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

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

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

the effect of topography latitude and lithology on rock glacier distribution in the lemhi range central idaho usa abstract statistical analysis of rock glaciers in the lemhi range demonstrates that their development and preservation is controlled primarily by annual insolation and lithology we inspected 171 alpine valleys in the lemhi range using optical remote sensing techniques digital topographic analysis and field examination in those valleys we identified 48 rock glaciers and examined them for lichen cover evidence of ice presence specific evidence of movement and distinctive morphological features in addition to recording the presence or absence of a rock glacier in each alpine valley existing rock glaciers were classified according to their morphology factors such as topographic shading lithology relief aspect and elevation determine the development and preservation of rock glaciers analysis of these factors in the lemhi range shows that elevation 2600 m a north facing aspect 300 60 and multivariate statistical analysis of controlling parameters demonstrates that annual insolation and latitude influence rock glacier occurrence most strongly whereas duration of insolation is a logical controlling factor latitude is more enigmatic additional statistical analysis indicates that the latitude factor is likely a reflection of lithologic changes with latitude along the range lithology may affect rock glacier distribution through its effects on hydrology or air ventilation moreover statistical analysis shows that rock glacier occurrence correlates with protalus lobe occurrence suggesting that protalus lobes play a role in the genesis of rock glaciers in the lemhi range separate analysis of the classification systems shows that each morphologic class inferred to correlate with rock glacier activity is statistically significant and distinguishable from other classes in addition to the effect of insolation statistical analysis of the classification system also shows that latitude influences distribution of existing rock glacier classes independent of lithology

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

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

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

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

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

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

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

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

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

kyanite eclogite to amphibolite fades evolution of hydrous mafic and pelitic rocks adula nappe central alps in the southern adula nappe central alps two stages of regional metamorphism have affected mafic and pelitic rocks earlier eclogite facies with a regional zonation from glaucophane eclogites to kyanite hornblende eclogites was followed by a tertiary overprint which varied from greenschist to high grade amphibolite facies despite a common metamorphic history contrasting equilibration conditions are often recorded by high pressure mafic eclogite and adjacent predominantly lower pressure pelite assemblages this pressure contrast may be explained by different overprinting rates of the two bulk compositions during unloading the rates are controlled by a mechanism in which dehydrating metapelites provide the h2o required for simultaneous overprinting of enclosed mafic eclogites by hydration

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

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

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

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

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

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