northwest the north qilian orogen to the west and the north qinling orogen to the south however the paleogeographic and tectonic evolution for the southwestern part of the ncc in the late paleozoic is still poorly constrained in order to constrain the late paleozoic tectonic evolution of the southwestern ncc we carried out detailed field work and detrital zircon u pb geochronological research on middle late permian sedimentary rocks at the southwestern margin of the ncc the u pb age spectra of detrital zircons from six samples are similar showing four populations of 2 6 2 4 ga 2 0 1 7 ga 500 360 ma and 350 250 ma moreover on the basis of the weighted mean age of the youngest detrital zircons 257 4 ma combined with the published results and volcanic interlayers we propose that the shangshihezi formation formed during the middle late permian our results and published data indicate that the detrital zircons with age groups of 2 6 2 4 ga and 2 0 1 7 ga were likely derived from the khondalite belt and yinshan block in the northwestern ncc the junction part between the north qinling and north qilian orogen may provide the 500 360 ma detrital zircons for the study area the 350 250 ma detrital zircons were probably derived from the northwestern part of the ncc the majority of materials from shangshihezi formation within the study area were derived from the northwestern part of the ncc indicating that the northwestern part of the ncc was strongly uplifted possibly resulting from the progressive subduction and closure of the paleo asian ocean a small amount of materials were sourced from southwestern part of the ncc indicating that the north qinling orogen experienced a minor uplift resulting from the northward subduction of the south qinling terrane

reflection seismic waveform tomography 1 in seismic waveform tomography if using reflection data with limited source receiver offsets it is difficult to reconstruct the deep part of the subsurface velocity model we present two approaches to tackle this problem layer stripping and weighted updating in a layer stripping procedure we replace the top portion of seismic data with synthetics generated from the previous layer inversion and make the current inversion focus on the minimization of the data misfit corresponding to the deep part of the model to improve efficiency we use only sparsely sampled frequency data in the deeper layer inversions unlike the first layer inversion where we use densely sampled frequency data as usual the sparsely sampled frequencies together have the full wave number coverage for effective imaging combined use of dense and sparse sampling in frequency is a compromise between resolution and efficiency as it reduces the number of iterations needed in layer stripping inversion while still producing a good image in the second scheme we apply depth dependent weights to model updates in order to improve the convergence in an iterative solution the weighting is inversely proportional to the ray density variation along the depth and is mathematically equivalent to the application of an inverse hessian matrix which sharpens the gradient vector for model updating for real seismic data we transfer point source shot records to line source records by partial amplitude compensation and phase adjusting before inputting it to the waveform tomography we perform traveltime inversion to generate a reliable layered velocity model and then waveform tomography to produce a high resolution image of the subsurface model through frequency domain iteration

mesozoic contractional deformation in the middle of the asian tectonic collage the intraplate western ordos fold thrust belt china abstract intraplate deformation can occur at great distances from synchronous plate boundaries and is most likely the result of strain concentrations into weak zones these weak zones may be pre existing crustal heterogeneities such as faults thermally weakened zones due to magmatism and or the effects of a thick sedimentary cover or mechanical contrasts between adjacent crustal blocks intraplate deformation is not exclusively related to continent continent collision it can be the result of a change in subduction dynamics or the interaction of two convergent plate boundaries asia has many examples of active intraplate deformation that are thought to be related to the cenozoic indo asian collision although much attention is placed on active examples discerning controls on pre cenozoic asian intraplate deformation will lead to not only a better understanding of the processes involved in intraplate orogens but also the tectonic evolution of asia situated on either side of the yellow river along the western margin of the ordos plateau the intraplate western ordos fold thrust belt involves units as old as archean basement and as young as late jurassic the fold thrust belt is spectacularly exposed in two ranges the helan shan and the zhuozi shan cross sections drawn through the north trending fold thrust belt suggest 30 minimum shortening a paleocurrent reversal within the lower middle jurassic section is interpreted to mark the onset of contraction and mountain building a late jurassic synorogenic boulder conglomerate records the final deformation in the fold thrust belt synchronous with contraction and cutting across the fold thrust belt is an e w striking strike slip fault that displays right lateral drag and sub horizontal striae we interpret this fault as an accommodation structure in the thrust belt following e w contraction the thrust belt was dismembered by an n15 w trending left lateral strike slip fault the left lateral fault displaces the frontal portion of the thrust belt the zhuozi shan 62 km to the north relative to a more internal portion the helan shan we propose that the anomalous orientation and intraplate location of the western ordos fold thrust belt is a function of mechanical contrasts between a previously deformed area and a stable crustal block ordos to the east pre existing crustal weakness or anisotropy along the western margin of the ordos block is most likely related to either a late proterozoic early paleozoic aulacogen a triassic fault system or to both although its intraplate location and the complexities of mesozoic asian plate interactions make it difficult to relate deformation in the western ordos fold thrust belt to a specific contemporaneous plate boundary its n s trend may suggest a link with paleo pacific subduction along the eastern margin of asia

three dimensional imaging of the p and s wave velocity structure and earthquake locations beneath southwest iceland three dimensional imaging of the p and s wave velocity structure and earthquake locations beneath southwest iceland