imaging of erebus volcano using body wave seismic interferometry of strombolian eruption coda 1 seismic interferometry is a recently developed theory that allows for the recovery of a medium s impulse response between two points should randomly distributed sources of white noise or equivalently a multiply scattered equipartioned wavefield be present throughout the medium we exploit the extremely scattering nature of volcanic media and seismic illumination from impulsive strombolian eruptions to extract single station body wave green s tensors at an unusually dense array of stations on erebus volcano antarctica we optimally rotate these green s tensors for each notable arrival and back project them to construct a 3 dimensional scattering map of the magma filled volcano conduit system also corroborated by an independent active source tomography experiment using the same station distribution this approach not only favors highly scattering media contrarily to most conventional methods but its passive nature i e non anthropogenic sources allows for studies of structural temporal variability and possible extension into real time monitoring of active volcanoes

offscraping accretion of jurassic chert clastic complexes in the mino tamba belt central japan abstract detailed structural and biostratigraphical analysis of the jurassic inuyama sequence a coherent chert clastic complex in the mino tamba belt central japan clarifies the evolution of accretionary processes at shallow structural levels the inuyama sequence is characterized by a series of stacked thrust sheets each sheet consists of an early triassic to middle jurassic oceanic plate stratigraphy composed of four lithologic units which are in ascending order siliceous claystone ribbon chert siliceous mudstone and clastic rocks the structural features of the inuyama sequence demonstrate a four stage progressive deformation 1 a decollement was initiated within the siliceous mudstone when this sequence was just seaward of the deformation front clastic dikes and sills formed at the horizon just above the decollement at this time 2 the stratigraphic section above the decollement was imbricated by in sequence thrusting in the frontal part of the wedge this initial stage of thrusting and imbrication was followed by 3 the formation of duplex structures with fault related folds within the lower stratigraphic section as the decollement stepped down section to the lowest siliceous claystone interval finally 4 these thrust packages were overprinted by secondary prism thickening in the form of out of sequence thrust faulting

deposits of high density turbidity currents on fan delta slopes an example from the upper visean szczawno formation intrasudetic basin poland abstract the sedimentary succession of the szczawno formation upper visean intrasudetic basin comprises several lithofacies which reflect different transport deposition mechanisms six facies associations interpreted as deposits of 1 alluvial delta plain 2 fan delta front 3 prodelta 4 subaqueous fan 5 basin plain and slope and 6 shallow marine shelf are distinguished coarse grained fan delta front deposits form large scale several tens of metres thick and 2 3 km in cross section lensoidal bodies enveloped by fines of prodeltaic to basin plain settings they represent channel and lobe complexes developed on frontal faces of fan deltas which entered the submerged intramontane basin from the north fan deltas evolved from alluvial fans built along tectonically active steep northern basin slope sedimentation on the delta fronts was dominated by gravity flows most sediments deposited from gravelly and or sandy high density turbidity currents the sediments display a diverse suite of facies related to variable flow parameters sediment concentration grain size velocity slope gradient etc sedimentary units commonly amalgamate which is explained in terms of surging nature of flows the growth of the fan deltas ceased due to rejuvenation uplift of the southern edge of the basin which caused a northeastward progradation of a large fluvial deltaic system and consequently a marine regression

shallow geology of the northern barents sea implications for petroleum potential the shallow geology of the northern barents sea has been studied through analyses of geophysical data and geological samples from gravity cores mesozoic rocks subcrop in the entire study area with triassic middle jurassic rocks dominating the shallowest and western part of the area and upper jurassic lower cretaceous rocks dominating the central areas a palynologically investigated sample representing in situ bed rock gives an aptian early albian age indicating that lower cretaceous units dominate the eastern part of the study area these beds were deposited during shallow marine conditions and show a petrographic composition comparable to the carolinefjellet formation of svalbard the thickness of the lower cretaceous section is almost 1000 m organic geochemical analyses of the aptian lower albian rocks suggest a post early cretaceous erosion of a maximum of 2000 m an important tectonic event in the region was a compressive phase near the cretaceous tertiary boundary occurrences of porous well sorted lower cretaceous sandstones succeeding organic rich mature upper jurassic and lower cretaceous shales sealed by lower cretaceous shales within antiform settings represent interesting play concepts in the study area the petroleum potential has been limited by the post early cretaceous uplift and erosion resulting in the termination of hydrocarbon generation followed by gas expansion

very long period oscillations of mount erebus volcano as the signal decays vlp scalar moments up to 5 10 11 n m exceed sp moments by an order of magnitude or more suggesting distinct though genetically related sp and vlp source mechanisms we conclude that vlp signals arise from excitation of a quasi linear resonator that is intimately associated with the conduit system and is excited by gravity and inertial forces associated with gas slug ascent eruption and magma recharge vlp signal stability across hundreds of eruptions spanning 5 years the persistence of the lava lake and the rapid posteruptive lava lake recovery indicate a stable near summit magma reservoir and vlp source process index terms 4544 oceanography physical internal and inertial waves 7280 seismology volcano seismology 8419 8414 volcanology eruption mechanisms 8419 volcanology eruption monitoring 7280 keywords strombolian very long period volcano seismology

earthquake induced sediment failures on a 0 25 slope klamath river delta california on november 8 1980 a major earthquake magnitude 6 5 to 7 2 occurred 60 km off the coast of northern california a survey of the area using high resolution seismic reflection and side scan sonar equipment revealed the presence of extensive sediment failure and flows in a zone about 1 km wide and 20 km long that trends parallel to the shelf on the very gently sloping c and a prominent 1 to 2 m high seaward facing toe scarp on the outer margin of the terrace this toe scarp is sinuous appears to be nearly continuous for a distance of 20 km and closely parallels the 60 m isobath evidence indicates that the toe scarp is the terminus of lateral spreads and lobes of sediment flows side scan sonar records show evidence of gas vents and small 10 3 0 5 m high pressure ridges formed seaward of and parallel to the sediment flow scarp indicators of liquefaction sand boils and collapse craters are present on the sediment flow terrace extensive sediment failure occurred on a sea floor slope of less than 0 25 and we can unequivocally pinpoint the cause as an earthquake of known location magnitude and time

transition from storm wave dominated outer shelf to gullied upper slope the mid pliocene orinoco shelf margin south trinidad shelf edge deltas are a key depositional environment for accreting sediment onto shelf margin clinoforms the moruga formation part of the palaeo orinoco shelf margin sedimentary prism of south east trinidad provides new insight into the incremental growth of a pliocene storm wave dominated shelf margin relatively little is known about the mechanisms of sand bypass from the shelf break area of margins and in particular from storm wave dominated margins which are generally characterized by drifting of sand along strike until meeting a canyon or channel the studied st hilaire siltstone and trinity hills sandstone succession is 260 m thick and demonstrates a continuous transition from gullied with turbidites uppermost slope upward to storm wave dominated delta front on the outermost shelf the basal upper slope deposits are dominantly mass transport deposited blocks as well as associated turbidites and debrites with common soft sediment deformed strata the overlying uppermost slope succession exhibits a spectacular set of gullies which are separated by abundant slump scar unconformities tops of rotational slides then filled with debris flow conglomerates and sandy turbidite beds with interbedded mudstones the top of the study succession on the outer shelf area contains repeated upward coarsening sandstone rich parasequences 2 to 15 m thick with abundant hummocky and swaley cross stratification clear evidence of storm swell and storm wave dominated conditions the observations suggest reconstruction of the unstable shelf margin as follows i the aggradational storm wave dominated shelf edge delta front became unstable and collapsed down the slope ii the excavated scars of the shelf margin became gullied but gradually healed aggraded by repeated infilling by debris flows and turbidites and then new gullying and further infilling and iii renewed storm wave dominated delta front prograded out across the healed outer shelf re establishing the newly stabilized shelf margin the moruga formation study along with only a few others in the literature confirms the sediment bypass ability of storm wave dominated reaches of shelf edges despite river dominated deltas being by far the most efficient shelf edge regime for sediment bypass at the shelf break this article is protected by copyright all rights reserved

analysis of structural trends of sub sea floor strata in the isfjorden area of the west spitsbergen fold and thrust belt based on multichannel seismic data a dense grid of 2d multichannel seismic data was used for the interpretation of sub sea floor structures in the area of isfjorden in western spitsbergen west spitsbergen underwent eocene transpressional deformation that resulted in formation of the west spitsbergen fold and thrust belt three horizons were defined for the seismic interpretation as well expressed and continuous reflections 1 the top of the metamorphic basement 2 the base of the upper carboniferous nordenskioldbreen formation 3 the base of the lower cretaceous helvetiafjellet formation time structure maps and analysis of the sub bottom structural trends were generated for each horizon the top of the metamorphic basement displays north south trending graben structures apparently representing continuation of the devonian grabens from northern spitsbergen the tectonostratigraphic unit bounded by the base of the upper carboniferous nordenskioldbreen formation and base of the helvetiafjellet formation encloses the fold and thrust belt and is affiliated with wsw ene shortening involving three decollement levels within this unit the strata between the middle triassic shales and upper upper jurassic shales decollements have undergone the most intense strain whereas sediments situated between the basal lower permian evaporites and middle decollements underwent a relatively mild deformation the strata above the base of the helvetiafjellet formation are characterized by minor tertiary deformation only

autocorrelation of the seismic wavefield at newberry volcano reflections from the magmatic and geothermal systems we show that seismic autocorrelations provide new depth constraints on upper crustal magmatic systems autocorrelations of both ambient noise recorded on seismometers and geophones and teleseismic earthquake coda recorded on seismometers elucidate the structure of newberry volcano these autocorrelations result in the two way body wave green s function beneath a station within the caldera a reproducible coherent p wave reflection is inferred to come from the top of a magma body at 2 5 km depth and maps with the lateral extent of an anomalously low velocity body imaged tomographically on the west flank of the volcano a reflection that deepens with distance from the caldera is inferred to result from a temperature dependent change in metamorphic facies and may map the thermal structure of the edifice our results show that the autocorrelation of diffuse seismic energy reconstructs reflections from seismically sharp boundaries associated with the upper crustal magmatic structure

the seismic facies of a tidally influenced holocene delta boundary bay fraser river delta b c abstract the tidally influenced fraser river delta in southwestern british columbia is actively prograding into the strait of georgia to investigate the geometry stratigraphy and structure of the post glacial fraser river delta sediments a high resolution shallow seismic reflection survey was carried out during the summer of 1987 in the boundary bay region of the delta twenty kilometers of optimum offset seismic reflection data were collected these high resolution seismic profiles were shot with 3 m spacing between geophones and a two way travel time of 200 ms four seismic facies were identified representing foreset topset slope failure and distributary channel deposits the foreset seismic facies has reflections that dip at angles of 1 to 7 towards boundary bay along strike the reflections have horizontal or mounded patterns horizontal continuous reflections typify the topset seismic facies the slope failure facies is located within the foreset seismic facies and consists of upper convex reflections and broken internal reflections the distributary channel seismic facies is characterized by concave downward reflections and is incised into the top of the foreset facies

sedimentary facies of the nova scotian upper and middle continental slope offshore eastern canada a detailed survey of the upper and middle nova scotian continental slope at 42 50 n and 63 30 w indicates a complex morphology dominated by mass movements on various scales and an immature turbidity current channel the range of sediment facies is diverse including hemipelagic and turbidite muds turbidite sands and gravelly sandy muds of debris flow origin deformed units interpreted as slump deposits are also observed several facies associations related to discrete morphological environments are recognized thick turbidite sand units with minor intervening mud beds are characteristic of the high relief uppermost slope and channel margin thinner turbidite sands deformed slump beds and various mud facies are associated with small scale hummocky mid slope topography sand beds are more abundant in the depressions than on intervening hummocks indicating the preferred transport paths of small turbidity currents at the lower end of the main turbidity current channel frequent turbidite sand beds with relatively minor mud beds are deposited on a depositional lobe in areas unaffected by mass movements alternating bioturbated mud and sandy muds make up the core sequences a local model of sedimentation is proposed for this area and illustrates that simple models of continental slope sedimentation only apply to a limited range of settings

shallow bedrock geology of the olga basin area northwestern barents sea 1 the east west trending olga basin has possibly the largest post jurassic sedimentary rock thickness in the northwestern barents sea the thickness of these mainly shallow marine deposits exceeds 750 m in the study area and increases eastward the olga basin is characterized by relatively undisturbed layers which except for local areas rarely dip more than 3 degrees the storbanken area is heavily penetrated by normal faults which probably are related to the late cretaceous uplift in the region differential uplift along the flanks of the olga basin during the oxfordian hauterivian led to deposition of onlapping units in the central parts whereas erosion and limited deposition prevailed on the topographic highs the overlying barremian sequence is more uniform and is t least 350 m thick in the hammerfest basin in the southern barents sea corresponding barremian deposits are found the post jurassic strata contain sandstones of three different kinds subarkose sublitharenite litharenite and lithic arkose the barremian subarkoses sublitharenites have relatively high porosities and may be potential reservoir rocks the organic geochemistry analyses show somewhat higher hydrogen index values than those found in the corresponding sedimentary strata on spitsbergen however the strata are slightly less mature than the corresponding strata on spitsbergen

analysing the origin of the upper cretaceous lower tertiary rio capim semi flint para state brazil under a sedimentologic perspective abstract the rio capim kaolin one of the largest kaolin reserves in the world currently under exploration is typified by a lower and an upper unit represented of a soft well structured kaolin and a semi flint kaolin respectively the latter term been applied here for a flint like fire clay consisting of indurated kaolinite which develops no plasticity when ground up the latter is characterized by its elevated hardness and massive nature which has been preliminarily attributed to stronger weathering relative to the underlying soft kaolin despite the overall massive aspect a detailed sedimentologic investigation of freshly exposed sections along open mines revealed a variety of structures in the semi flint kaolin that are attributed to primary sedimentary features the features include channel like forms having distinct lags of quartz sandstones at their bottoms these deposits intergrade with strata displaying a series of inclined lines defining lobed bodies that are locally highlighted by distinctively soft massive mud layers the lobes are internally truncated by undulating surfaces attributed to wave erosion the features described in this work are related to deposition of the semi flint kaolin unit in either distributary channels and mouth bar or tidal inlet and tidal delta areas associated with deltaic or wave dominated estuarine settings respectively the recognition of these deposits in the semi flint unit has large implications to analyze its composition which must have primarily included sand grain sizes at least in the case of the lobed strata the apparent muddy nature of the semi flint kaolin might be due at least in part to post depositional modification of a sandy unit composed most likely by grains of previously formed kaolinite derived from reworking of the underlying soft kaolin unit

the energy partitioning and the diffusive character of the seismic coda following recent theoretical developments of the radiative transfer the ory of elastic waves we propose to use the ratio r of energies of curl and divergence part of the ground displacement to distinguish between the different possible domi nant scattering regimes in the lithosphere a consequence of the diffusion regime is the partitioning of the energy between different vibrational modes which is inde pendent of time it results in the stabilization of r this behavior is not expected if low order diffraction such as single scattering is dominant we apply our technique to seismograms recorded by a small aperture seismic array operated during june august 1997 in guerrero mexico we estimate the energy ratio r in the coda of 13 earthquakes recorded by the array we find it to be very stable in the coda window while the energy level itself changes by several orders of magnitude the value of r is 7 1 independent of the earthquake location and the magnitude the observed stabilization of r is a strong indication of the diffusive regime of the seismic coda

growth faults at the prodelta to delta front transition cretaceous ferron sandstone utah cliff exposures of synsedimentary growth faults at the base of the cretaceous ferron sandstone in central utah represent outcrop analogs to subsurface growth faults delta front sands prograded over and deformed less dense prodelta muds of the underlying tununk shale detailed fault patterns and associated facies changes demonstrate a complex fault history and style for growth fault development rather than a simple progressive development of faults in a basinward position the most proximal and most distal fault sets were the earliest active faults growth faulting was initiated by deposition of cross bedded distributary channel and mouth bar sandstones that reach 9 m thick in the hangingwalls of the faults curvature of the beds in the hangingwall of the faults nucleates smaller conjugate fault sets cross bed sets in the hangingwalls of faults decrease from meter to decimeter scale away from the faults suggesting decreasing flow velocity or decreased preservation of cross sets as a result of decreasing accommodation in distal hangingwalls shifts in depositional loci including upstream and downstream accretion of mouth bar sands contribute to the complex faults history and internal heterogeneity and development of potentially isolated sandy reservoir compartments

multiple scattering from icequakes at erebus volcano antarctica implications for imaging at glaciated volcanoes we examine seismic coda from an unusually dense deployment of over 100 short period and broadband seismographs in the summit region of mount erebus volcano on a network with an aperture of approximately 5 km we investigate the energy partitioning properties of the seismic wavefield generated by thousands of small icequake sources originating on the upper volcano and use them to estimate green s functions via coda cross correlation emergent coda seismograms suggest that this locale should be particularly amenable to such methods using a small aperture subarray we find that modal energy partition between s and p wave energy between 1 and 4 hz occurs in just a few seconds after event onset and persists for tens of seconds spatially averaged correlograms display clear body and surface waves that span the full aperture of the array we test for stable bidirectional green s function recovery and note that good symmetry can be achieved at this site even with a geographically skewed distribution of sources we estimate scattering and absorption mean free path lengths and find a power law decrease in mean free path between 1 5 and 3 3 hz that suggests a quasi rayleigh or rayleigh gans scattering situation finally we demonstrate the existence of coherent backscattering weak localization for this coda wavefield the remarkable properties of scattered seismic wavefields in the vicinity of active volcanoes suggests that the abundant small icequake sources may be used for illumination where temporal monitoring of such dynamic structures is concerned

source depopulation potential and surface wave tomography using a crosscorrelation method in a scattering medium we use seismic prospecting data on a 40 40 regular grid of sources and receivers deployed on a 1 km 1 km area to assess the feasibility and advantages of velocity analysis of the shallow subsurface by means of surface wave tomography with green s functions estimated from crosscorrelation in a first application we measure rayleigh wave dispersion curves in a 1d equivalent medium the assumption that the medium is laterally homogeneous allows using a simple projection scheme and averaging of crosscorrelation functions over the whole network because averaging suppresses noise this method yields better signal to noise ratio than traditional active source approaches and the improvement can be estimated a priori from acquisition parameters we find that high quality dispersion curves can be obtained even when we reduce the number of active sources used as input for the correlations such source depopulation can achieve significant reduction in the cost of active source acquisition in a second application we compare rayleigh wave group velocity tomography from raw and reconstructed data we can demonstrate that the crosscorrelation approach yields group velocity maps that are similar to active source maps scattering has an importance here as it may enhance the crosscorrelation performance we quantify the scattering properties of the medium using mean free path measurements from coherent and incoherent parts of the signal we conclude that for first order velocity analysis of the shallow subsurface the use of crosscorrelation offers a cost effective alternative to methods that rely exclusively on active sources

architecture and facies pattern of a sublacustrine fan jharia basin india abstract a small sublacustrine fan deposit has been identified within a lacustrine succession belonging to the barren measure formation middle permian of the lower gondwana deposits of jharia basin india the stratigraphic position of the fan and its structural relationship with the associated sediments suggest that the east west aligned elongate trough formed in the central part of the basin experienced intrabasinal normal faulting of limited lateral extent and accumulation of clastic input within the associated hangingwall syncline led to formation of this deposit three major framework components can be identified within this deposit a sheet like sandstone aprons b channel fill sandbodies and c lensoid massive beds of pebbly sandstone the laterally extensive sheet like bodies of sandstone covering almost the whole of the older sediments appear to be the product of deposition from unconfined sediment laden flows during episodic flood events the proximal part of the deposit is dominated by the successive deposition of sandstone aprons with a few channel plug sandbodies produced through rapid sedimentation from channelised sediment laden turbulent flows the distal part on the other hand is mainly represented by the stacked channel fills with alternate sandstone aprons following the deposition of bedded sandstones as the slope of the depositional surface reduced turbulent flows with relatively less grain concentration extended towards the ambient waterbody through channels incised into the preexisting unconsolidated sediments during this process of incision the flows gradually became hyperconcentrated the channels were ultimately filled in by concordant bedsets in approximate conformity with the shape of the channel either through bedload deposition or suspension fall out from these submerged currents a few massive channel fills indicating emplacement of liquefied sandflows caused by slope instability during high flood event are also present isolated channel fills show lateral uniformity in facies pattern while confluent channels produced laterally variable composite facies association with a distinct zone of interference lensoid mass flow deposits with distinct upslope slide scarps represent the event of slope failure as a result of cannibalisation during low water stand these slide lenses are present in different levels in association with either the sandstone aprons or the channel fills showing high degree of randomness in their order of appearance the consistently developed round bottomed geometry of the channels and the nature of channel fills strongly advocate in favour of their subaqueous origin absence of any subaerial character within the sandstone aprons also suggests their emplacement under subaqueous condition the thick stacks of channel fill sandbodies were developed as a consequence of vertical channel aggradation under continued hangingwall subsidence and the upward declining trend in vertical aggradation suggests gradual fall in the rate of this subsidence subsequently the whole block subsided and went under deepwater condition due to lacustrine transgression and the fan was buried under deepwater carbonaceous shale

synthetic seismic illumination of small scale growth faults paralic deposits and low angle clinoforms a case study of the triassic successions on edgeoya nw barents shelf abstract fault activity and sandstone body geometries and spread all bear significant weight to understanding the potential hydrocarbon systems on the nw barents shelf synthetic seismic modelling of onshore sedimentary successions provides insight into the seismic resolution and expression of various sedimentological features on edgeoya i sandy growth basins in pro delta mudstones ii paralic sedimentary deposits and iii low angle tidally influenced progradational successions synthetic modelling suggests that the lithological contrast associated with sand infilled growth basins in pro deltaic shales even with offsets as small as 50 75 m will create distinct geometries in seismic data modelling suggests that while optimal 90 illumination low frequency bands and more typical sedimentary velocities around 2000 m s will generate very clear discernible growth faults the angular lithological contrast should generate discernible features even with the high velocities and typical 20 30 hz frequency band of seismic sections on the nw barents shelf comparing to actual seismic data in which multiples noise and in places overburden are influential it is possible to identify growth fault geometries more confidently and to link them to larger planar fault activity modelling other features identified in the paralic sedimentary system it is apparent that many of the massive channel or lenticular shaped sandstone bodies should be identifiable in the actual seismic although their expression is less distinct and more easily misinterpreted than that of growth faults it is apparent that features such as igneous intrusions unless imaged in a perfect survey can be difficult to properly identify particularly near vertical connections the velocity contrast creates strong impedance along horizontal sections but heavily fractured igneous intrusions with lower velocities could easily be assumed to be isolated sandstone bodies while the modelling appreciates the overall wedging nature of the successions the simplified lithological observations onshore cannot predict the probable erosion condensation contrast associated with low angle clinoforms which are visible in the seismic data and hence not reproduce them easily in the models

sedimentology and depositional setting of the dartmouth group bigbury bay south devon the lower devonian dartmouth group records some of the earliest stages in the evolution of the variscan basins of southwest england this thick mudstone dominated group has previously been interpreted as distal fluvial sediments deposited on a coastal mudplain the sequence at bigbury bay is made up of two large scale sedimentary cycles the base of each cycle consists of pebbly mudstones graded siltstones and sandstones massive mudstones and heterolithic sediments with sporadic phosphatic nodules these facies were deposited in substantial lakes they were modified by phases of syn sedimentary deformation which generated subaqueous debris flows and turbidites the overlying parts of the cycle making up the bulk of the succession consist of mudstone and thin sheet like sandstones these are fluvial and were probably deposited in mud dominated terminal fans each cycle represents a phase of rapid probably fault controlled subsidence followed by relative tectonic quiescence this behaviour may reflect pulses of rifting or extension in strike slip basins followed by thermal relaxation

lapse time dependent coda wave depth sensitivity to local velocity perturbations in 3 d heterogeneous elastic media in the context of seismic monitoring recent studies made successful use of seismic coda waves to locate medium changes on the horizontal plane locating the depth of the changes however remains a challenge in this paper we use 3 d wavefield simulations to address two problems first we evaluate the contribution of surface and body wave sensitivity to a change at depth we introduce a thin layer with a perturbed velocity at different depths and measure the apparent relative velocity changes due to this layer at different times in the coda and for different degrees of heterogeneity of the model we show that the depth sensitivity can be modelled as a linear combination of body and surface wave sensitivity the lapse time dependent sensitivity ratio of body waves and surface waves can be used to build 3 d sensitivity kernels for imaging purposes second we compare the lapse time behaviour in the presence of a perturbation in horizontal and vertical slabs to address for instance the origin of the velocity changes detected after large earthquakes

anatomy of collapsed and re established delta front in lower cretaceous of eastern spitsbergen gravitational sliding and sedimentation processes spectacular coastal cliff exposures in an early cretaceous deltaic succession near kvalvagen in eastern spitsbergen norwegian arctic show a variety of styles of gravity driven deformation and resedimentation associated with delta front progradation and instability the large scale collapse involved a distributary channel sand unit some 20 m thick and the underlying delta slope prodelta shaly heterolithics the deformation was essentially brittle whereby large blocks of the delta front succession slid and rotated its gross style involved two large cuspate tear away scars at least 1 1 5 km wide and 50 60 m deep separated by narrow remnant buttresses of in situ strata the basement in the region was tectonically active and the delta front failure was most likely sei mically triggered initial infill of the collapse scars involved slumps and debris flows derived from scar walls and locally from the sliding blocks themselves these deposits partly smoothed the local topography created by the slide blocks this early infill was followed by deposition of thin mainly muddy turbidites probably shed from the scar walls by small localized failure renewal of fluvial supply of sand led to the main infill of the scar depressions this stage involved effluent generated turbidites heterolithic and increasingly sandier turbidites and liquefied sandflows derived from unstable oversteepened distributary mouthbars the mouth bar systems eventually achieved stability and prograded across the infilled scars they were affected by periodic storm wave attack and sudden increa es of water depth the scar infill at that stage was subject to minor growth faulting possibly related to new seismic tremors

depositional systems and sequence stratigraphy of coarse grained deltas in a shallow marine strike slip setting the bohemian cretaceous basin czech republic deposits of coarse grained gilbert type deltas showing varying degrees of reworking of foresets by basinal currents were identified in middle turonian to early coniacian sandstones of the bohemian cretaceous basin the progradation of the deltaic packages earlier interpreted as large scale subaqueous dunes shelf ridges or subaqueous fault scarp accumulation terraces was controlled by high and low frequency relative sea level changes in a relatively slowly subsiding intracontinental strike slip basin end member types of the bohemian cretaceous coarse grained deltas are deep water deltas characterized by thick 50 80 m foreset packages with steep 10 30 foresets and shallow water deltas which deposited thin 15 m packages with foresets typically between 4 and 10 the differences in thickness and foreset slope angle were controlled predominantly by the accommodation available during progradation the depositional regime of the deltas was governed by i the fluvial input of abundant sand bedload with a minor proportion of gravel ii gravity flows most probably caused by liquefaction of the upper part of the unstable foreset slope and iii migration of sandy bedforms on the foreset slopes the bedform migration was driven by unidirectional currents of possible tidal origin individual foreset packages represent systems tracts or parts of systems tracts of depositional sequences a variety of stacking patterns of high frequency sequences exists in the basin caused by low frequency relative sea level changes as well as by local changes in sediment input because of generally low subsidence rates fluvial or beach topset strata were not preserved in the cases studied the absence of preserved fluvial facies which has been one of the main arguments against the fluvio deltaic origin of the sandstone bodies is explained by erosion of the topsets during transgression and their reworking into coarse grained lags of regional extent covering ravinement surfaces

re evaluating the paleogeography of the river dominated and wave influenced ferron notom delta southern central utah an integration of detailed facies architecture and paleocurrent analysis abstract this study re evaluates the paleogeography of a river dominated and wave influenced deltaic system in a single parasequence 6a of the cretaceous ferron sandstone south central utah which was previously interpreted as a typical asymmetric delta the conceptual asymmetric delta model of bhattacharya and giosan 2003 has been widely applied to interpret ancient deltaic systems however reconstructed paleogeographies relying on this conceptual model are commonly not scaled to the architectural elements which could possibly lead to inaccurate interpretations especially when data are relatively sparse the extensively exposed ferron sandstone outcrops provide an opportunity to demonstrate how detailed facies architecture work can be integrated with regional facies relationships to elucidate a properly scaled paleogeography seven facies associations fa are identified in parasequence 6a and are arranged into two distinctively different successions the river dominated succession consists of prodelta distal delta front proximal delta front and terminal distributary channel fa while the wave and storm dominated succession comprises offshore shelf lower shoreface and upper shoreface fa the river dominated succession is muddier and less bioturbated than the wave and storm dominated succession facies architecture analysis shows that the river dominated proximal delta front facies consists of mouth bar and terminal distributary channel elements that are not seen in the wave and storm dominated facies the scales of mouth bars and terminal distributary channels suggest that they are rather small features compared with the river dominated delta lobe which is incompatible with the simple bar elongation asymmetric delta model presented by li et al 2011 instead parasequence 6a is interpreted to be a valley fed river dominated symmetric delta protected from waves by an updrift barrier system which is analogous to the modern mongky river delta on the west coast of madagascar the progressive change in orientation of west directed mouth bars to north directed and east directed lobes around the periphery of the river dominated delta indicates a highly radial lafourche type delta moving away from the protection of the barrier system there is a gradual change from highly river dominated facies to increasingly wave and storm influenced facies toward the southeast due to the entrenched nature of the feeder river associated with an incised valley system the parasequence 6a delta was bifurcation dominated rather than avulsion dominated this study shows that it is critical to integrate detailed facies architecture analysis in order to reconstruct properly scaled paleogeographies and hypothesizes that stable bifurcation dominated deltas should be more common than avulsion dominated deltas in a lowstand delta system due to the entrenched nature of the feeding trunk river which inhibits avulsion

architecture of the tectonically influenced sobrarbe deltaic complex in the ainsa basin northern spain abstract the syn tectonic sobrarbe deltaic complex eocene of the ainsa basin spanish pyrenees is confined by lateral thrust ramps and influenced by intra basinal growth anticlines six facies associations have been distinguished within the deltaic complex i slope marls and turbidite sandstones ii distal delta front silty and bioturbated sandstones iii proximal delta front and delta plain deposits tidal inlet tidal flat mouth bar bay distributary channel and floodplain environments iv biogenic deposits at flooding surfaces v collapse zone sediments and vi nummulite dominated shallow marine carbonates the deltaic complex comprises four composite sequences which each contain a number of minor sequences of the genetic maximum flooding surface bounded type regressive unconformities and their correlative surfaces separate the composite sequences cs and each cs can be divided into lowstand transgressive and highstand components at the base the comaron cs is a wnw prograding deltaic complex containing six minor sequences characterized by basinward stepping sandstone wedges separated by transgressive mudstones double regressive unconformities are often associated with these sandstone wedges proximally in the basin growth of the intra basinal arcusa anticline caused gentle folding of the comaron cs and syn growth strata at the base of the overlying las gorgas cs contain a prominent forced regressive sandstone wedge the las gorgas sandbody and display thinning of bedsets onto the crest of the anticline moreover it can be demonstrated that relative sea level rise took place in the growth synclines at the same time as a fall in relative sea level occurred on the growth anticlines the tectonic deformation caused a shift in the direction of deltaic progradation towards the north northwest as demonstrated by the well developed clinoforms in the highstand sequence set of the las gorgas cs a second phase of tectonic activity this time triggering large scale collapse of the delta front occurred at the transition between the las gorgas and barranco el solano cs tilting of the basin floor led to the development of coeval transgressive and regressive strata separated by a fulcrum line of zero net vertical movement of the shoreline in the post tilt phase reduced sediment supply and accelerated subsidence led to widespread transgression and a change from clastic to carbonate dominated sedimentation this phase was terminated by a gradual increase in sediment supply causing progradation of a mixed clastic carbonate system dominated by large nummulite banks and bioturbated shoreface marls and sandstones finally a pronounced fall in relative sea level associated with the transition to the buil cs triggered slope instabilities and eventually established fluvial conditions all over the study area with the exception of the anticline crests the relatively high rate of tectonic subsidence in the study area suppressed relative sea level falls resulting in development of discontinuous lowstand strata and bounding surfaces the segmented nature of many regressive unconformities may be related to incremental growth of thrust related structures and each segment is separated from neighbouring segments by gaps of limited vertical and lateral displacement precursors of progressive unconformities are seen in the upper proximal part of the comaron cs by downdip fanning and updip convergence of minor sequences these differentially tilted stratal units provide reliable indicators of syn sedimentary tectonism

shallow marine fan delta slope deposits with large scale cross stratification the plio pleistocene zaimokuzawa formation in the ishikari hills northern japan abstract the plio pleistocene zaimokuzawa formation comprises marine to fluvial deposits in one of the neogene back arc basin around the japanese islands five sedimentary facies facies a e and two facies associations fa 1 and fa 2 were distinguished in the lower zaimokuzawa formation facies a is cross stratified sandstone induced by tidal currents facies b is a couplet of wave rippled fine sandstone and siltstone facies c is pebbly sandstone interpreted as the deposit from a concentrated density flow and a turbidity flow facies d is pebbly mudstone deposited from a mud flow or debris flow facies e is a slumped alternation of sandstone and mudstone fa 1 and fa 2 are typical of the lower and upper parts of the lower zaimokuzawa formation respectively fa 1 is composed of alternations of facies a and c including facies b d and e facies c and d have lobe like geometries in fa 1 fa 2 is composed of facies b and c and lacks facies a facies b and c fill concave upward slump scars in fa 2 the constituent facies shapes of the deposits and paleocurrent directions suggest that the lower zaimokuzawa formation was formed by progradation of a shallow marine fan delta slope influenced by tidal currents and that its lower fa 1 and upper part fa 2 corresponds to middle lower and upper slope deposits respectively wave and tidal currents reworked and redeposited the sediments supplied by gravity driven processes on the delta slope to form the multiple facies associations grain sizes of facies a and b which are mainly composed of sand sized particles in spite of the presence of intervening pebbly deposits of sediment density flows imply competence of the reworking processes the distribution of cross stratified sandstone is restricted to the western area indicating a local inequality in the influence of tidal currents

inter source body wave propagations derived from seismic interferometry summary seismicinterferometrycombinedwithsource receiverreciprocityhasrecentlybeenemployed to extract inter source wave propagations in this study we applied the technique to seismograms of earthquakes that occurred at depths of 300 500 km beneath the bonin islands the wavelets of direct p and s waves generated by the deep earthquakes were examined to compute cross correlation functions ccfs we stacked the ccfs observed at receivers around the stationary point whose location could be estimated by the ray tracing technique because the phases in such ccfs potentially emerge at similar lag times that is the stationary phases the results demonstrate the retrieval of direct p and s waves propagating between pairs of deep earthquakes in particular direct p waves are reconstructed for most event pairs the following points should be considered to effectively retrieve the propagation of body waves 1 it is important to design a geometry in which the stationary phase derived from two earthquakes can be observed at the employed stations 2 the lag time difference of the stationary phases that emerge in the employed ccfs should be as small as possible and 3 the direct waves associated with deep earthquakes have a large amplitude at stations employed for cross correlation which is accomplished by both low noise level at the stations and the radiation pattern of the sources

facies in a shelf edge delta an example from the subsurface of the gulf of mexico middle pliocene mississippi canyon block 109 two vertically stacked shelf edge delta systems in the middle pliocene of mississippi canyon block 109 have been described using a three dimensional seismic survey 400 ft 122 m of conventional core and electric logs possible characteristic facies associations and features of these shelf edge deltas include extensive upper delta slope deformation locally ponded slump induced turbidites in the upper slope a complex association of gravity and tractional deposits relatively thin preserved mouth bar deposits and the absence of delta plain facies six facies have been identified in cores 1 structureless sands interpreted as high density turbidites 2 laminated sands 2 1 sharp based planar horizontal laminations interpreted as bouma b and bc division turbid tes 2 2 low angle discordant laminations interpreted as strong wave activity deposits 2 3 a complex mixture of lamination styles that may be a product of turbidity currents waves or possibly river fed underflows 3 thinly interbedded ripple laminated sands including 3 1 asymmetrical cross laminations interpreted as unidirectional traction current lamination and 3 2 c division turbidites or ripple lamination with mud drapes on foresets or with a symmetrical form interpreted as wave or possibly tidal current lamination 4 contorted muddy fine sands and silts interpreted as mud flows and slumps 5 laminated silts and muds interpreted as low energy wave deposits or possibly d division turbidites and 6 muds interpreted as quiet water deposits in the cored intervals o the deltas turbidite sands immediately overlie muddy slumps in the upper delta slope suggesting that retrogressive slope failure of developing slump structures tapped back into the mouth bar causing sandy turbidity currents to develop the upper delta is represented on seismic data as a series of prograding clinoforms approximately 400 ft 122 m thick electric logs indicate these clinoforms are composed of a lower mud dominated interval an upper delta slope dominated by slumps with areally restricted turbidite sands and coarsening and cleaning upward mouth bar deposits composed of ripple laminated and parallel laminated sands interbedded with muds and silts the lower delta contains similar vertical sequences but also contains a distinct log and seismic facies that may be either a major shelf edge failure or a later channel feature incised across the entire delta apart from this possible channel neither delta shows evidence of emergent delta plain facies

the first second of volcanic eruptions from the erebus volcano lava lake antarctica energies pressures seismology and infrasound 1 we describe a multiparameter experiment at erebus volcano antarctica employing doppler radar video acoustic and seismic observations to estimate the detailed energy budget of large up to 40 m diameter bubble bursts from a persistent phonolite lava lake these explosions are readily studied from the crater rim at ranges of less than 500 m and present an ideal opportunity to constrain the dynamics and mechanism of magmatic bubble bursts that can drive strombolian and hawaiian eruptions we estimate the energy budget of the first second of a typical erebus explosion as a function of time and energy type we constrain gas pressures and forces using an analytic model for the expansion of a gas bubble above a conduit that incorporates conduit geometry and magma and gas parameters the model consistent with video and radar observations invokes a spherical bulging surface with a base diameter equal to that of the lava lake the model has no ad hoc free parameters and geometrical calculations predict zenith height velocity and acceleration during shell expansion during explosions the energy contained in hot overpressured gas bubbles is freed and partitioned into other energy types where by far the greatest nonthermal energy component is the kinetic and gravitational potential energy of the accelerated magma shell 10 9 j seismic source energy created by explosions is estimated from radar measurements and is consistent with source energy determined from seismic observations for the generation of the infrasonic signal a dual mechanism incorporating a terminally disrupted slug is proposed which clarifies previous models and provides good fits to observed infrasonic pressures a new and straightforward method is presented for determining gas volumes from slug explosions at volcanoes from remote infrasound recordings

synsedimentary faulting in a mesozoic deltaic sequence svalbard arctic norway fault geometries faulting mechanisms and sealing properties distributary channel sandstones of the lower cretaceous helvetiafjellet formation and underlying prodelta shales and thin bedded sandstones of the upper jurassic janusfjellet formation exposed along the east coast of spitsbergen are cut by syndepositional planar and listric faults forming collapse scars with depths of 35 90 m and widths up to 1 5 km the fault zones mostly have a dip of 40 60 a width of up to 2 3 m and contain fault parallel 3 5 m long overlapping sandstone sheets with widths of 5 40 cm and up to 2 m thick fault parallel sandy mudstones the intrafault sandstones show fault parallel banding resulting from differences in detrital clay content and grain size the banding has been enhanced by selective late diagenetic quartz cementation of the clay poor bands thin clay laminae now developed into fault parallel stylolites occur along the margins of the intrafault sandstones the clay laminae do not emerge from clay layers in the fault blocks and are not clay smears the laminae probably formed during faulting when fluidization within the fault zones allowed clay particles to move laterally and accumulate along the margins of the fault zones there is no enhanced cementation or cataclastic deformation within the fault zones the ability of the fault zones to act as capillary seals or barriers to fluid flow is therefore mostly determined by the clay laminae rimming the intrafault sandstones

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

late quaternary slumps and debris flows on the scotian slope the scotian slope just west of verrill canyon was surveyed using the sea marc i deep towed sidescan sonar system high resolution seismic reflection profiles and 25 piston cores the generally smooth continental slope has a gradient of 2 5 it is crossed by 2 small valleys that are 1 km wide and 100 m deep much of the sea bed shows evidence of surficial sliding that removed 10 20 m of sediment and the slide scars give the sea bed a steplike morphology from the 600 m isobath to 1 800 m there extend 2 zones of disturbed sediment these disturbed zones have the rough surface and transparent acoustic character previously regarded as characteristic of debris flows but sidescan sonar images and cores suggest that they are principally rotational slide deposits with true debris flows at their distal limits streamlined erosional depressions near the downslope edge of the debris flows cut both the flow and sediment farther down slope these may have been produced by a turbidity current associated with the debris flows sorted coarse sand in piston cores provides further evidence of current activity this widespread sediment failure on relatively low slopes was probably the result of a large earthquake that can be dated from cores as occurring between 5000 and 12000 yr b p

time lapse monitoring of seismic velocity associated with 2011 shinmoe dake eruption using seismic interferometry an extended kalman filter approach seismic interferometry is a powerful tool to monitor the seismic velocity change associated with volcanic eruptions for the monitoring changes in seismic velocity with environmental origins such

sedimentology and kinematics of a large retrogressive growth fault system in upper carboniferous deltaic sediments western ireland growth faulting is a common feature of many deltaic environments and is vital in determining local sediment dispersal and accumulation and hence in controlling the resultant sedimentary facies distribution and architecture growth faults occur on a range of scales from a few centimetres to hundreds of metres with the largest growth faults frequently being under represented in outcrops that are often smaller than the scale of feature under investigation this paper presents data from the exceptionally large outcrops of the cliffs of moher western ireland where a growth fault complex affects strata up to 60 m in thickness and extends laterally for 3 km study of this namurian upper carboniferous growth fault system enables the relationship between growth faulting and sedimentation to be detailed and permits reconstruction of the kinematic history of faulting growth faulting was initiated with the onset of sandstone deposition on a succession of silty mudstones that overlie a thin marine shale the decollement horizon developed at the top of the marine shale contact for the first nine faults by which time aggradation in the hangingwall exceeded 60 m in thickness after this time failure planes developed at higher stratigraphic levels and were associated with smaller scale faults the fault complex shows a dominantly landward retrogressive movement in which only one fault was largely active at any one time there is no evidence of compressional features at the base of the growth faults thus suggesting open ended slides and the faults display both disintegrative and non disintegrative structure thin bedded distal mouth bar facies dominate the hangingwall stratigraphy and in the final stages of growth fault movement erosion of the crests of rollover structures resulted in the highest strata being restricted to the proximity of the fault these upper erosion surfaces on the fault scarp developed erosive chutes that were cut parallel to flow and are downlapped by the distal hangingwall strata of younger growth faults

facies architecture and stratigraphic evolution of a river dominated delta front turonian ferron sandstone utah u s a abstract facies architectural analysis of a river dominated deltaic parasequence in the turonian ferron sandstone member near factory butte utah was conducted to determine the hierarchical spatial arrangement of mouth bars and their role in constructing the delta five architectural elements were identified using 21 measured sections paleocurrent measurements and bedding diagrams they are 1 prodelta pf 2 frontal splay fs 3 detached distal bars dbs 4 distributary mouth bars dmbs and 5 terminal distributary channels tdcs lower in the parasequence detached bars consist of proximally located cross bedded and quasi parallel laminated subaqueous bars that onlap the delta front slope and grade distally into finer grained distal delta front splays these bars translate downstream in a progradational aggradational degradational trajectory and are overlapped by adjacent bars forming a bar assemblage these bars are interpreted to have been deposited by descending hyperpycnal flows as a decelerating axial jet deposition of these bars occurs at the delta front to prodelta chokepoint presumably due to flow deceleration the distal bar assemblage is capped by an extensive but discontinuous shale drape suggesting local abandonment upper facies assemblages show a distinct switch to predominantly cross bedded distributary mouth bars corresponding to a decrease in water depth an increase in friction and a likely transition into planar versus axial jets this is indicated by aggrading cross bedded distributary mouth bars that overlie the distal bars laterally the mouth bar deposits are interstratified with terminal distributary channel deposits with prominent scour surfaces at the base separate distributary channels and their bars coalesce ultimately to build the entire delta lobe the detached distal bars prograde locally west to northwest and lack fair weather wave formed sedimentary structures suggesting a local embayment along the regionally northeast prograding shoreline low levels of ichnofaunal diversity indicate a stressed river dominated setting at the base of the section frontal splays and detached bars dominated by storm driven river flood deposits are deposited over muddy prodelta facies detached bars are likely initiated about 500 meters distal of the distributary channel in water depths of 10 30 meters based on the thickness of the parasequence once this subaqueous platform is constructed by the distal bar assemblage more proximal distributary mouth bars fill the remaining shallow water accommodation as the system continues to shallow distributary channels override and scour the bars reflecting reduced accommodation

eocene seismicity in the pyrenees from megaturbidites of the south pyrenean basin spain abstract the triggering mechanism for emplacement of nine calcareous megaturbidites mt in the clastic turbidite eocene basin of the pyrenees is examined the thickness of each mt is 10 to 200 m and their volume may reach 200 km 3 their mobilization is thought to result from seismic activity related to thrust faults along the northern border of the basin we attempt to define the seismic characteristics for a volume of 100 km 3 the dimensions of the slope failures are estimated to be 100 5 10 0 1 0 2 km and related to a fault rupture length of about 50 100 km and liquefaction of basal clayey layers given these two constraints superficial earthquakes of m 7 would be required to initiate landslides

formation of the yakuno ophiolite accretionary subduction under medium pressure type metamorphic conditions abstract the notion that the yakuno ophiolite and overlying maizuru group represents an accretionary prism formed during the permian evolution of japan on the yakuno eruptive sequence association of hemipelagic mudstone with silicic tuff exotic fossiliferous limestones derived from previously accreted sea mounts upward coarsening of sequences terrigenous sandstone and conglomerate and mildly deformed permian and triassic forearc basin formations the most important indicator however is the seaward imbrication and repetition observed in both the maizuru group and the ophiolite itself d1 deformation structures include axial planar foliations pressure solution cleavage for the maizuru group and granulite amphibolite metamorphic layering in the ophiolite flattening type strain symmetric pressure shadows and fringes and isoclinal folds showing axial planar foliations and thrust faulting at their overturned limb the exceptional asymmetry observed indicates seaward directed shearing near the thrust while d1 structures in the maizuru zone are explained by off scraping above the basal decollement the later jurassic d2 kink fold structure includes a first order asymmetric kink with a brittle thrust at its overturned limb more or less coeval with m2 retrograde metamorphism medium pressure m1 prograde metamorphism in the yakuno ophiolite produced layering of granulite and amphibolite and in the maizuru group formation of illite along pressure solution cleavage of mudstones the metamorphic grade is controlled by the stratigraphic relationships and appears typical of that in ocean floor regions however there was only one episode of m1 prograde metamorphism which occurred contemporaneously with d1 off scraping given that subduction zones are normally characterized by high p t metamorphic regimes the observed p t history appears to reflect relatively unusual conditions such high thermal gradients may plausibly reflect the approach of a young hot oceanic plate which continued subducting beneath the japanese arc accordingly the yakuno ophiolite was probably formed at the trench trench ridge triple junction

the theropod that wasn t an ornithopod tracksite from the helvetiafjellet formation lower cretaceous of boltodden svalbard

empirical synthesis of time asymmetrical green functions from the correlation of coda waves we demonstrate the existence of long range field correlations in the seismic coda of regional records in alaska the cross correlations between the different components of coda records at two points are measured for a set of distant earthquakes remarkably while individual correlations have a random character the correlations averaged over source and time exhibit deterministic arrivals that obey the same symmetry rules as the green tensor between the two points in addition the arrival times of these waves coincide with propagating surface waves between the two stations thus we propose to identify the averaged correlation signals with the surface wave part of the green tensor we observe the causal and anticausal parts of the green function however we find experimentally that amplitudes at positive and negative times are not equal we explain this observation by the long lasting anisotropy of the diffuse field we show that the flux of energy coming from the source can still dominate the late coda and result in nonsymmetric cross correlations when the distribution of earthquakes is not isotropic around the stations the extraction of green functions from coda waves allows new types of measurements with seismic waves along paths between stations that could not be obtained with the waves produced by earthquakes

small and large scale soft sediment deformations in a triassic lacustrine delta caused by overloading and seismicity in the ordos basin central china abstract the instability of an upper triassic lacustrine deltaic system in the southwestern ordos basin central china is examined based mainly on detailed measurements and descriptions of core data nine lithofacies associations are identified including undeformed and deformed channel deposits sandy and muddy slumps sandy debrites sandy dykes undeformed and deformed fringe silty deposits and muddy deposits quantification of the vertical and horizontal spatial distribution of these sediments reveals the deformed sediments can comprise more than one third of the entire cored interval in more than half of the wells indicating the significance of soft sediment deformation structures as essential components of this deltaic system a depositional model is constructed which highlights the location of deformed and remobilized sediments and their relationships with undeformed sediments in the proximal part of the delta the undeformed and deformed channel deposits and sandy slumps dominate the sandy sediments which are interbedded to form thick amalgamated sandstones in areas distant from these massive sandstones undeformed and deformed fringe fine grained deposits are well developed which could generate muddy slumps in the distal part of the delta besides undeformed and deformed fringe fine grained deposits sandy debrites are present as isolated sandbodies large scale sandy dykes formed between thick sandstones and adjacent mudstones two possible trigger mechanisms for initial deformation development are identified sediment overloading induced by sudden deposition of remobilized sediments and seismicity which caused large scale remobilization in the study area the high percentage of soft sediment deformation structures in this delta influences the reservoir heterogeneity of the three types of sandstones undeformed channel deposits sandy slumps and sandy debrites porosity permeability analysis reveals that reservoir quality of these three types varies significantly and thus distinguishing deformed sediments from undeformed deltaic sediments is essential for hydrocarbon development in this area

shallow water gravity flow deposits chapel island formation southeast newfoundland canada a remarkable suite of shallow water gravity flow deposits are found within very thinly bedded siltstones and storm generated sandstones of member 2 of the chapel island formation in southeast newfoundland medium to thick siltstone beds termed unifites range from non graded and structureless type 1 to slightly graded with poorly developed lamination type 2 to well graded with lamination similar to that described for fine grained turbidites type 3 unifite beds record deposition from a continuum of flow types from liquefied flows type 1 to turbidity currents type 3 calculations of time for pore fluid pressure dissipation support the feasibility of such transitions raft bearing beds consist of siltstone with large blocks or rafts of thinly bedded strata derived from the underlying and adjacent substrate characteristics suggest deposition from debris flows of variable strength estimates of debris strength and depositional slope are calculated for a pebbly mudstone bed using measurable and assumed parameters an assumed density of 2 0 g cm 1 and a compaction estimate of 50 gives a strength estimate of 79 7 dyn cm 2 and a depositional slope estimate of 0 77 the lithologies and sedimentary structures in member 2 indicate an overall grain size distribution susceptible to liquefaction inferred high sediment accumulation rates created underconsolidated sediments metastable packing types of sediment failure included in situ liquefaction disturbed bedding sliding and slumping raft bearing debrites resulted from sliding and incorporation of water locally hummocky cross stratified sandstone directly overlies slide deposits and raft bearing beds linking sediment failure to the cyclical wave loading associated with large storms the gravity flows of the chapel island formation closely resemble those described from the surfaces of modern mud rich marine deltas details of deltaic gravity flow deposition from this and other outcrop studies further our understanding of modern deposits by adding a third dimension to studies primarily carried out with side scan sonar

deep sea fan deposits in the macigno formation middle upper oligocene of the gordana valley northern apennines italy abstract facies characteristics are described for a 2300 m thick turbidite succession of the macigno formation middle upper oligocene which crops out as a continuously exposed section in the gordana valley northern apennines in the study area the macigno formation consists of two sandy members separated by a shaly member the sandy members contain lithic associations characteristic of submarine fan deposits and form distinct fan complexes the middle shaly member represents a period of basin starvation three main facies associations are recognized in the macigno fan deposits fan fringe outer fan lobe and braided midfan facies associations the fan fringe deposits consist of monotonous or small scale cyclically arranged thin bedded turbidites the outer fan lobe deposits are composed of medium to very thick bedded classical turbidites internally organized in thickening upward cycles with minor intercalations of thin bedded sandstone beds two distinct types of outer fan lobe deposits distal and proximal are recognized on the basis of rock type internal organization and vertical facies relationships the midfan deposits consist of amalgamated massive sandstone and pebbly sandstone which display repeated thinning upward cycles the three main facies associations are superposed t define major thickening and coarsening upward cycles reflecting distinct episodes of fan progradation the relationships between the facies associations of the macigno deposits and the existing models of submarine fan sedimentation are discussed after the deposition of the fan complexes fan sedimentation in this part of the basin was replaced by movements of allochthonous units heralded by large olistostromes

fault zone imaging from correlations of aftershock waveforms we image an active fault zone environment using cross correlations of 154 15 s long 1992 landers earthquake aftershock seismograms recorded along a line array a group velocity and phase velocity dispersion analysis of the reconstructed rayleigh waves and love waves yields shear wave velocity images of the top 100 m along the 800 m long array that consists of 22 three component stations estimates of the position width and seismic velocity of a low velocity zone are in good agreement with the findings of previous fault zone trapped waves studies our preferred solution indicates the zone is offset from the surface break to the east 100 200 m wide and characterized by a 30 velocity reduction imaging in the 2 6 hz range resolves further a high velocity body of similar width to the west of the fault break symmetry and shape of zero lag correlation fields or focal spots indicate a frequency and position dependent wavefield composition at frequencies greater than 4 hz surface wave propagation dominates whereas at lower frequencies the correlation field also exhibits signatures of body waves that likely interact with the high velocity zone the polarization and late arrival times of coherent wavefronts observed above the low velocity zone indicate reflections associated with velocity contrasts in the fault zone environment our study highlights the utility of the high frequency correlation wavefield obtained from records of local and regional seismicity the approach does not depend on knowledge of earthquake source parameters which suggests the method can return images quickly during aftershock campaigns to guide network updates for optimal coverage of interesting geological features

deltaic systems and their contribution to an understanding of basin fill successions s u m m a ry deltaic systems are prominent features of many clastic basin fill successions throughout the geological record and are also important as sites of fossil fuel reserves the process based classification of deltaic systems into fluvial wave and tide dominated types adopted in recent years remains valid but requires additional information on for example the sediment load of the system its position in the basin and the extent of synsedimentary deformation in order to be a meaningful characterization of a delta the range of delta types is further extended by research into ancient deltaic systems which can result in the definition of a non actualistic delta which differs from modern systems this is an important trend which should develop in the future as well constrained ancient systems are characterized to their full extent a further avenue of future research lies in examining the nature of links of deltaic systems to shelf slope and submarine fan systems with particular reference to depositional analysis of seismic stratigraphic information deltaic systems are important elements of many clastic basin fill successions they are important in their own right and have significant links with alluvial shelf slope and deep sea fan systems interpretations of sediment dispersal and deposition in clastic basins are often greatly enhanced if the position character and behaviour of basinmargin delta systems are constrained deltaic successions are also important economically organic rich shales and coals can be important as hydrocarbon source rocks sandstone bodies serve as reservoirs in numerous hydrocarbon provinces and significant coal reserves are hosted in deltaic successions modern and ancient deltaic systems have been extensively researched for many decades with many of the basic principles of sedimentation such as cyclicity facies and sequence analysis being developed and tested in these successions however despite the longevity and high quality of this research important problems still remain the aim of this paper is to review recent progress in deltaic studies and to identify outstanding problems which are currently attracting attention or might do so in the near future the paper commences by considering various aspects of deltas as discrete depositional systems and continues by discussing the links between deltas and other depositional systems in clastic basin fill successions

hyperpycnites deposited 700 km away from river mouths in the central japan sea abstract relatively little is known about the characteristics of deposits and potential runout distances of hyperpycnal currents this study describes and discusses evidence of sediment deposition from sustained long duration quasi steady turbidity currents in the distal part of the toyama deep sea channel which extends ca 700 km from river mouths in the central japan sea the study is based on gravity cores and airgun seismic reflection profiles obtained from the channel distal reaches the silty turbidite beds of the channel s terminal fan show rhythmic layering that indicates sustained turbidity currents with distinct flow strength fluctuations some of the rhythmite beds show a fining upward internal trend net flow strength waning whereas others show an upward coarsening net flow strength waxing followed by fining seismic reflection profiles from the channel levees show large bedforms of climbing dune type attributed to the spillover of thick sustained turbidity currents the deposition of the terminal fan rhythmites and accretionary levee bedforms is attributed to turbidity currents generated by hyperpycnal river effluent a quantitative assessment of sediment concentrations in the coastal rivers indicates that their effluents could become hyperpycnal nearly every year or during every major seasonal flood the density of a river generated underflow would increase by the entrainment of saline water and seafloor sediment on the steep slope of the toyama bay resulting in robust long runout turbidity currents the estimated flow velocities of these currents were around 0 3 m s and their recurrence period for the last 1000 years was of the order of 70 years the estimated duration of hyperpycnal flows required for the deposition of rhythmite beds 700 km away from the river mouth is of the order of several days to 3 4 weeks the study provides new insights into the recognition and classification of hyperpycnites in distal zones of deep marine turbiditic systems

reflection images from ambient seismic noise one application of seismic interferometry is to retrieve the impulse response green s function from crosscorrelation of ambient seismic noise various researchers show results for retrieving the surface wave part of the green s function however reflection retrieval has proven more challenging we crosscorrelate ambient seismic noise recorded along eight parallel lines in the sirte basin east of ajdabeya libya to obtain shot gathers that contain reflections we take advantage of geophone groups to suppress part of the undesired surface wave noise and apply frequency wavenumber filtering before crosscorrelation to suppress surface waves further after comparing the retrieved results with data from an active seismic exploration survey along the same lines we use the retrieved reflection data to obtain a migrated reflection image of the subsurface

large scale submarine rotational slumps and growth faults in the eastern mediterranean submarine slumps with areas of 1000 km2 and more disturb the continental margin of israel and nearby areas in them the plio quaternary silty clayey sediments up to 1 5 2 km thick are broken by shore parallel growth faults into 5 10 blocks which are generally rotated and tilted landward the faults flatten downward and become rooted in ridges formed by deformation of the underlying mobile messinian evaporite bearing series deformation is thin skinned and does not visibly extend to deeper levels slumping occurred only where a sufficiently thick overburden accumulated over a sufficiently well developed mobile substrate then gravitational instability developed and led to basinward sliding of the continental margin sediments over the messinian series which acted as a lubricant and a level of decollement the mobility of this series is probably caused by overpressured shale beds that are confined between the impervious evaporites this mechanism explains all the features of the slumps hitherto faults directly related to the slumps of the eastern mediterranean were not identified but since the region is tectonically active it is not possible to exclude the possibility that basinward sliding was triggered either by motion of minor underlying faults or by seismic shaking however it seems that even if this were the case slumping could be triggered only because the continental margin was anyhow gravitationally unstable or close to such a state therefore the gravitational instability was the main factor that controlled the deformation of the pliocene quaternary sediments the slumps of the eastern mediterranean resemble large scale slumps that are known from other passive continental margins in the world

nearshore mesozoic basins off nordland norway structure age and sedimentary environment abstract seismic data acquisition along the nordland coast norway has resulted in the discovery of two downfaulted sedimentary basins of mesozoic age in an area of precambrian lower palaeozoic metamorphic rocks the stabbfjorden basin informal name west of meloya has a sedimentary rock succession that is up to 800 m thick while the lyngvaerfjorden basin informal name northeast of traena is at least 350 m deep microfossil dating of ice transported erratic blocks thought to be eroded from these basins and found on nearby skerries range in age from barremian to triassic the majority of the samples are of middle late jurassic age the sedimentary blocks comprise conglomerates sandstones siltstones and mudstones and frequently contain shells and coal fragments lithofacies analyses show that they reflect shallow marine deposition but it is possible that the oldest samples were deposited in a continental environment the lithofacies reflect the well known tectonic phases and sea level changes that have been reported for the middle jurassic early cretaceous in the nordland offshore region vitrinite reflectance measurements show that organic material in the samples can be classified as immature and the newly discovered basins have no hydrocarbon exploration potential

high paleogeothermal gradient with ridge subduction beneath the cretaceous shimanto accretionary prism southwest japan paleotemperature in the jurassic chichibu and the cretaceous shimanto accretionary complexes southwest japan increases southward generally without regard to the early phase geologic structure there is an exceptional peak in the okitsu melange and the thermal structure probably formed after accretion of the complex the estimated geothermal gradient is more than 90 c km in the okitsu melange and more than 50 c km elsewhere in the complex the ophiolitic okitsu melange formed concurrently with eocene subduction of the kula pacific ridge under the cretaceous accretionary prism the previous thermal structure was overprinted by this event

reconstructing green s function by correlation of the coda of the correlation c3 of ambient seismic noise analysis of long range correlation of the microseisms has been shown to provide reliable measurements of surface wave speeds that can be used for seismic imaging and monitoring in the case of an even distribution of noise sources it has been theoretically demonstrated that the correlation is the exact green s function including all types of waves this method is limited in its application by the actual source distribution in practice the azimuthal distribution of energy flux of the noise is dominated by some particular directions resulting in a clear azimuthal dependence of the quality of the reconstruction of rayleigh waves with a poor reconstruction in some azimuths to solve this problem we use noise correlations measured on the entire network we consider two stations a and b for which the rayleigh waves could not be discerned in the in the correlation of continuous records of ambient noise we computed all correlations between the station a respectively b and all the 150 other stations located at regional distances theoretically these virtual seismograms contain direct waves and coda although they are clearly contaminated by the influence of the imperfect ambient noise field and most are inadequate for direct analysis we used these correlation functions as equivalents to seismograms produced by sources acting at the 150 stations locations and recorded in a respectively b we select time windows in those virtual seismograms that correspond to coda and compute correlations between them this metacorrelation is found to exhibit the surface wave part of the green s function that was not visible in the raw correlation of ambient noise we illustrate the legitimacy of the reconstruction by comparison with raw noise correlations this procedure can be used to assess seismic velocity between stations even in presence of a directive and poorly oriented ambient noise the result shows that in spite of the small signal to noise ratios often seen in correlations of ambient noise especially at large lag time corresponding to coda their codas are better equipartitioned than was the ambient noise upon which they were based they are therefore presumably multiply scattered and contain information on both direct surface waves and also on more complex travel paths

palaeomagnetic characteristics of drill cores from middle jurassic delta plain sediments the brent group north sea abstract low level palaeomagnetic signals in hydrocarbon producing delta plain reservoir sediments from the ness formation of the middle jurassic brent group west of the gullfaks sor field are the result of low concentrations of magnetic constituents analysis of magnetic extracts suggests the presence of single to pseudo single domain magnetite in addition to pyrrhotite scanning electron microscopy confirms the presence of detritus derived magnetite minor quantities of haematite goethite and spherical magnetite possibly of diagenetic origin acid dissolution experiments suggest that reactive iron is responsible for 90 of the magnetic susceptibility the stable remanent magnetization in a 75 m core section is carried by detrital magnetite which is probably of post depositional origin the presumably diagenetic pyrrhotite carries a predominant chemical remanent magnetization which it is suggested was acquired more or less contemporaneously with the detrital magnetization

a model for cutting and healing of deltaic mouth bars at the shelf edge mechanism for basin margin accretion abstract the architecture and facies variability of shelf edge deltaic deposits from permian triassic strata of the karoo basin south africa are described the architecture of the deposits are used to propose a model of repetitive collapse and re establishment of mouth bar packages at the shelf edge and associated delivery of sand to the slope and basin floor accretion of basin margin sediment wedges is facilitated through deposition of sediment on the basin margin clinoform this sediment is delivered by deltas at the shelf edge in the form of turbidity currents delta collapse and other gravity driven processes a well exposed 3 km long transect that records the transition between the outer shelf and upper slope for one progradational unit is described the strata are defined by basinward dipping offlapping clinoform packages of soft sediment deformed and undeformed sandstone and mudstone undeformed sandstone units are characterized by meter thick beds of mouth bar sandstones with internal scour incisions 1 2 m deep sets of undeformed sandstone beds thicken in a basinward direction from less than 1 m to over 10 m and in multiple locations the bed sets are truncated by slump scar surfaces that are overlain by mass transport deposits soft sediment deformed strata are defined by packages of contorted broken and overturned beds the deformed deposits are interpreted as being the product of dewatering features as well as slumps slides and debrites all of which emanate from slump scar features at the shelf edge on the uppermost slope thin bedded prodelta turbidites are interbedded with mass transport deposits most of which pinch out within 2 km of the shelf edge the clinoformal packages presented record the basinward transition between a prograding mouth bar deposits on the delta topset b truncation of the mouth bar deposits by slump scar incisions 2 6 m deep c deposition of mass transport deposits on the delta front and prodelta and finally d re establishment of mouth bar deposition above and basinward of the slump scar and mass transport deposits the observed stratigraphic stacking patterns facies transitions and interpreted depositional systems form the basis of a model for cutting and healing of deltaic packages that describes the repetitive deltaic progradation delta collapse and subsequent re establishment of deltaic deposition this process of repetitive collapse and reestablishment records the depositional element scale progradation of the shelf edge and accretion of the basin margin within the same depositional sequence

facies analysis and its relation to point sourced growth faults in river dominated prodeltaic delta front deposits of the cretaceous ferron notom delta utah usa abstract this study evaluates the evolution of a small scale growth fault within a deltaic parasequence of the ferron sandstone utah analysis is based on 4 stratigraphic logs and a panorama covering 100 m of lateral exposure five growth fault blocks are displayed in strike and dip views the listric faults dip basinward and sole out into bedding parallel decollement surfaces associated with deformed prodelta shales which also form diapirs throw on individual faults averages 4 m and heave increases with depth from 2 5 to 5 m strikes on fault planes average 160 and fault dip decreases with depth from 50 to 0 where they become parallel to bedding pre growth facies comprise heterolithics with abundant graded beds current ripples wave ripples small scale soft sediment deformation and a low bioturbation index this indicates deposition in a river dominated storm influenced delta that was supplied primarily by storm triggered flood events and prograded rapidly growth strata are primarily planar and quasi planar fine sandstones deposited as upstream and downstream accreting mouth bars faulting initiates with the building of a critical load reflecting a low angle delta front foreset probably linked to deposition in a mouth bar mobile prodelta muds form diapirs that breached the sediment water interface providing accommodation for the fault blocks termination of faulting occurred when sandy growth strata contacted and locked into higher strength pre growth heterolithics deeper in the section minor deformation of growth strata is demonstrated by synthetic microfaulting in growth sands this study emphasizes a localized stress field i e point sourced associated with sandy mouth bar deposits which acted as fault initiation points this contrasts with the distributed stress regimes commonly associated with regional scale growth faults along continental margins this can lead to expanded but localized reservoir compartments within river dominated deltaic systems especially those in epeiric seas or other shallow water sedimentary basins such as prudhoe bay field alaska

mechanisms of collapse of the cretaceous helvetiafjellet formation at kvalvagen eastern spitsbergen coastal cliffs at kvalvagen eastern spitsbergen expose palaeolandslide blocks and related slope failure features that record local collapse of an otherwise undisturbed succession of paralic sediments the collapse occurred along a shallow sloping shelf at the edge of an epicontinental sea in the early cretaceous the event was coincident with a rise in relative sea level along a coast that had just previously experienced a major paralic regression across a muddy marine environment the low relief environment in which the slope failure structures formed as well as the timing of the collapse raise questions regarding the cause of the topographic instability and the possible influence of sea level changes or tectonic activity these outcrops have been previously interpreted as the collapse of a deltaic system triggered by local seismic activity or collapse of a shelf break in the headwall regions of submarine canyons this paper presents new structural and stratigraphic data that refine and adjust the previous interpretations through the evaluation of a variety of possible mechanisms for collapse based on the new data our data suggest that active delta deposition was not occurring at kvalvagen at the time of collapse and that the collapse was likely due to allogenic forcing despite the possible influence of pore fluids and rheological controls on the collapse we find that the geometry and kinematics of landslide slip planes synsedimentary folds and other slope failure related features require over steepened topography and that these are most consistent with westward directed collapse off of a north striking escarpment with elevated topography on the east side fault exposures a large contrast in palaeo elevation and liquifaction features support previous interpretations of a tectonic cause for the collapse and suggest that this topographic feature may have been a fault or fold scarp this study demonstrates the importance of combining stratigraphic and sedimentological data with structural data and kinematic analysis in the interpretation of sedimentary processes

geology of the campanian m1 sandstone oil reservoir of eastern ecuador a delta system sourced from the amazon craton abstract the campanian m1 sandstone member of the napo formation is one of the main reservoirs of the capiron tiputini oil play system of the eastern part of the oriente basin of ecuador this study presents a geological model for this reservoir at the apaika and nenke oil fields included within the block 31 and the eden yuturi oil field operated by petroamazonas ep the geological characterization of the m1 sandstone is based on an integrated study which includes core description electric log analyses and seismic data interpretation the sedimentological descriptions from available cored sections show that m1 sandstone records a variety of fluvial to shallow marine processes including mass flow and delta front turbidity currents not previously documented the stratal stacking pattern interpreted from electric logs indicates that the succession reflects deltaic progradation rather than the backstepping pattern typically displayed by the underlying albian to santonian sediments of the napo formation seismic rms amplitude defines clinoform geometries with sigmoidal sand body architecture prograding from east to west correlation with neighboring regions in colombia suggest that the m1 sandstone was probably part of a large river dominated delta system sourced from the east during major campanian progradation the location of the source area of sediment was determined using u pb detrital zircon dating provenance ages are uniform within the m1 sandstone cluster in a population that ranges from 1 4 to 1 6 billion years these ages indicate that sands were derived mostly from erosion of the lithotectonic rio negro jurena province located to the northeast of the studied area detrital ages from the overlying maastrichtian tena formation include ages between 80 and 200 ma pointing to an important change in the source areas located in the eastern cordillera of ecuador the change in sediment supply from east to west recorded in the tena formation coincide with the initial episodes of the andean orogeny and may be driven by the collision of fragments of the caribbean large igneous province clip against the continental margin of northwestern south america

initiation of turbidity currents outcrop evidence for eocene hyperpycnal flow turbidites abstract the most widely used although not as widely documented explanation for initiation of turbidites is the conversion of catastrophic sediment failures into turbidites such instantaneous sediment failures generate short lived surge type flows that deposit turbidite beds described as bouma sequences in this communication we present data from the eocene central basin of spitsbergen that shows turbidite systems that are volumetrically dominated by thick ungraded and laminated sandy turbidite beds deposited by gradual aggradation from sustained flows sustained flows are long lived and more or less continuous they can be generated by a variety of mechanisms e g 1 instability during volcanic eruptions and the consequent remobilisation of unconsolidated material 2 seismically triggered subaerial sliding within the drainage 3 storm surges 4 retrogressive slope failure 5 breaching and 6 hyperpycnal flows our database shows that in the eocene central basin the sustained flows were generated by hyperpycnal flows i e by direct river effluent the hyperpycnal flow turbidites have been recognized on the basis of 1 physical connection between fluvial and turbidite channels at the shelf edge 2 abundance of thick turbidite sandstone beds 3 sand prone nature of the turbidite systems 4 downslope changes of individual thick sandy turbidite beds and their collapsed pinch out segments 5 great abundance of continental material leaves coal fragments in turbidite beds 6 low abundance of associated slumped or debris flow beds and 7 the occurrence of turbidites in systematically accreted shelf margins these features strongly suggest that hyperpycnal flow generated by direct river effluent deposited significant number of turbidite beds in the documented slope and basin floor turbidite successions we also argue that the hyperpycnal flows are preferentially fed into the deepwater slopes beyond the shelf edge during the falling stage and lowstand of relative sea level the turbidite beds were studied in the context of seismic scale 1 15 km dip oriented outcrops by measuring detailed vertical sections following individual beds and packages of beds downslope for distances over 5 km lateral mapping and helicopter taken photomosaics

facies relationships recorded in a late paleozoic fluvio deltaic system parana basin brazil insights into the timing and triggers of subaqueous sediment gravity flows abstract this paper aims at documenting the spatial and genetic relationships between fluvial and subaqueous gravity flow deposits in an ancient fluvio deltaic system exposed in the eastern border of the parana basin southern brazil the examined interval comprises the pedra alta sandstone and associated deposits which are included in the glacially influenced late paleozoic itarare group five facies associations were identified and comprise the following coeval depositional settings from the more proximal to the more distal a braided fluvial delta plain b channel mouth zone c delta slope d distal marine glacially influenced and e non cohesive density flow deposits these facies associations form a conformable shallowing upward succession about 200 m thick whose stacking pattern is interpreted as a postglacial progradation the stratigraphic architecture suggests a genetic correlation between high energy fluvial discharges possibly related to meltwater release and coarse grained deposits non cohesive density flow deposits accumulated on the delta foreset and bottomset mass transport deposits were more likely triggered by sediment load increase on the delta slope due to high sediment supply rather than by relative sea level fall the stratigraphic evolution can be reconstructed considering an initial stage characterized by a grounded ice margin and the deposition of mudstones with ice rafted debris glacial stage this stage was succeeded by a second phase in which a fluvial system formed as a result of ice margin retreat farther to the se postglacial stage this glacial postglacial stratigraphic succession is different from that recognized by previous workers in the itarare group a conclusion that impacts greatly in reservoir prediction and modeling in the parana basin

interplay between tectonics and compaction in a rift margin lacustrine delta system miocene of the eger graben czech republic the early miocene bilina palaeodelta consists of fluvio deltaic and lacustrine clastics deposited along the south eastern margin of the extensional most basin part of the eger graben in north bohemia czech republic the bilina succession shows evidence of repeated advances of an axial deltaic system across a thick accumulation of organic material and clay in the hangingwall of an active fault exposures up to ca 4 5 km long in the bilina open cast mine help bridge the gap between seismic scale and typical outcrop scale of observation and thus allow the relationships between small scale and basin scale stratal geometries to be evaluated the bilina palaeodelta deposits include sand dominated fluvial channel fills and heterolithic sheets interpreted as delta plain strata sand dominated mouth bar wedges and heterolithic sheets of prodeltaic deposits passing distally into lacustrine clays the depositional environment is interpreted as a fluvial dominated mixed load lacustrine delta with a high degree of grain size segregation at the feeder channel mouths on the largest temporal and spatial scales variable tectonic subsidence controlled the overall advance and retreat of the delta system the medium term transgressive regressive history was probably driven by episodes of increased subsidence rate however at this temporal scale the architecture of the deltaic sequences deltaic lobes and correlative lacustrine deposits was strongly affected by i compaction of underlying peat and clay which drove lateral offset stacking of medium term sequences and ii growth of a fault propagation fold close to the active bilina fault at the smallest scale the geometries of individual mouth bars and groups of mouth bars short term sequences reflect the interaction among sediment loading compaction and growth faulting that produced high frequency relative lake level fluctuations and created local accommodation at the delta front

growth faults above shale seismic scale outcrop analogues from the makran foreland sw pakistan abstract the southern makran fold thrust belt pakistan displays unique outcrop examples of well exposed kilometre scale listric growth faults that displace miocene age deltaic growth strata by several hundreds of metres to kilometers the largest growth faults are counter regional landward dipping bounding major clastic depocentres exposed over areas 1000 km 2 stratal offset along these faults can exceed 1 5 km fault zone thicknesses range between ca 100 and 400 m and average fault thickness displacement ratios are around 1 10 high resolution satellite data show in unprecedented detail the faults and the stratigraphic architecture of associated growth sequences which comprise kilometre scale progradational clinoforms thick mudstone units and basinwards wedging sandstone shale deposits the true vertical thickness of the syn kinematic record is in places up to 8 km making the outcrop examples equivalent to major growth faulted successions known from seismic data of large deltas and at least an order of magnitude larger than other outcrop examples a comparison of the makran outcrops with seismic reflection examples offshore nw borneo reveals distinct similarities in the gross depocentre geometries and internal architecture the key control for growth faulting is interpreted to result from sedimentary loading with rapid sedimentary progradation causing the development of rollover synclines by differential compaction and fluid expulsion and counter regional growth faults preferentially forming on the basinward side of these synclines the data and interpretations presented can be used to assess the key parameters that contribute to the development of growth faults and growth successions above shale reinforcing structural and stratigraphic observations from seismic interpretation and modelling studies in demonstrating their occurrence in exposure

seismic interferometry of teleseicmic s wave coda for retrieval of body waves an application to the philippine sea slab underneath the japanese islands summary the reconstruction of surface waves from the cross correlation of random wavefields has recently been extensively inspected by theoretical and experimental approaches however the reconstruction of body waves has not been extensively studied in this study we present a method for extracting body waves that is direct p and s waves and reflected waves from the philippine sea slab we use the cross correlation of the wavefield generated by the teleseismic s waves observed by hi net tiltmeters with a passband of 0 07 0 5 hz to enhance the contribution of the s coda we reduced the source time function and the deterministic phases ss scs and ss and the surface wave in s coda the records of the processed s coda observed at every station pair are cross correlated for each teleseismic event the cross correlation functions ccfs of different earthquakes are stacked to retrieve wavefields propagating between the station pairs as a result direct p s and the reflected waves could be extracted when the stacked ccfs are aligned as a function of distance of separation between two stations the gradients of the traveltime curves for the direct p and s waves are approximately 5 7 and 3k m s 1 respectively these velocities correspond to the seismic velocities of the crust or the p wave velocity of the uppermost mantle in order to enhance the reflected waves we searched for the reflection points by assuming that the later phases in the ccfs are ss reflections and map the amplitudes onto the depth sections as a result the negative phases dipping to the north can be traced right below the region of hypocentre distribution these negative phases probably correspond to the oceanic moho within the philippine sea slab we also show that the oceanic moho can also be traced by assuming pp reflections these results indicate that the ccfs plausibly contain information regarding both p and s waves propagating between the two receivers and are capable of detecting reflected phases in addition to the direct waves