grain fabric of experimental gravity flow deposits abstract grain fabric of deposits accumulated from a high density surge type gravity turbidity current in an experimental flume was measured vertical sequential change 0 2 mm interval in imbrication shows that a bed can be divided into lower middle upper and uppermost parts the lower part is characterized by both up current and down current imbrication with a wide range of angles dominant up current imbrication and rare down current imbrication characterize the middle part the imbrication angle of this part tends to be smaller than in the lower part the upper part is represented by intervals with up current imbrication nearly flat imbrication is dominant in the uppermost intervals statistically significant preferred orientation was observed from the lower middle and upper parts and it deviates up to 13 in both clockwise and anticlockwise directions from the current direction the lower and middle parts of the bed may correspond to the bouma a division judging from the wider range of imbrication angles and the presence of down current imbrication which have been reported from natural turbidite beds the upper part which is characterized by up current imbrication is interpreted to be the bouma b division the uppermost interval may coincide with the d division the episodically appearing down current imbrication in the lower and middle parts can probably be attributed to oscillation of an interface between a denser basal layer and superjacent low density layer of the turbidity current measurement of grain orientations in this and previous studies implies that at least 30 of deviation from the flow axis should be considered for paleoflow analyses based on grain fabrics

controls on focused flow and dispersed flow deepwater carbonates miocene agua amarga basin spain abstract common models for carbonate slope or basin margin sedimentation emphasize the contrasts between linear sediment sources and point sediment sources geologic mapping and high resolution stratigraphic study of a set of miocene outcrops exceptional for their three dimensional exposure and preservation of paleotopography demonstrates that paleotopographic focus or lack thereof may be a dominant control on geometries and sediment character of sediment gravity flow deposits in line sourced systems in the agua amarga basin se spain basin topography is initially modified by subaerial exposure and erosion of volcanic basement to form paleovalley systems after late miocene marine inundation topography is partially modified by infilling of high energy shallow water heterozoan deposits units 1 and 2 that subdued topography in one area to produce a ramp like surface but did not significantly infill a large paleovalley located in another area further relative rise in sea level resulted in an extensive reefal platform that formed along a paleo high adjacent to both features la rellana platform subsequent sediment gravity flow deposits shed from this reefal platform followed two pathways down the ramp like surface dispersed flow or into the large flooded paleovalley focused flow deposits within each system display contrasting lithofacies architectures these deepwater deposits units 3 7 in this study consist of carbonate breccia facies coarse facies graded skeletal packstone facies coarse facies and planktonic foraminifera rich facies fine facies that are interpreted as sediment gravity flow deposits and pelagic sediments relative sea level fluctuations resulted in deepwater facies variations in the large paleovalley as a result of significant backstepping and progradation of the rellana reefal platform on a gently sloping surface fining of basinal deposits and shelfward migration of the locus of deposition for sediment gravity flows is associated with sea level rise coarsening of basinal deposits and basinward migration of the locus of deposition for sediment gravity flows is associated with stillstand and relative fall in sea level both relationships demonstrate a direct link between the locus of reefal platform growth and style of basin sedimentation early parts of relative rises in sea level late parts of highstands and falling stages led to transport of abundant coarse sediment into the basin focused flow deposits were line sourced and funneled into the axis of a large margin parallel paleovalley and confined to a channel volume ratio of coarse facies to fine facies is estimated at 0 7 deposits in proximal paleovalley locations display compensation geometries around positive relief on debrites channelization erosional truncation lapout against paleovalley walls and some drape as a result of lateral confinement and proximity to the sediment source deposits in distal paleovalley locations display increasingly tabular geometries as a result of decreasing lateral confinement and concentration of coarse grained sediment gravity flows down depositional dip dispersed flow deposits were line sourced into the basin along a gently inclined ramp like surface that lacked paleotopographic focus volume ratio of coarse facies to fine facies is estimated at 0 1 the less complex sheet like depositional geometries and locations of these deposits result from the absence of lateral confinement and subtle changes in substrate slope focused flow sediment gravity flow deposits that are confined by topographic elements such as channels are most likely to form sizeable accumulations of coarse facies with characteristics most appropriate for conventional oil and gas exploration there are many paleotopographic configurations that can lead to focusing of flows so this deepwater carbonate system may be more common than previously recognized

origin dimensions and distribution of remobilized carbonate deposits in a tectonically active zone eocene thebes formation sinai egypt abstract determination of the distribution and mechanism for carbonate dominated mass transport sediments is often compromised by the scale and access to exposures consequently many studies lack the resolution to capture the heterogeneity and dimensions of mass transport deposits this study documents the size shape and stratal assemblage of remobilized carbonates in the eocene thebes formation in the hammam faraun fault block hffb of western sinai revealing the complexities of carbonate mass transport deposits at sub seismic scale present day pseudo three dimensional exposure of the thebes formation in a large fault block formed during the opening of the gulf of suez allowed for lateral and down dip measurement of slope and basinal facies in the field and from photos remobilized facies were digitized in the photos and evaluated using image analysis software a technique with a wide range of applications to outcrop studies of sedimentary architecture debris flow deposits in the lower section of the thebes formation comprises clasts with differing fossil assemblages a relative sea level rise at the start of upper thebes formation deposition resulted in basinal sediments comprising periodic incursions of high density turbidite grainstones encased within a background of planktonic foraminiferal wackestones foraminiferal assemblages of remobilized facies imply multiple sources on the carbonate platform demonstrating the effect of short lived tectonism on slope instability and deposition of mass transport deposits the results of the study confirm that tectonism associated with the syrian arc fold belt which altered the style of basin sedimentation between egypt and syria persisted into the eocene at least as far south as wadi araba in the western desert and hammam faraun in sinai in addition the shape size and extent of the two dominant remobilized facies debris flows and grainstone turbidites are influenced by their mud rich versus grainy compositions

seismic architecture of a lower cretaceous platform to slope system santa agueda and poza rica fields mexico two three dimensional seismic data sets over the albian western golden lane margin and time equivalent basinal deposits of poza rica field allowed us to investigate the linked architecture of a steep sided carbonate platform el abra formation and a thick accumulation of redeposited carbonate sediment at the toe of the slope and in the basinal area tamabra formation regional seismic cross sections show that the most aggrading albian platform has an eroded platform top a scalloped margin and a channelized slope that are equivalent to a 20 km 12 4 mi wide westward thinning thick toe of slope apron made of chaotic contorted mounded moderate to high amplitude reflections detailed reflection geometries in the albian toe of slope and basinal deposits consist of chaotic to short discontinuous low amplitude reflection at the toe of the slope of the golden lane platform laterally changing to a discontinuous mounded shingling reflection which ultimately turns into high amplitude parallel reflections we interpret this lateral change to reflect the seismic signature of the change from the block and debris flow dominated toe of slope area to debris flow and concentrated density flow deposits in the basin that ultimately grade laterally into pelagic deposits on a flattened seismic slice mounded reflections correspond to lobate to fan shaped seismic events several kilometers wide that are interpreted as a carbonate basin floor fan comparison between core and seismic data shows a dominance of debris flows in the lower two albian sequences albian 1 and albian 2 that grade vertically into more lobate concentrated density flows and turbidites in the upper two albian sequences albian 3 and albian 4 seismic data used in this study combined with core observations do not support the interpretation of the albian tamabra formation being of shallow water origin seismic features identified as basin floor fan channel and debris flow deposits have a shape and size that are similar to those of other redeposited basinal carbonate deposits elsewhere the seismic architecture shows that the poza rica field is a typical example of thick accumulation of grainy porous carbonate deposits in a basinal setting this example shows the potential of a large hydrocarbon accumulation in a tectonically modified stratigraphic trap around shallow water carbonate platforms

coarse carbonate breccias as a result of water wave cyclic loading uppermost jurassic south east basin france in the uppermost jurassic of the central part of the south east basin of france an association of lime mudstone beds calcarenite beds and coarse carbonate breccia bodies form an informal stratigraphical unit called the barre tithonique in the barre tithonique gradual transitions from lime mudstone or calcarenite to breccia show different stages of deformation leading to progressive brecciation of the original lithologies the study of the breccia facies and the observed gradual transitions as a whole document a new early diagenetic process in carbonate environments resulting from water wave and seabed interaction water wave induced brecciation and its abundance in the barre tithonique indicate that sea seabed interaction was significant comparison with modern studies of the mechanics of wave seabed interaction suggests that water depth was less than 200 m it is demonstrated that sedimentary features such as channel like structures previously interpreted as being the result of erosion and deposition of mud flows were in fact produced by wave induced in situ reworking of lime mud without any significant unidirectional flow or gravity induced displacement

quantitative characterization of carbonate pore systems by digital image analysis a new method of digital image analysis can quantify pore parameters over more than three orders of magnitude from a submicron to a millimeter scale this porosity characterization does not require knowledge of lithology age burial depth or diagenesis of the sample the method is based on digital analyses of images from thin sections at variable magnifications taken under an optical microscope om and under an environmental scanning electron microscope esem the results help explain variations in permeability for carbonate samples with a variety of complex pore structures the analyses however can be done on any thin sections of other rock types the om images provide macroporosity information whereas the esem images yield information on microporosity the boundary between macroporosity and microporosity is defined at a pore area of 500 m2 which translates to a pore length of approximately 20 m which is roughly the thickness of a thin section and thus the resolution of the om the digitized thin section images are binarized into a macropore and a matrix phase om or a micropore and a solid phase esem a standard digital image analysis program is used to detect all individual pores and to measure pore area and pore perimeter based on these analyses one can calculate for each sample the amount of macroporosity the amount of microporosity within the matrix intrinsic microporosity the shapes of the macropores perimeter over area and the pore size distribution comparison of total porosity determined from plugs indicates that macroporosity and microporosity values based on this methodology match the plug data confirming the validity of the method the combination of macroporosity and microporosity data yields pore size distribution and pore shape information that can explain the distribution of physical properties in particular permeability in parameter sensitivity analyses using neural networks permeability appears to be mainly controlled by the macropore shape in high permeability samples and by the amount of intrinsic microporosity in the low permeability samples

calciturbidite dynamics and endobenthic colonisation example from a late barremian early cretaceous succession in southeastern france three lower cretaceous calciturbidite bundles well exposed in the southeastern france are studied with a combined sedimentological and ichnological approach they were deposited in a toe of slope setting in the western border of the vocontian trough during the late barremian the bundles appear to be the result of a cyclic sedimentation with recurrent ichnotaxa including common thalassinoides planolites zoophycos and less abundant taenidium chondrites and ophiomorpha these trace fossils constitute some ichnoassemblages that follow and superimpose each other analysis of the tiering produced may help to estimate the time interval between two turbiditic events indeed the presence of zoophycos indicates a low frequency of the turbiditic supplies which allowed the substrate to firm up a necessary condition for the construction and the persistence of this spreite trace fossil therefore a decreasing frequency of the turbiditic events is pointed out from the base to the top of each turbidite bundle the trace fossil distribution may also be influenced by the grain size in fact zoophycos producers seem to have thrived in a fine grained sediment 0 1 0 2 mm moreover the organic matter exported from the platform is better preserved in these fine grained substrates and may be more available to opportunistic burrowers in the studied succession two different morphologies of zoophycos have been observed one of them lobed form probably indicates an opportunistic behaviour of an organism quickly exploiting the organic matter between two turbiditic events by comparison the other unlobed form is produced later by a more specialised organism exploiting large amounts of organic matter during episodes of lower frequency of turbiditic supplies the ichnofauna studied is characterized by a low diversity and this may be related to an inner submarine fan setting

carbonate apron models alternatives to the submarine fan model for paleoenvironmental analysis and hydrocarbon exploration sediment gravity flow deposition along the deep water flanks of carbonate platforms typically does not produce submarine fans rather wedge shaped carbonate aprons develop parallel to the adjacent shelf slope break the major difference between submarine fans and carbonate aprons is a point source with channelized sedimentation on fans versus a line source with sheet flow sedimentation on aprons two types of carbonate aprons may develop along relatively gentle 4 platform margin slopes aprons form immediately adjacent to the shallow water platform and are referred to as carbonate slope aprons along relatively steep 4 15 platform margin slopes redeposited limestones accumulate in a base of slope setting by passing an upper slope via a multitude of small submarine canyons and are referred to as carbonate base of slope aprons both apron types are further subdivided into inner and outer facies belts inner apron sediments consist of thick mud supported conglomerates and megabreccias facies f as well as thick coarse grained turbidites facies a interbedded with subordinate amounts of fine grained peri platform ooze facies g outer apron sediments consist of thinner grain supported conglomerates and turbidites facies a as well as classical turbidites facies c with recognizable bouma divisions interbedded with approximately equal proportions of peri platform ooze facies g seaward aprons grade laterally into basinal facies of thin base cut out carbonate turbidites facies d that are subordinate to peri platform oozes facies g carbonate base of slope aprons grade shelfward into an upper slope facies of fine grained peri platform ooze facies g cut by numerous small canyons that are filled with coarse debris as well as intraformational truncation surfaces which result from submarine sliding in contrast slope aprons grade shelfward immediately into shoal water platform margin facies without an intervening by pass slope the two carbonate apron models presented here offer alternatives to the submarine fan model for paleoenvironmental analysis and hydrocarbon exploration for mass transported carbonate facies

laboratory experiments and numerical simulation of sediment wave formation by turbidity currents abstract this paper presents the results of laboratory experiments and numerical simulations carried out in order to understand the mechanism of sediment wave formation by turbidity currents experimental turbidity currents were generated in a 10 m long laboratory flume so as to investigate the topographic effects of slope and ridges on turbidite deposition the results indicate that preferential deposition occurs on the upstream side of the ridges this preferential deposition is considered to result in possible upstream migration of the topography a common feature of deep sea sediment waves provided that such deposition were repeated the preferential deposition occurred under a subcritical turbidity current implying that antidune flow conditions 0 844

storm deposits and storm generated coarse carbonate breccias on a pelagic outer shelf south east basin france uppermost jurassic limestones of the south east basin france are organized into four facies associations that were deposited in four distinct zones 1 peritidal lagoonal limestones 2 bioclastic and reefal limestones 3 pelagic lime mudstones 4 lime mudstones calcarenites coarse breccias calcarenite deposits of zone 4 exhibit sedimentary structures that are diagnostic of deposition under wave induced combined flow in subzone 4a both vertical and lateral transitions from lime mudstone calcarenite to breccia indicate in situ brecciation under wave cyclic loading breccias were produced by heterogeneous liquefaction of material previously deposited on the sea floor deposits in subzone 4a record relatively long periods 400 kyr of sedimentation below wave base alternating with periods of deposition under wave induced currents and periods of in situ deformation in this zone storm waves were attenuated by wave sediment interaction and wave energy was absorbed by the deformation of soft sediment with reference to present day wave attenuation water depths in this zone ranged between 50 and 80 m landwards of the attenuation zone in zone 3 storm waves were reduced to fair weather wave heights storm wave base was not horizontal and became shallower landwards as a consequence water depth and wave energy were not linearly related on a small area of the seaward edge of subzone 4a cobbles were removed by traction currents and redeposited in subzone 4b there they formed a 100 m thick wedge which prograded over 3 km and was built up by the stacking of 5 to 20 m thick cross stratified sets of coarse breccia this wedge records the transport and redeposition of cobbles by a high velocity unidirectional component of a combined flow the increase in flow velocity in a restricted area is proposed to result from flow concentration in a channel like structure of the downwelling in the gulf formed by the basin in more distal subzone 4c the hydrodynamic effect of wave induced currents was quasi permanent and brecciation by wave sediment interaction occurred only episodically this indicates that seawards of the attenuation zone hydrodynamic storm wave base was deeper than mechanical storm wave base uppermost jurassic carbonates were deposited and soft sediment deformed on a hurricane dominated ramp of very gentle slope and characterized by a zone of storm wave degeneration located seawards of a zone of sedimentation below wave base

carbonate turbidites in a mesozoic pelagic basin scaglia formation apennines comparison with siliciclastic depositional models abstract in the central apennines during most of the mesozoic a carbonate platform shed detrital material that was discharged by turbidity currents into an adjacent basin a sedimentological study of these detrital bodies has revealed that the depositional fan models largely applied to siliciclastic turbidites are not appropriate for carbonate turbidites the downslope succession of carbonate and siliciclastic facies and deposits are similar in a general way but carbonate turbidites do not appear to be organized into fan bodies apenninic calcarenite turbidites constitute sedimentary bodies 10 20 m thick are elongated more than 40 km along strike and are less than 10 km across such a shape is not consistent either with that of a hemicircular fan or with an ellipsoidal suprafan lobe morphology it suggests instead a kind of submarine piedmont debris sheet or a debris apron the different areal distribution of carbonate turbidites versus siliciclastic ones seems to be caused by a differences in composition scaglia turbidites are very poor in mud and the turbidity currents which had low transport efficiency deposited detritus abruptly at the end of the slope and had no opportunity to disperse sediments over wide areas b differences in feeding system carbonate detritus was not supplied by one large channel but rather from many small channels along the platform margin discrete turbidity currents deposited sediment at the base of the slope producing small deposits that coalesced to form a debris apron and c tectonic control a synsedimentary fault system occasionally rejuvenated the escarpment preventing the development of a large sedimentary body the final morphology was controlled more by tectonics than by sedimentation

a carbonate submarine fan in a fault controlled basin of the upper jurassic betic cordillera southern spain the middle member of the loma del toril formation kimmeridgian lower tithonian intermediate units betic cordillera consists of up to 250 m of resedimented carbonate material three units have been distinguished the lower unit a is composed of conglomerates that are interpreted as deposited in a major valley on the lower slope of a basin margin unit b calcarenites with some conglomerate intercalation is interpreted as distributary channel deposits and unit c calcarenites as the result of poorly developed depositional lobes of a submarine fan the three units form a recessional sequence they cannot be related to a transgression because the kimmeridgian lower tithonian in the prebetic zone where epicontinental sediments exist is clearly regressive the upper member of the loma del toril formation made up of pelagic limestones with sporadic calcarenites or even thin conglomerate intercalations is best interpreted as a basin plain facies lateral facies relationships suggest that down faulting of the basin floor controlled the development of the fan the scarce occurrence of turbidite beds in the basin plain facies the prevailing channelized facies and the obvious lack of overbank deposits suggest a transport system of low efficiency with fan deposition at the base of slope the underlying jurassic strata cropping out along fault scarps coeval carbonate shelf material and upper slope deposits were the main sources of turbiditic resediments with respect to basin morphology sedimentary processes and fan geometry this jurassic turbidite basin can be compared with the modern california continental borderland ancient analogues have been described by reinhart 1977 and price 1977

experimental turbidity currents entering density stratified water analogues for turbidites in mediterranean hypersaline basins experimental turbidity currents entering two layer density stratified water behave differently from similar currents flowing over the same topography into non stratified water experiments were designed as analogues for flows entering mediterranean hypersaline pools in both the hypersaline pools and the experiments the water density changes abruptly across a pycnocline turbidity currents generated on a platform at the level of the pycnocline behaved in one of three ways as they flowed from the platform into deeper stratified water 1 when the bulk density of the current was less than the dense water layer the current spread at the pycnocline the head of the current advanced rapidly when it lost contact with the bed grains settling out of the current fell through the dense water layer forming an extensive deposit in nature this behaviour will lead to turbidites with sharp but non erosive bases strongly developed grading and no traction features 2 when the bulk density of the current was greater than the dense water layer the current continued as an underflow plunging into the deeper water sedimentation lowered the bulk density of the current and the low density interstitial fluid caused the head to loft low density interstitial fluid convected from the body of the current lofting particles into the water column these particles were hydraulically sorted during upward transport and subsequent settling to the floor the resulting turbidites had a more limited extent than the deposits of either non lofting underflows or interflows by inference from the experiments natural deposits of this type may have local proximal erosion and traction features at the base and strongly graded tops 3 in some of the currents with high bulk density the rising turbid water reached the pycnocline and spread at that level as a secondary interflow the tail of the turbidity current which was less dense than the head and body of the current flowed above the pycnocline adding momentum to the secondary interflow the thin non erosive graded deposit from the secondary interflow may extend beyond the deposits of the primary underflow in all three cases but more pronounced in cases 2 and 3 the interaction of the current with the pycnocline displaced that surface and generated a wave that was reflected back and forth from each end of the pool the waves remobilized sediment on the ramp

a carbonate submarine fan sequence from the jurassic of portugal abstract a prograding carbonate submarine fan sequence is described from the toarcian aalenian of western portugal the sequence is predominantly composed of shallow water carbonate grains but can be interpreted using the current siliclastic submarine fan models basin plain to outer fan braided channel midfan and large channel fill sequences can be recognized the source of the carbonate grains was a platform developed on an uplifted hercynian horst to the west of present mainland portugal the fan sequence overlies restricted basin deposits with organic rich mudstones and shales this association of restricted basin facies and a thick over 300 m carbonate grainstone could be an attractive hydrocarbon play however such limestone sequences are easily misinterpreted as in situ shelf carb nates

halokinetic sequences in carbonate systems an example from the middle albian bakio breccias formation basque country spain in diapir flanks unconformity bounded sedimentary packages associated with gravity driven deposits controlled by the ratio between the rates of sediment accumulation and diapir growth can be interpreted in the context of halokinetic sequences the bakio breccias formation basque country spain corresponds to redeposited carbonate deposit that developed in response to the bakio diapir growth during the middle albian these deposits provide on of the rare documented example of carbonate dominated halokinetic sequences the bakio breccias formation consists of an alternation of clast and matrix supported breccias calcirudite calcarenite and marl deposited along the flanks of the diapir the description and the analysis of the bakio breccias formation lead to a new model for carbonate dominated halokinetic sequences these sequences differ from their siliciclastic counterpart because sediment accumulation rate is controlled by carbonate platform growth on the topographic relief top of the diapirs while sediments are preferentially deposited in the mini basins adjacent of the diapirs in siliciclastic settings during transgressive system tract carbonate platform are able to keep up with the sea level rise and to aggrade on top of the diapirs forming thick and resistant roof which is assumed to limit the diapir growth and thus to favour the development of halokinetic sequences with low angle unconformities wedge halokinetic sequences during late highstand system tract deposition and lowstand system tract if present platform progradation results in high sediment accumulation in the adjacent depocenters loading the autochthonous salt layer and promote diapir growth and creation of topographic relief in addition if the diapir roof reaches emersion karstification of the carbonate platform top may also favour roof destruction and diapir growth depending on the thickness of the roof developed previously and the amplitude of the sea level fall the halokinetic sequences with the emersion and the karstification of the carbonate platform may display high angle unconformities hook halokinetic sequences furthermore gravity driven deposits are assumed to be more common in carbonate dominated halokinetic sequences compared to their siliciclastic counterparts since carbonate platform aggradation creates steep slopes on the diapir margins leading to the partial collapse of the margin even when limited diapir growth occurs the carbonate dominated halokinetic sequence model proposed here is an important tool for the prediction of potential reservoir distribution seal and hydrocarbon migration in flanks of salt diapirs where carbonate platform developed

sedimentary patterns and geometries of the bahamian outer carbonate ramp miocene lower pliocene great bahama bank core logging and high resolution seismic data from odp leg 166 were used to analyse deposits of the neogene miocene lower pliocene bahamian outer carbonate ramp ramp sediments are cyclic alternations of light and dark grey wackestones packstones with interbedded calciturbidite packages and minor slumps cyclicity was driven by high frequency sea level changes light grey layers containing shallow water bioclasts were formed when the ramp exported material whereas the dark grey layers are dominantly pelagic calciturbidites are arranged into mounded lobes with feeder channels internal bedding of the lobes shows a north directed shingling as a result of the asymmetrical growth of these bodies calciturbidite packages occur below and above sequence boundaries indicating that turbidite shedding occurred during third order sea level highstands and lowstands highstand turbidites contain shallow water components such as green algal debris and epiphytic foraminifera whereas lowstand turbidites are dominated by abraded bioclastic detritus gravity flow depocentres shifted from an outer ramp position during the early miocene to a basin floor setting during the late miocene to early pliocene this change was triggered by an intensification of the strength of bottom currents during the tortonian which was also responsible for shaping the convex morphology of the outer ramp the miocene and lower pliocene of the leeward flank of great bahama bank provides an example of the poorly known depositional setting of the outer part of distally steepened carbonate ramps the contrast between its sedimentary patterns and the well known upper pliocene quaternary slope facies associations of the flat topped great bahama bank shows the strong control that the morphology of a carbonate platform exerts on the depositional architecture of the adjacent slope and base of slope successions

the effects of topography on sedimentation from particle laden turbulent density currents abstract we present results from a series of laboratory experiments that illustrate the influence of changes in channel topography depth or width on the sedimentation patterns produced by steady particle laden currents on a planar surface in a channel with constant width such currents created deposits that thinned exponentially with distance as long as a current was not blocked to produce a bore topographic features consisting of constrictions ridges and sudden openings caused no significant deviation from exponential deposit thinning or discontinuity in thickness even when there was a transition in flow regime caused by the topographic feature changes in the channel width did affect the distance over which the deposit thinned with the deposits associated with wider parts of the channel thinning more rapidly with distance in contrast if the topographic change was large enough to partially reflect the flow producing an upstream propagating bore then the deposit did not thin exponentially the results are consistent with a model in which the current is assumed to be turbulent and well mixed in this case sedimentation occurs at a rate proportional to the channel width the settling speed of the particles and their concentration within the current and inversely proportional to the current discharge such a model predicts that as a flow passes through a topographic control that does not produce a bore the deposit continues to thin exponentially even if the flow undergoes a transition from the subcritical to the supercritical regime the results suggest that in natural systems changes in current speed and flow regime do not in themselves produce changes in deposit thickness or gradient in thickness unless the flow is partially blocked and a fraction of the flow is reflected upstream

porosity gain and loss in unconventional reservoirs example of rock typing in lower cretaceous hemipelagic limestones se france provence abstract we characterize porosity evolution in hemipelagic limestones of the lower cretaceous vocontian basin northern provence se france which are surface analogs for deep unconventional reservoirs firstly a structural and sedimentologic analysis was conducted on outcrops and on borehole cores of berriasian to lower valanginian rocks secondly 330 plugs were analyzed for facies pore typing porosity and acoustic vp velocity measurements this petrophysical dataset was compared to the burial uplift history of the host rock hemipelagic carbonates include four sedimentary formations comprising nine facies splitted into mud and grain dominated formations which display 0 8 porosity range depending on the initial grain to mud ratio of the sediments and on basin stress regime evolution during burial uplift history initial porosity was better preserved in grain dominated formations where early micritic cements built bridges between grains generating a solid skeleton that prevented inhibited the burial compaction effects in mud dominated facies micrite was initially diffuse within the rock matrix but was progressively rearranged under burial stress while the generation of an extensive amount of stylolites occurred the differential response of compacted grain and mud dominated facies to a late regional 1 km uplift resulted in large porosity generation should range from 15 to 35 localized in the mud dominated facies through the dilatancy of stylolite and pressure solution seams this study highlights how important is the combination of classical approaches including facies pore type and diagenesis characterization with the structural analyses one key result applicable to several types of unconventional reservoirs is the effective porosity generated by reactivation of compaction structures

submarine lobes and feeder channels of redeposited temperate carbonate and mixed siliciclastic carbonate platform deposits vera basin almeria southern spain temperate carbonates and mixed siliciclastics carbonates of upper tortonian age were deposited on a narrow platform along the southeastern margin of the sierra de los filabres on the western side of the vera basin the temperate carbonates were unlithified or were only weakly lithified on the seafloor and so were easily prone to synsedimentary removal part of the shelf sediments were eroded reworked and redeposited in submarine lobes up to 40 m thick and 1 km wide the lobes consist of turbiditic carbonates calcarenites and calcirudites and mixed siliciclastics carbonates which contain up to 30 siliciclasts derived from the sierra de los filabres to the northwest and abundant bioclasts of coralline algae bivalves and bryozoans in the inner platform the feeder channels of the lobes cross cut beach and shoal deposits and are filled by strings of debris flow conglomerates up to 3 m thick and a few metres wide these channels presumably developed as the continuation of river courses entering the sea further towards the outer platform they pass into large channels up to several hundred metres wide and 20 m deep steeply cutting into the horizontally bedded strata of the platform significant quantities of platform sediment were removed by erosion during their excavation once abandoned they were filled by new platform sediments further towards the basin the channels associated with the lobes exhibit lateral accretion and internal cut and fill structures and are intercalated between hemipelagic deposits the channel filling sediments are in this latter case coarse grained carbonates and mixed siliciclastics carbonates lobe development concentrated first at cortijo grande on the western side of the

detailed anatomy of a deep water carbonate breccia lobe upper jurassic french subalpine basin abstract detailed correlations across tithonian carbonate breccia deposits in the drome river area northern part of the so called vocontian through suggest the depositional system was that of an elongated deep water lobe up to 70 km long and 20 to 30 km wide for a thickness reaching 200 m the drome lobe as it is now called is mainly made of slope to basinal mudstones breccias with minor platform components interpreted as debris flow and mud flow deposits associated with slump deposits it is basically a base of slope system whose elongated depositional area implies it was a point sourced gravity system thus perhaps connected to a small canyon cut onto the western slope of the basin but the mostly mudstone material of the breccias also suggests that the walls of this inferred canyon were the main supplier of the lobe not the carbonate platform proper the updip part of the lobe has a complex internal geometry as the deposition of breccia bed packages is interrupted by scourings locally 50 m deep indicating maybe a canyon mouth environment the middle part of the lobe is dominated by pure vertical aggradation of breccia beds with minor intervening erosion in the downdip part of the system a morphological compensation mechanism occurs as breccia beds tend to spread laterally a huge slump carrying large mudstone olistoliths ends the breccia deposition at the beginning of the berriasian this megaslump deposit was mostly emplaced on the right side of the breccia lobe supporting the idea of a depositional relief our observations thus show that previous interpretations as a submarine canyon infilling or as shallow water breccias formed in situ by cyclic loading under attenuating hurricane waves approaching the platform are not consistent with our observations the internal geometry of the system studied brings new data about a poorly studied kind of turbidite systems that of deep water carbonate breccias

shelf to basin resedimented carbonates of the southern margin of the jurassic central high atlas trough morocco abstract the central high atlas mountains occupy the site of an early to middle jurassic east west trending seaway known as the central high atlas trough late triassic early jurassic continental rifting combined with a transtensional structural regime formed a system of pull apart basins comprising the trough a thick sequence of carbonate shelf to basin plain deposits filled the trough and were later uplifted and exposed during the oligocene alpine orogeny stratigraphic analysis of 50 km sup 2 located along the trough s southern shelf margin reveals a 1 200 m thick wedge of slope and basin plain deposits these deposits are divided into four lithostratigraphic units 1 pelagic mudstones 2 channel deposits composed of grainstones and packstones interbedded with marls and mudstones 3 turbidite deposits composed of grainstones packstones and wackestones cyclically interbedded with marls and mudstones and 4 cyclically interbedded marls and mudstones this laterally continuous thick wedge of resedimented deposits suggests that a line source of platform margin sediments fed coalescing base of slope aprons these aprons probably accumulated in an actively subsiding half graben parallel to the shelf margin while tectonics played the major role in basin evolution sea level fluctuations and climate influenced the influx of carbonate and terrigenous sediments rapid cessation of mid sinemurian shallow water platform deposition and regionally transgressive domerian toarcianmore marls indicate eustatic sea level rises affected basin sedimentation periodic climate changes perhaps related to the milankovitch effect may have led to systematic variations in carbonate sediment supply resulting in cyclic sedimentation less

architecture and evolution of calciclastic marginal slope fans of the ordovician carbonate platform in the yijianfang outcrop of the bachu area west tarim basin the ordovician carbonate platform at the yijianfang outcrop of the bachu uplift region in the western tarim basin contains four types of genetic facies associations developed in the calciclastic slope fan depositional system an olistostrome zone fan channels lobes and a marginal slope the olistostrome zone is characterized by olistoliths and slump fans whereas the fan channels and lobes are further divided into proximal and distal facies the marginal slope deposits constitute the background sedimentation in which the calciclastic slope fans are intercalated from proximal to distal parts of the fan channels and lobes their scale gradually becomes smaller and the size and sorting of grains become finer and better respectively analysis of the stratigraphic framework indicates that the fans formed in the lower strata of the upper ordovician lianglitage formation in four high frequency sequences i e pss1 pss4 field paleocurrent measurements indicate northeast southwest depositional strike for the early platform margin of the lianglitage formation sediments in the calciclastic slope fans were derived from the platform margin and evolution of the calciclastic slope fans was generally progradational from pss1 to pss2 and then continuously retrogradational from pss2 to pss4 the calciclastic slope fans in the outcrop area are not reservoir prone rocks but interpretation on these fans can provide useful information about potential hydrocarbon reservoirs along the platform margin the p wave velocity s wave velocity and density variations in each genetic facies may be used to identify the subsurface calciclastic slope fan depositional system

carbonate turbidite sequences deposited in rift basins of the jurassic tethys ocean eastern alps switzerland syn rift sediments in basins formed along the future southern continental margin of the jurassic tethys ocean comprise in the eastern alps of switzerland up to 500 m thick carbonate turbidite sequences interbedded with bioturbated marls and limestones in the fault bounded troughs no submarine fans developed in contrast the fault scarps acted as a line source and the asymmetric geometry as well as the evolution of the basin determined the distribution of redeposited carbonates the most abundant redeposits are bio and lithoclastic grainstones and packstones with sedimentary structures indicating a wide range of transport mechanisms from grain flow to high and low density turbidity currents huge chaotic megabreccias record catastrophic depositional events their main detrital components are upper triassic shallow water carbonates and skeletal debris from nearby submarine highs after an event of extensional tectonism sedimentary prisms accumulated in the basins along the faults each prism is wedge shaped with a horizontal upper boundary and consists of a thinning and fining upward megacycle within each megacycle six facies associations are distinguished at the base of the fault scarp an association of breccias was first deposited by submarine rockfall and rockfall avalanches a narrow approximately 4000 m wide depression along the fault was subsequently filled by the megabreccia association in which huge megabreccias interfinger with thin bedded turbidites and hemipelagic limestones the thick bedded turbidite association covered the megabreccias or formed farther basinward the base of the sedimentary column within the thick bedded turbidites thinning and fining upward cycles are common the overlying thin bedded turbidite association shows nearly no cyclicity and the monotonous sequence of fine grained calciturbidites covers most of the basin area with continuous filling and diminishing sediment supply a basin plain association developed comprising fine grained and thin bedded turbidites intercalated with bioturbated marls and limestones on the gentle slopes opposite the fault escarpment redeposited beds are scarce and marl limestone alternations as well as weakly nodular limestones prevail

the gothara plagiogranite evidence for oceanic magmatism in a non ophiolitic association north khetri copper belt rajasthan india abstract the gothara granitoid a small pluton in the vicinity of khetri town is one of several granitoid bodies that intrude the palaeo mesoproterozoic delhi supergroup of the khetri copper belt kcb in north rajasthan india detailed petrological and geochemical investigations characterise the gothara granitoid as a plagiogranite it exhibits profuse granophyric intergrowth between quartz and chessboard albite besides having the low al2o3 extremely low k2o rb ba and high na2o that are characteristic of plagiogranites and matches some typical oceanic plagiogranites of the world in totality however unlike the other known plagiogranites it is mineralogically and chemically exceptionally homogeneous almost free from alteration and occurs in a non ophiolitic setting the field relationships of the gothara plagiogranite particularly its dual and overlapping relationship with the mafic magmatic rocks its accessory mineral assemblage i type characteristics and the major trace and ree geochemistry all point towards its fractionation related petrogenesis from a mafic magma of mantle origin in an oceanic ridge tectonic regime this discovery is of importance not only for the petrotectonic evolution of the khetri copper belt but also for the petrogenesis of plagiogranites elsewhere in the world

the base of slope carbonate breccia system of ceuse tithonian s e france occurrence of progradational stratification in the head plug of coarse granular flow deposits abstract once interpreted as a deep water canyon infilling and later as some kind of tempestite deposit the tithonian breccias of ceuse are here reinterpreted as a small lobe deposit emplaced at the mouth of a gully cutting into a slope between two deep water terraces in the eastern part of the subalpine basin the breccias belong to two basic categories mostly grain supported and occasionally mud supported spectacular large scale oblique geometries apparent lateral accretions are observed in the grain supported breccias both within the infilling of the lower feeder channel and in the updip part of the lobe detailed analyses of these geometries show that they correspond to progradational features both laterally and in a more distal position on the lobe these progradational bodies evolve into a pile of unsorted massive breccias sometimes showing a crude even stratification we thus propose a depositional model for the grain supported breccias linking the two facies as follows the deposition of a gravity flow begins at the toe of slope mouth of the tributary gully by a progradational head which evolves downslope and laterally to a splay of massive or crudely stratified breccia the internal oblique stratification flattens distally over a distance of a few kilometres elementary beds pile up in morphological compensation to build the 100 m thick breccia body of ceuse because the breccias are derived from the gravity reworking of deep water nodular carbonates there is no sand sized material available in the depositional system or only a little probably produced through an erosive clast grain diminution process during transport this explains why the thick breccia beds pass quickly eastward to thin bedded mud turbidites

triassic carbonate submarine fans along the arabian platform margin sumeini group oman the sumeini group formed along the passive continental margin slope that bounded the northeastern edge of the arabian carbonate platform with the initial development of this passive continental margin in oman during early to middle triassic time possibly permian small carbonate submarine fans of the c member of the maqam formation developed along a distally steepened slope the fan deposits occur as several discrete lenticular sequences of genetically related beds of coarsegrained redeposited carbonate calciclastic sediment within a thick interval of basinal lime mudstone and shale repeated pulses of calciclastic sediment were derived from ooid shoals on an adjacent carbonate platform and contain coarser intraclasts eroded from the surrounding slope deposits sediment gravity flows primarily turbidites with lesser debris flows and grain flows transported the coarse sediments to the relatively deep submarine fans channel erosion was a major source of intraformational calcirudite two small submarine fan systems were each recurrently supplied with calciclastic sediment derived from point sources submarine canyons the northern fan system retrogrades and dies out upsection the southern fan system was apparently longer lived calciclastic sediments in it are more prevalent and occur throughout the section the proximal portions of this fan system are dominated by channelized beds of calcirudite which represent inner to mid fan channel complexes the distal portions include mostly lenticular unchannelized beds of calcarenite apparently mid to outer fan lobes carbonate submarine fans appear to be rare in the geological record in comparison with more laterally continuous slope aprons of coarse redeposited sediment the carbonate submarine fans of the c member apparently formed by the funnelling of coarse calciclastic sediment into small submarine canyons which may have developed due to rift and or transform tectonics the alternation of discrete sequences of calciclastic sediment with thick intervals of background sediment resulted from either sea level fluctuations or pulses of tectonic activity

geometry and petrophysical parameters of a calcarenitic turbidite lobe barremian aptian pas de la cluse france abstract several bioclastic resedimentation systems late barremian to early aptian in age outcrop in southeastern france the upslope portion of a calcarenitic turbidite lobe outcrops as a cliff 2 3 km wide and up to 45 m high oriented roughly perpendicular to the direction of palaeoflow it has been studied through 31 sections the studied body is point sourced and corresponds to a channel lobe transition located at the toe of slope of a urgonian carbonate platform on the western edge of the vocontian trough french subalpine chains the internal geometry of the lobe is the result of repeated erosion and filling of channels creating well defined stacked units filling phases result in lobe shaped morphology units evolve from base to top in an ordered way first the sediments exported from the platform and deposited in the basin are represented by decimetre thick sheet like and fine grained bouma a e and ab e sequences in this first unit erosion is limited and represented by shallow and symmetrical channels this initial phase of deposition corresponds to the formation of a lobe with a positive morphology the next phase of system development is more erosional and this is dominated by migrating sinuous channels several metres deep filled with coarse grained poorly graded turbidites these channels are first filled through lateral accretion and then sediment spills over to create a sub lobe the mixture of channel and lobe features could be considered as a carbonate equivalent of the channel levee system of siliciclastic deposits finally the system ends with the deposition of a flat based unit this unit extends for more than 2 km and is composed of the southwards lateral accretion of hundreds of metres wide sequences each composed of a debris flow deposit capped by a coarse grained calcarenite bed these sigmoidal bodies could be the ultimate forms of a spreading out phenomenon of the lobe overall the pas de la cluse system is a coarsening upward body as the grain size is related to the nature of the material this coarsening upward implies either an evolution in the nature of the carbonate material produced on the platform from grainy to bioconstructed a displacement of the source sediment from inner platform to margin or a displacement of the channel head through time from distal to proximal the upward evolution from classic turbidites to debris flow deposits can be explained either by the way the platform facies evolved with time in a depositional sequence or through retrogressive erosion by successive slope failures that cut deeper and deeper into the platform slope although its present day porosity is low the size of the system and the fact that it is encased in marls make it an interesting outcrop analogue for hydrocarbon exploration

progradational patterns at the head of single units of base of slope submarine granular flow deposits conglomerats des gâs coniacian se france upper cretaceous conglomerates sandstones and calcarenites outcropping in the glandage syncline les gas gorge belong to two superimposed turbidite systems the first being the shortest about two hundred metres thick five kilometres wide and a mere ten kilometres long both onlap a sw ne oriented palaeoslope created by faulting in the latest turonian on the southern edge of the vercors carbonate platform the first system is coniacian in age the second probably campanian this study deals only with the first system which comprises in stratigraphic order classical sandstone turbidites clast supported conglomerates and coarse grained cross bedded sandy calcarenites the transition between the last two lithologies is progressive allowing the mechanisms responsible for apparent lateral accretions found pervasively in both the conglomerates and the calcarenites to be understood here cross bedding is not the result of changes in the direction of accretion in lateral bars or in oblique infillings of sinuous channels as is often suggested in other similar deep water carbonate systems each event bed comprises a prograding conglomeratic head plug blanketed in continuous sedimentation by forward spreading bioclastic calcarenites the superimposition of such mixed beds gives rise to a low angle cross stratification an unusual feature for a system interpreted as a base of slope apron conglomerates were probably deposited through a granular flow mechanism at a strong hydraulic jump at the base of the slope associated calcarenites show supercritical flow features the undulating transverse architecture of its large head onlapping the paleoslope suggests it is a multi apex apron the sandstone conglomerate calcarenite succession of the depositional sequence is interpreted as overall transgressive after the late turonian tectonic phase that led to the exposure of the vercors carbonate platform updip

chert occurrences in carbonate turbidites examples from the upper jurassic of the betic mountains southern spain in upper jurassic carbonate turbidites of the betic mountains southern spain chert occurs in three morphologies bedded chert nodular chert and mottled chert the last refers to a weak dispersed and selective silification which gives a speckled appearance to the rock the three types of chert are formed by replacement of limestones and are associated with different calcareous facies turbidite packstones of saccocoma and peloids and turbidite lime mudstones of pelagic material contain bedded and nodular cherts the silicification textures are mainly micro and cryptocrystalline quartz with local chalcedonic quartz both length fast and length slow which is more common in the packstones only mottled chert is produced where calcareous breccia beds are silicified mottled chert consists of micro and cryptocrystalline quartz length slow chalcedonic quartz and mosaics or individual crystals of euhedral megaquartz beds and nodules are the result of early diagenetic silicification with silica derived from the calcitization and dissolution of radiolarians and subordinately sponge spicules whereas mottled chert is the consequence of later silicification in a probably mg rich environment early silicification is mainly confined to turbidite beds and only rarely occurs in the interbedded pelagic limestones turbidite sedimentation favours silicification because rapid burial of the transported siliceous tests prevents silica from the dissolution of tests passing into overlying sea water a silica rich interstitial fluid develops in the turbidite layer and this migrates to more permeable zones giving rise to bedded and nodular chert

why the phosphorus retention of lakes does not necessarily depend on the oxygen supply to their sediment surface in order to improve the trophic state of lake sempach a eutrophied lake in central switzerland its external phosphorus p load has been decreased and its hypolimnion has been artificially oxygenated to lower the lake internal p recycling based on more than 15 yr of experience we conclude that the reduction of the external p load resulted in a corresponding decrease of the lake s p concentration however contrary to initial expectations increased hypolimnetic dissolved oxygen concentrations neither 1 reduced the p release from sediments during summer nor 2 resulted in an increased permanent p retention these observations warrant a reevaluation of the well accepted management strategy of decreasing the lake internal p cycling by maintaining an aerobic hypolimnion and sediment surface we hypothesize that oxygenation only results in an increased permanent benthic p burial if because of the depressed sulfide production more ferrous phosphate e g vivianite and less fes is deposited in the anoxic sediment hence it is not the oxic sediment surface that directly affects the permanent redox dependent sediment p retention but the molar ratio of the available reactive fe ii s 2 po 4 in the anoxic sediment this ratio is driven by the settling rate and the nature of organic matter and particulate iron as well as the supply of oxygen nitrate and sulfate to the sediment