modelling seismites with a digital shaking table abstract soft sediment deformation structures induced by seismically triggered liquefaction and or fluidization seismites have been reproduced with a digital shaking table we have used natural sediments with variable granulometric ranges clay silt and sand and an earthquake simulator that is able to reproduce real tridimensional seismograms acceleration and pore pressure recording allowed us to follow liquefaction and or fluidization processes in unconsolidated sediments during earthquakes different types of seismites were produced by variations in the tested sedimentary column

experimental studies of the fluidization of layered sediments and the formation of fluid escape structures experiments demonstrate that fluid escape structures can be produced as a result of unstable fluidization behaviour where a lower base layer of granular material is inhibited from fluidizing by the presence of an overlying non fluidizing top layer before the base layer can fluidize the weight of the overlying material must be balanced and this is accomplished by base layer material pressing against the bottom surface of the confining top layer forming a static layer this static layer allows the top layer to lift away from the base layer which is then free to fluidize a water filled crack forms below the static layer and as this grows instability causes the static layer and top layer to bend and conical voids to form below the antiformal sections rupture occurs at the apex of the water void allowing the underlying water and fluidizing material to burst out through the top layer the fluidized base layer material then flows through the rupture until all of this material except that in the static layer is deposited above the previously overlying layer and a stable fluidization system results the top layer material is bent upwards around the rupture and the resulting pillar type escape structure is preserved if flow then ceases the vigour of the burst out is greatest when the base layer material has a grain size 15 of the top layer material if the base layer grain size is less than 8 of the top layer then base layer material will pass through the top layer pore spaces without forming an escape structure if cohesive material is present escape structures form when a layer of fine grained cohesive material overlies a layer of cohesionless material at low flow rates small pipes with scattered angular bends pierce the top layer and base layer material passes through them the base layer material is ejected on to the top layer and builds up around the mouth of each pipe to form constructional structures sand volcanoes this is in contrast to the cohesionless experiments where the weight of material being deposited on the top layer caused an ejecta filled depression to form around the rupture if flow then ceases both the pipes and the sand volcanoes are preserved at high flow rates where the base layer fluidizes the top cohesive layer becomes fragmented small fragments circulate within the fluidizing base layer and are preserved as floating clasts large fragments sink to the bottom of the fluidizing base layer erosion of the bottom surface of these larger fragments causes this surface to become convex downward the experimentally derived structures are similar to pillar type structures observed in the field and the processes described can be used to investigate the development of these structures fluidization experiments also demonstrate the genesis of dish structures and the cohesive behaviour can be applied to the deformation of these structures after initial formation

observations of near bed velocity profiles and seabed roughness in tidal currents flowing over sandy gravels measurements of near bed velocity profiles and bottom roughness in tidal currents flowing over sandy gravels in the west solent england have shown that although the seabed in the immediate vicinity of the study area was generally level and devoid of regular bed forms the observed velocity profiles were consistently curved concave downwards this behaviour may be attributed to the presence of an internal boundary layer which was due to form drag on irregular topography upstream of the measurement position loosely packed gravels of the type found in the west solent had a geometric mean roughness length of about 0 3 cm comparison of the observed ratio of roughness length to mean particle size with laboratory data suggests an equivalent two dimensional roughness element spacing of about three particle diameters in contrast to tidal flows over rippled sand beds the roughness lengths for sandy gravels remained relatively constant throughout the tidal cycle furthermore these measurements provided no systematic evidence of the effects of flow acceleration on profilederived estimates of the friction velocity u and the roughness length z0

deep water facies processes and models a review and classification scheme for modern and ancient sediments abstract a review of previous work on modern and ancient deep water facies processes and models is presented with a new classification scheme involving 40 distinct facies related to 15 conceptually distinct facies groups these facies are fixed points in a spectrum of facies generated in a process continuum from resedimentation processes through semi permanent bottom currents to pelagic settling in essence the scheme is descriptive of the sedimentary attributes of sediments although it is designed to aid interpretation of possible sediment transport deposition processes the classification scheme is three tier with facies classes groups and constituent facies and is hierarchical to allow flexibility in its use there are seven facies classes with classes a e defined largely on the basis of grain size differences class f on the basis of internal organization and class g on composition the facies classes are class a gravels muddy gravels gravelly muds and pebbly sands with 5 gravel grade class b sands with 80 sand grade and 80 mud 40 silt and 0 20 sand class e muds and clays with 95 mud grade for the purpose of large scale mapping or reconnaissance fieldwork either the level of facies classes or groups may be appropriate whereas for more detailed sedimentology the more detailed facies level will be necessary

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

formation of fluidization pipes during liquefaction examples from the uratanna formation lower cambrian south australia usually well preserved fluidization pillars and sand filled fluidization pipes occur within submarine channel sands of the basal uratanna formation lower cambrian in the adelaide geosyncline of south australia the morphology of these structures reflects complex lateral and vertical movement of fluids during liquefaction and dewatering fluidization pipes acted as conduits for highly concentrated upward directed fluid flow the formation and maintenance of these pipes was dependent upon the development of a pipe wall composed of clay plugged fine sand formed during initial fluidization this lining acted as a permeability barrier confining and concentrating fluidized flow within the pipe each of the pipes is surrounded by a cylindrical fluidization halo in which leakage through the pipe lining produced partial fluidization of the surrounding sediment fine scale structures within these haloes indicate that fluids flowed radially and upward out of the fluidization pipes at an acute angle these fluids merged with and influenced the orientation and size of adjacent fluidization pillars the fluidization pipes of the uratanna formation may represent unusual preservation of the unstable fluid flow conditions that occur during incipient fluidization of sand beds

late quaternary deltaic lowstand wedges on the rhone continental shelf france abstract shallow seismic profiles on the rhone continental shelf have shown the existence of stacked progradational lowstand wedges on the outer shelf accumulated during late quaternary glacioeustatic lowstands the wedges are bounded by sharp to erosional sequence boundaries and onlap onto the middle shelf the thickness of individual wedges attains 50 meters at the shelf edge where they are sheared by slumping the wedges exhibit well developed progradational clinoforms episodically interrupted by internal unconformities on which there is a downward shift of the succeeding clinoforms these represent small scale in the order of a few meters falls in sea level during the quaternary eustatic cycles the durations of the stable highstand conditions appear to have been too brief to permit the regressive highstand tract to prograde to the outer shelf therefore the shelf edge builds up entirely with lowstand wedges

shallow marine massive sandstone sheets as indicators of palaeoseismic liquefaction an example from the ordovician shelf of central bolivia abstract the middle to upper ordovician siliciclastic succession in central bolivia provides excellent exposures of up to 1 m thick massive sandstone beds produced by liquefaction induced sediment remobilisation these fine grained massive sandstones occur in shallow marine nearshore facies that were deposited above storm wave base vertical to steeply inclined clastic dykes which penetrate up to 1 5 m of the overlying sediment pile feed into the basal parts of massive sandstone sheets these dykes are interpreted as pathways used by liquefied sediment during upward directed escape from a subsurface horizon the relatively short lateral spacing of 5 to 25 m between the individual dykes initiated lateral coalescence of ejected individual sediment bodies as a result massive sandstone sheets formed and can be traced laterally over several kilometres while undeformed sandy deposits contain between 5 to 10 dispersed clay the average clay content in massive sandstone sheets is 15 the elongated sometimes s shaped form of the sandy laminated fragments reflects squeezing during movement showing that they have been deformed under shear stress during flow the axis of maximum elongation of the fragments indicates local flow direction as the massive sandstone sheets are likely the products of seismic shocks they provide the first evidence of tectonic activity in this part of the basin during the middle to late ordovician

anatomy of shelf deltas at the edge of a prograding eocene shelf margin spitsbergen although shelf edge deltas are well imaged seismic features of holocene and pleistocene shelf margins documented outcrop analogues of these important sand prone reservoirs are rare the facies and stratigraphic architecture of an outcropping shelf edge delta system in the eocene battfjellet formation spitsbergen is presented here as well as the implications of this delta system for the generation of sand prone shelf margin clinoforms the shelf edge deltas of the battfjellet formation on litledalsfjellet and hogsnyta produced a 3 5 15 km shelf edge attached slope apron 70 m of sandstones proximally tapering to zero on the lower slope the slope apron consists of distributary channel and mouth bar deposits in its shelf edge reaches passing downslope to slope channels chutes that fed turbiditic lobes and spillover sheets in the transgressive phase of the slope apron estuaries developed at the shelf edge and these also produced minor lobes on the slope the short headed mountainous rivers that drained the adjacent orogenic belt and fed the narrow shelf and the shelf edge position of the discharging deltas made an appropriate setting for the generation of hyperpycnal turbidity currents on the slope of the shelf margin the abundance of organic matter and of coal fragments in the slope turbidites is consistent with this notion evidence that many of the slope turbidites were generated by sustained turbidity currents that waxed then waned includes the presence of scour surfaces and thick intervals of plane parallel laminae within turbidite beds in the slope channels and thick spillover lobes with repetitive alternations of massive and flatlaminated intervals the examined shelf edge to slope system now preserved mainly below the shelf break and dominated by sediment gravity flow deposits has a threefold stratigraphic architecture a lower progradational part in which the clinoforms have a slight downward directed trajectory a thin aggradational zone and an upper part in which clinoforms backstep up onto the shelf edge a greatly increased density of erosional channels and chutes marks the regressive to transgressive turnaround within the slope apron and this zone becomes an angular unconformity up near the shelf edge this unconformity with both subaerial and subaqueous components is interpreted as a sequence boundary and developed by vigorous sand delivery and bypass across the shelf edge during the time interval of falling relative sea level the studied shelf margin clinoforms accreted mostly during falling stage sea level below the shelf edge but the outer shelf later became estuarine as sea level became re established above the shelf edge

recumbent flame structures in the lower gondwana rocks of the jharia basin india a plausible origin abstract a set of recumbent flame structures was found within a stacked channel complex belonging to the raniganj formation upper permian of the lower gondwana sediments of the jharia basin india the characteristics particularly the relation with the erosional base of the overlying channel the nature of the host layer and the geometry of the flame structures suggest that the horizontal gradient in pore fluid pressure developed within the concealed layer in response to the differential loading due to partial removal of the overburden during erosional incision was responsible for triggering the static liquefaction of the sediments and the density driven deformation of the sand mud interface took place rounded excrescence of sand bulged downward into the underlying mud which in turn was projected upward in the form of sharp flames following the trajectory of the pore fluid gradual bending of the flow trajectory towards the horizontal direction due to the presence of the overlying impermeable mud layer led to the development of the recumbent geometry of the flame structures

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

evaluation of planetary boundary layer simulation in gfdl atmospheric general circulation models abstractthis study describes the performance of two geophysical fluid dynamics laboratory gfdl atmospheric general circulation models agcms in simulating the climatologies of planetary boundary

seismically induced soft sediment deformation structures in the palaeogene deposits of the liaodong bay depression in the bohai bay basin and their spatial stratigraphic distribution abstract soft sediment deformation structures ssds have been identified from well cores in the palaeogene deposits of the liaodong bay depression in the bohai bay basin china these deposits formed as interbedded sand and mud at a delta front or on the slope toe of the prodelta according to criteria proposed by previous research we established that these ssds were induced by earthquakes and that they can be divided into two groups ductile deformation structures plastic intrusions ball and pillow structures flame structures boudinage structures irregular convolute stratifications and synsedimentary faults and folds and brittle deformation structures sand dykes and autoclastic breccias based on their level of deformation size and complexity the ssds were divided into three groups from weak to strong to reflect the intensity of palaeo earthquakes with consideration of the palaeo sedimentary environment we proposed a model to account for the production and preservation of these ssds according to the classification adopted in this study and the spatial stratigraphic distribution of the ssds the tectonic activities of the tan lu faults in the bohai bay basin were investigated the a and b oilfields assumed names are located in the tectonically active zones of the west and east branches of these faults respectively the extension tectonic activities in the a oilfield region exhibit a sharply decreasing trend from e2s3 to e2s1 and increase again in e3d2 whereas the strike slip tectonic activities in the b oilfield region exhibit an increasing trend from e2s3 to e2s1 and finally reach a maximum to e3d3 the results of this study show that the method of analysis of the spatial stratigraphic distribution of ssds is suitable for determining the evolution of tectonic activity and thus it can provide a new perspective for basin analysis

experimental soft sediment deformation structures formed by the liquefaction of unconsolidated sands and some ancient examples the effects of liquefaction in saturated sand bodies under a variety of driving forces are described from shaking table experiments and structures from the geological record are presented which are analogous to the experimental structures the collapse of sloping heaps of cross bedded sand under a gravitational body force generates low angle essentially uncontorted stratification a basal zone of shearing may be present with steepened and folded foresets stretching of foresets may be accommodated on normal faults and bottomsets may be contorted into inclined folds in natural systems the substrate may also liquefy causing deformation driven by an unevenly distributed confining load stratification in the surface bedform is flattened and stratification in the substratum contorted experiments failed to produce relative displacement at the interface between stacked sand bodies liquefaction of gravitationally unstable systems in sands generates load structures comparable to those from sand mud systems recumbent folded deformed cross bedding is formed by current shear over a liquefied bed as has been inferred from field and theoretical analyses shear of nonliquefied sand forms angular folds other deformation mechanisms such as fluidization or seepage may generate structures similar to all of these local water escape structures driven by fluidization occur in the upper parts of some liquefied sand bodies they include cusps sand volcanoes and clastic dykes transient cavities formed in some experiments and seemed to be preserved as breached cusps although the experiments tried to isolate individual driving forces driving forces may operate together and there may be a continuum between deformation driven by water escape and deformation driven by loading different structures from those described here may form where liquefaction develops in a buried layer as opposed to at the sediment surface

eustatic and tectonic control on the distribution of marine seismites examples from the upper ordovician of kentucky usa abstract widespread zones of soft sediment deformation are not ubiquitous throughout the rock record rather they are associated with orogenic sediments and are concentrated in specific portions of depositional sequences characterized by deformation prone facies upper ordovician soft sediment deformation features exposed in kentucky are here interpreted as the result of seismically induced thixotropic fluidization of muds resulting in foundering of denser silts and carbonate sands and corresponding diapiric injection of muds severity of soft sediment deformation is associated with sediment density gradients bed thicknesses and varying magnitudes of triggering events the widespread nature 5000 km 2 of multiple deformation horizons argues for a seismic trigger resulting from reactivation of multiple basement faults eight large scale 3rd order depositional sequences were examined for the presence of specific deformation features and stratigraphic position of those intervals the regular distribution of deformation prone facies throughout the upper ordovician seems to have been regulated by eustatic fluctuations seismicity generated by far field tectonics provided the triggering mechanism to disrupt deformation prone strata the record of seismites and their co occurrence with k bentonites provides a meter of intensity and timing of tectophases of the taconic orogeny

turbidite variability and architecture of sand prone deep water slopes eocene clinoforms in the central basin spitsbergen abstract the architecture and turbidite variability within six wedge shaped downslope thinning sand prone slope accumulations are documented from eocene shelf margins on spitsbergen the central basin formed as a small foreland or piggy back basin and the studied turbidites accumulated mainly on the slope portion of sand prone clinoforms that developed during depocenter migration and infilling of the basin the shelf margin clinoforms have amplitudes minimum water depths from 100 to 350 meters and their shelf slope and basin floor segments are well imaged and can be walked out along many of the mountainsides only a small percentage of the clinoforms are sand prone and these developed when sea level occasionally fell to or below the shelf edge of the sand prone clinoforms some had their sand budget partitioned mainly out onto the basin floor basin floor fans but most trapped the sand on the slope only the latter are now visible as downslope thinning wedges some 2 5 3 5 km in downdip extent the turbidites within this type of clinoform have been examined and classified the lower slope to base of slope segment of the studied clinoform complexes are dominated by lobes consisting of broad shallow channels and sheet like turbidites becoming heterolithic and muddy out on the basin floor beds on the lower slope vary from thick up to 4 5 meters ungraded or laminated sandstones to thinner ungraded sandstones with coarse cappings the middle slope segment of clinoform complexes is dominated by narrow channels chutes that feed downslope to progradational chute mouth lobes chutes contain ungraded and laminated sandstone beds up to 3 m thick whereas the chute mouth lobes show alternations of thinner ungraded to laminated or rippled sandstones these lobes become more heterolithic and muddy downslope the shelf edge to upper slope segment of clinoform complexes is dominated by upward coarsening and thickening sheetsands of steep fronted shelf edge deltas the sandsheets of the delta front can be traced updip into mouth bar and distributary channel sandstones it is argued that shelf margin accretion represented by the sand prone slope wedges was achieved mainly by sand laden currents that flooded from the shelf edge as hyperpycnal flows this hypothesis is supported by 1 the direct connection between channel and mouth bar systems at the shelf edge and the turbidites of the slope lobes 2 the systematic progradational character of the slope lobes 3 the absence of large scale slump scars gullies or canyons on the slope and 4 the dominance of a type of turbidite that implies deposition from sustained flow detailed examination of the architecture of one of the slope wedges shows that there are unconformities developed within the stratigraphy below the shelf edge and that these erosional terraces beheaded the deltas perched on the uppermost slope the erosion surfaces indicate fall of sea level to this position despite the magnitude of this fall up to 80 meters the lack of canyons on the slope prevented the construction of basin floor fans such falls of sea level on non canyoned slopes simply promote sand prone accretion of the shelf margin

upper wilcox rosita delta system of south texas growth faulted shelf edge deltas the rosita delta system a heretofore unrecognized major depositional system preserved in the deep upper wilcox of south texas was delineated by detailed correlation of approximately 500 well logs the rosita delta system comprises at least three delta complexes each of which can be traced up to tens of miles along strike and up to approximately 15 mi 24 km downdip basinward across the growth fault zone each delta complex thickens from about 600 ft 180 m to more than 3 000 ft 900 m the growth faults were activated by progradation of deltas over unstable prodelta slope muds at the contemporary shelf margin the three upper wilcox delta complexes studied in detail are from oldest to youngest the duval zapata and live oak deltas named for the counties in which they are centered each complex consists of several lobes some of which can be traced across the deep zones where the thickness increases by as much as tenfold owing to progradation over active growth faults characteristic coarsening upward progradational units are interpreted from electric log patterns to include prodelta shales delta front sandstones distributary channel and channel mouth bar sandstones and interdistributary shales and sandstones appreciable variability in sandstone distribution in the deltas may reflect changing importance of fluvial versus marine currents in distributing sediment along the delta front however all of the deltas prograded abruptly toward the shelf margin the gulfward extent of these delta complexes is unknown and it is concluded that appreciable quantities of sandstone remain to be explored in the deep subsurface of the trend

soft sediment deformation structures interpreted as seismites in middle late pleistocene aeolian deposits apulian foreland southern italy abstract soft sediment deformation structures in middle late pleistocene deposits of torre san gennaro brindisi southern italy have been analysed from a morphologic point of view the deformational structures are represented by deformed cross bedding and large injection structures they are restricted to aeolian sediments and the mechanism of deformation is related to liquefaction and or fluidization processes the liquefaction and or fluidization processes have been interpreted as seismic induced after consideration of all other possible trigger agents the discussion about the possible source areas of the palaeoseismic event was carried out through the analysis both of the general magnitude distance relations and the main structural features of the study zone in conclusion we consider the key criteria for trigger mechanism interpretation of soft sediment deformation structures in aeolian deposits and the actual feasibility of using aeolian sediments for the palaeoseismic studies

aseismic controls on in situ soft sediment deformation processes and products in submarine slope deposits of the karoo basin south africa intervals of soft sediment deformation features including vertical fluid escape and load structures are common and well exposed in permian lower slope deposits of the tanqua depocentre karoo basin the structures mainly comprise elongated flames and load structures associated with ruptured sandstones and structureless siltstones observed over a range of scales the presence of an upper structureless siltstone layer linked to the flames interpreted as a product of the debouching of fine grained material transported through the flame onto the palaeo seabed together with the drag and upward folding of lower sandstone layers is evidence that the flames were formed in situ by upward movement of sediment rich fluids flames are oriented parallel to the deep water palaeoslope in lateral splay deposits between two major slope channel complexes statistical correlation and regression analyses of 180 flame structures from seven stratigraphic intervals suggest a common mechanism for the deformation and indicate the importance of fluidization as a deformation mechanism importantly deformation occurred in an instantaneous and synchronous manner liquefaction and fluidization were triggered by incremental movement of sediment over steeper local gradients that were generated by deposition of a lateral splay on an inherited local north west facing slope seismic activity is not invoked as a trigger mechanism because of the restricted spatial occurrence of these features and the lack of indications of earthquakes during the time of deposition of the deep water succession the driving mechanisms that resulted in the final configuration of the soft sediment deformation structures involved a combination of vertical shear stress caused by fluidization development of an inverse density gradient and a downslope component of force associated with the local slope ground penetrating radar profiles confirm the overall north east orientation of the flame structures and provide a basis for recognition of potential larger scale examples of flames in seismic reflection data sets

slope failure dynamics and impacts from seafloor and shallow sub seafloor geophysical data case studies from the costa project holocene and slightly pre holocene submarine landslide are found both in high latitude glacial dominated margins and in lower latitude river dominated margins this paper constitutes a major assessment on some of the best studied submarine instabilities in the world we review and update from original data and literature reports the current state of knowledge of storegga traenadjupet and finneidfjord slides from the mid norwegian margin afen slide from the faeroe shetland channel big 95 slide and central adriatic deformation belt cadeb from continental slope and inner continental shelf settings off the ebro and po rivers in the mediterranean sea canary slide west of the westernmost youngest canary islands and gebra slide off the northern tip of the antarctic peninsula in the southern hemisphere i e those studied in the continental slope stability costa project the investigated slides range in size from the gigantic 90 000 km2 and almost 3000 km3 storegga slide to the tiny 1 km2 and 0 001 km3 finneidfjord slide not only do individual submarine landslides rarely involve processes precisely fitting with pre established categories mostly based on subaerial research but also they display complex mechanical behaviors within the elastic and plastic fields individual events can involve simultaneous or successive vertical to translational movements including block detachment block gliding debris flow mud flow and turbidity currents the need for an in depth revision of the classification criteria and eventually for a new classification system based on the new imaging capabilities provided by modern techniques is more than obvious we suggest a new system which for the moment is restricted to debris flows and debris avalanches volume calculation methods are critically reviewed and the relations between some key geomorphic parameters are established for the selected slides the assumed volume missing from scar areas does not necessarily match the actual volume of sediment remobilised by an individual event since in situ sediment can be remoulded and eventually incorporated during the slide downslope journey cadeb a shore parallel prodelta detached from its source is the exception to the good correlation found between across slope width and alongslope length with slide area height drop measured from the headwall upper rim to its foot correlates with the debris deposit maximum thickness unless the slide moves into restricted areas which prevent farther forward expansion of the deposit such as gebra and big 95 in such cases over thickened deposits are found a particularly loose and fluid behavior can be deduced for slides showing an over thinned character such as the canary slide that traveled 600 km scar areas and slip planes have been investigated with particular emphasis although slide headwalls might present locally steep gradients up to 23 for storegga slide the slope gradients of both the failed segment margins and the main slip planes are very low max 2 and usually around 1 and less an exception is the finneidfjord slide 20 5 that occurred in 1996 because of a combination of climatic and anthropogenic factors leading to excess pore pressure and failure mechanically distinct low permeable clayey weak layers often correspond to slip planes beyond the slide headwall since not only formation of these weak layers but also sedimentation rates are climatically controlled we can state that slide pre conditioning is climatically driven too run out distances reflect the degree of disintegration of the failed mass of sediment the total volume of initially failed material and transport mechanisms including hydroplanning commonly specific run outs could be attributed to distinct elements such as cohesive blocks and looser matrix as nicely illustrated by the big 95 slide total run outs usually correspond to matrix run outs since the coarser elements tend to rest at shorter distances outrunner blocks are finally a very common feature proving the ability of those elements to glide over long distances with independence of the rest of the failed mass in addition to pre conditioning factors related to geological setting and sedimentation conditions a final trigger is required for submarine landslides to take place which is most often assumed to be an earthquake in high latitude margins earthquake magnitude intensification because of post glacial isostatic rebound has likely played a major role in triggering landslides although it cannot be totally ruled out there is little proof at least amongst the costa slides that gas hydrate destabilisation or other processes linked to the presence of shallow gas have acted as final triggers

distribution of soft sediment deformation structures in clinoform successions of the permian ecca group karoo basin south africa abstract the stratigraphic distribution of two groups of soft sediment deformation structures ssds detached dominated by lateral movement forming slides and slump deposits and debrites and in situ dominated by vertical movement forming flame structures pseudonodules and ball and pillow structures are compared in two permian successions in the tanqua and laingsburg depocentres of the karoo basin ssds occur in a series of well exposed 40 to 55 m thick sedimentary cycles cycle thicknesses decrease upwards and the proportion of deformed strata is around 30 in both successions each flooding surface bounded cycle is characterized by a lower unit dominated by thin bedded turbidites overlain by an intermediate section dominated by soft sediment deformed facies above which are undeformed thick bedded mouthbar and shoreface sandstones the upper part of each cycle fines upwards into thin bedded turbidites which are overlain by the cycle bounding flooding surface the cycles and the distribution of ssds are the response to delta outbuilding and retreat over a clinoform rollover and onto a clinoform slope repeatable trends in the distribution of ssds during the evolution of clinoforms in both depocentres indicate a level of stratigraphic organisation and predictability in the otherwise complicated record of processes around the clinoform rollover

architecture of a channel complex formed and filled during long term degradation and entrenchment on the upper submarine slope unit f fort brown fm sw karoo basin south africa abstract an exhumed upper slope channel complex composed of four channels that have a range of sedimentary fill styles has been investigated with the emphasis on understanding lithology distribution in space and time initiation of the channel complex which forms part of a seismic scale channel complex set is marked by a basal erosion surface interpreted to have been carved by multi event erosive sediment gravity flows which bypassed sediment down dip farther into the basin in this phase deposits are restricted to slides slumps from the conduit margins waning of this high energy phase is represented by limited deposition of scour based sandstone and claystone clast conglomerates which fine and thin upward into bedded siltstone prior to channel abandonment this erosion then deposition cycle represents the record of the first channel fill within the channel complex the cycle is restarted with another phase of erosion and sediment bypass followed by deposition which makes up the second channel fill this process is repeated two more times to form the third and fourth channel fills however the depth of erosion decreases upward in the successive channel fills the four sub vertically offset stacked single channel fills comprise a channel complex formed during a period of waxing to waning energy as they are partially removed by a deeply entrenched 100 m slope valley the channel fills represent a remnant of an overall waxing period degradational phase at the scale of a depositional sequence comparison with published examples of slope channel complexes suggests that many features interpreted in 3d seismic data as single channels are in fact channel complexes which has major implications for the appraisal of internal heterogeneities in these reservoir types

a sequence of soft sediment deformation dewatering structures in late quaternary subaqueous outwash near ottawa canada abstract a sequence of soft sediment deformation structures occurs in late quaternary sediments near ottawa canada the sediments are attributed to deposition on subaqueous outwash fans in the champlain sea at the submerged front of the retreating wisconsin glacier in upward sequence the deformed units comprise convolute stratification ball and pillow structures and dish structures deformation is attributed to slumping on the subaqueous fans and or to the melt out of ice blocks which had been buried by fan sediments the sequence of structures is interpreted in terms of a series of events as follows 1 1 local fluidization of low permeability sediments formed convolute stratification disrupted anticlines acted as vertical diapirs through which fluidized sediment ascended 2 2 the diapirs penetrated overlying more cohesive sediments forming ball and pillow structures 3 3 dish structures formed in silty fine sand which had passed upward through the diapirs and between the ball and pillow structures in some cases the silty sand moved downslope as a liquefied sediment flow and dish structures were deformed to give oval plan forms with long axes normal to the local paleoslope

anatomy of a water escape cusp in upper proterozoic torridon group sandstones scotland abstract evidence from recently published experiments is applied to the interpretation of a typical soft sediment deformation structure in coarse fluvial sandstones from the applecross formation of the upper proterozoic torridon group in northwest scotland the structure is an interfacial cusp formed at the contact between two cross bedded sandstone units in an upward coarsening sequence the characteristics of the structure suggest that deformation took place while the sediment was in a fluidized state during fluidization a water filled cavity developed near the top of the lower unit separating fluidized sediment beneath from a static couplet above the cavity became narrower and taller as fluidization continued focussing fluidization at a point primary stratification was destroyed in the fluidized zone but there is no evidence that fluidized sediment burst through the overlying zone a rupture may be out of the plane of the section or alternatively fluidization could have stopped before this stage was reached or fluid pressures could have been dissipated upwards the cavity closed leaving the lower part of the static couplet as a distinct unit estimates of the fluidization velocity and the duration of fluidization suggest the volume of water required for fluidization this could have been derived from packing changes following liquefaction of underlying sediment or from groundwater movements within the braided fluvial environment

river dominated shelf edge deltas delivery of sand across the shelf break in the absence of slope incision shelf edge deltas record the potential magnitude of sediment delivery from shallow water shelf into deep water slope and basin floor and if un incised represent the main increment of shelf margin growth into the basin for that period the three dimensional complexity of shelf edge delta systems and along strike variability at the shelf edge in particular remains understudied the permian triassic kookfontein formation of the tanqua karoo basin south africa offers extensive three dimensional exposure 100 km2 and therefore a unique opportunity to evaluate shelf edge strata from an outcrop perspective analysis of stratal geometry and facies distribution from 52 measured and correlated stratigraphic sections show the following i in outer shelf areas parasequences are characterized by undeformed river dominated storm wave influenced delta mouth bar sandstones interbedded with packages showing evidence of syn depositional deformation the amount and intensity of soft sediment deformation increases significantly towards the shelf edge where slump units and debris flows sourced from collapsed mouth bar packages transport material down slope ii on the upper slope mouth bar and delta front sandstones pinch out within 2 km of the shelf break and most slump and debris flow units pinch out within 4 km of the shelf break iii further down the slope parasequences consist of finer grained turbidites characterized by interbedded thin tabular siltstones and sandstones the results highlight that river dominated shelf edge deltas transport large volumes of sand to the upper slope even when major shelf edge incisions are absent in this case transport to the upper slope through slumping debris flows and un channellized low density turbidites is distributed evenly along strike

control of syndepositional faulting on systems tract evolution across growth faulted shelf margins an analog experimental model of the miocene imo river field nigeria the presence of growth faults on shelf margin deltas complicates the sequence stratigraphic interpretation of deltaic successions this article describes an analog modeling study of a growth faulted shelf margin delta the aim of the project was to obtain a better understanding of the depositional architecture on a systems tract scale on both sides of the growth fault and to evaluate possible hydrocarbon trapping configurations in such successions the analog flume experiment incorporated the combined effect of growth faulting regional subsidence and eustasy on hanging wall and footwall blocks experimental variables were based on seismic and well data of the imo river field in the niger delta which was used as a prototype to calibrate the experimental results the spatial scale of the model in conjunction with the supply rate result in a time scaling that models basin fill processes that operated over more than 5 m y in 90 hr of experiment digital topography scans required for the determination of the bulk sediment transport were made of the landscape at preset time intervals the resultant experimental sedimentary successions on both sides of the growth faulted shelf margin were sliced and correlated across the fault the results first were compared to the imo river field prototype and subsequently to examples from the gulf coast and to extensional basin settings these comparisons led to the formulation of a conceptual sequence model for growth faulted margins that relates the systems tract distribution on each side of the fault to eustasy the hanging wall succession is composed of falling stage lowstand and early transgressive deposits the footwall succession in contrast is characterized by late transgressive incised valley fill and highstand deposits the conceptual sequence model provides useful analogs for common and several alternative hydrocarbon trapping configurations in growth faulted settings