slope apron deposition in an ordovician arc related setting the vuelta de las tolas member suri formation famatina basin northwest argentina abstract the ordovician suri formation is part of the infill of the famatina basin of northwest argentina which formed in an active setting along the western margin of early paleozoic gondwana the lower part of this formation the vuelta de las tolas member records sedimentation on a slope apron formed in an intra arc basin situated on a flooded continental arc platform the coincidence of a thick arenig llanvirn sedimentary succession and volcanic plutonic arc rocks suggests an extensional or transtensional arc setting and is consistent with evidence of an extensional regime within the volcanic are in the northern puna region the studied stratigraphic sections consist of volcanic rocks and six sedimentary facies the facies can be clustered into four facies associations association 1 composed of facies a laminated siltstones and mudstones and b massive mudstones and siltstones is interpreted to have accumulated from silty muddy high and low density turbidity currents and highly fluid silty debris flows with subsequent reworking by bottom currents and to a lesser extent hemipelagic suspension in an open slope setting facies association 2 is dominated by facies c current rippled siltstones strata these deposits are interpreted to record overbank sedimentation from fine grained turbidity currents facies e matrix supported volcanic breccias interbedded with andesitic lava units comprises facies association 3 deposition was contemporaneous with subaqueous volcanic activity and accumulated from cohesive debris flows in a coarse grained wedge at the base of slope facies association 4 is typified by facies d vitric fine grained sandstones and siltstones and f channelized and graded volcanic conglomerates and breccias deposits these strata commonly display thinning and fining upward trends indicating sedimentation from highly concentrated volcaniclastic turbidity currents in a channelized system the general characteristics of these deposits of fresh pyroclastic detritus suggest that their accumulation was contemporaneous with or post dated shallow water or subaereal explosive volcanism the vuelta de las tolas member tends to show an overall random facies patterns reflecting the strong influence of non cyclical episodic processes related to arc volcanism and slope sedimentation the scarcity of resident ichnofaunas and the presence of thick packages of uniform mudstones suggest deposition under oxygen depleted conditions in a topographically confined ponded sub basin interbasinal correlations favor comparison with middle arenig slope apron successions formed in the northern puna basin and suggest a southward prolongation of the arenig volcanic arc

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

core based evidence for sandy slump and sandy debris flow facies in the pliocene and pleistocene of the gulf of mexico implications for submarine fan models examination of nearly 3 500 feet of conventional core from pliocene and pleistocene deep water reservoirs cored in 25 wells in 8 different areas covering the eastern central and western gulf of mexico reveals that the reservoirs are predominantly composed of mass transport deposits mainly sandy slumps and sandy debris flows 60 100 of cored intervals bottom current reworked sands are common 10 50 of importance to existing submarine fan models is that turbidities are extremely rare 1 of all cores sedimentary features indicative of slump and debris flow origin include sand units with sharp upper contacts slump folds discordant steeply dipping layers up to 60 degrees glide planes shear zones brecciated clasts rafted mudstone clasts planar clast fabric inverse grading of clasts and moderate to high matrix content 5 20 these reservoirs have been interpreted by others to represent turbidite dominated basin floor fans and slope fans of the often used sequence stratigraphic model however our core data do not show a dominance of turbidities sandy debris flows exhibit a variety of log motifs e g blocky fining up and coarsening up due to changes in concentration of midstone clasts and a variety of internal seismic facies e g parallel continuous irregular discontinuous chaotic discontinuous and lateral pinch out perhaps due to changes in stacking patternsmore of debris flows and slumps classic submarine fan models commonly advocated for these reservoirs may not be appropriate we propose a slump and debris flow dominated slope model in which sea floor topography and depositional freezing i e plastic flows control sand distribution and geometry contrary to popular belief sandy debris flows can be thick areally extensive and excellent reservoirs less

mass transport processes on amazon cone western equatorial atlantic three large mass transport deposits occur on the upper to middle amazon cone these slump debris flow complexes have been mapped from 3 5 khz echograms and cover approximately 75 000 sq km or about 10 of the cone the debris flows traveled down slopes with gradients as low as 1 90 to 1 165 0 3 to 0 6 for distances up to 300 km these deposits average 10 to 50 m in thickness and the total amount of sediments displaced may exceed 3 800 cu km the upslope parts of these complexes generally consist of hummocky slump or slide deposits which are commonly bounded by scarps of varying relief downslope from this zone of removal the deposits consist of thin the occurrence of such widespread mass movements on the amazon cone indicates that mass transport is probably an important sedimentation process on deep sea fans however most studies and models of modern deep sea fans have minimized or ignored the potential importance of mass transport processes in fan development we suggest that in the future both ancient and modern deep sea fans be more closely examined for mass transport deposits so that the importance of this process to overall fan development can be more accurately assessed

submarine fan and slope apron deposition in a cretaceous forearc basin the gursoku formation kavak samsun n turkey abstract the late cretaceous gursoku formation represents the proximal fill of the sinop samsun forearc basin that was probably initiated by extension during the early cretaceous the succession records sedimentation in two contrasting depositional systems a slope apron flanking a faulted basin margin and coarse grained submarine fans the slope apron deposits consist of thinly bedded turbiditic sandstones and mudstones interbedded with non channelized chaotic boulder beds and intraformational slump sheets representing a spectrum of processes ranging from debris flow to submarine slides the submarine fan sediments are represented by conglomerates and sandstones interpreted as deposited from high density turbidity currents and non cohesive debris flows the occurrence of both slope apron and submarine fan depositional systems in the gursoku formation may indicates that the region was a tectonically active basin margin during the late cretaceous

bed geometry used to test recognition criteria of turbidites and sandy debrites the origin of thick bedded deep water sandstones has generated much controversy in recent years two fundamentally different models have been proposed for beds with the same internal sedimentary characteristics 1 progressive particle settling from the base of a turbulent flow the turbidity current model and 2 en masse freezing of a higher concentration flow the sandy debris flow model these models predict beds with very different geometries turbidites thin gradually whereas debrites have abrupt terminations previous studies have relied upon sedimentary recognition criteria i e sedimentary features in small scale outcrop or core to interpret depositional mechanism in this study depositional mechanism is deduced from bed geometry gained from extensive correlations of individual sandstones preserved in a classic turbidite system marnoso arenacea formation italy this approach allows recognition criteria for turbidites and submarine debrites to be independently tested we find that tabular and tapered sandstones turbidites have distinctly different internal characteristics to beds with abrupt margins debrites turbidites are relatively well sorted often exhibit grading and traction structures and have relatively low matrix mud contents they may also contain massive division floating clasts and inverse grading debrites are moderate to poorly sorted ungraded structureless contain floating clasts and have elevated matrix mud contents these findings have implications for the assessment of submarine gravity flows deposits and reservoir rock characterization

the bouma division a and the possible duration of turbidity currents abstract experimental data arnott and hand 1989 combined with theoretical arguments suggest that the transition in a turbidite from division a to division b occurs at a deposition rate of unsupported grains of about 6 7 10 4 m s 1 in the case of fine medium quartz sand a second rate may be calculated from properties measured at the transition from division b to division c allen 1971b these rates together permit an estimate to be made of the order of magnitude of the duration of deposition from a turbidity current the calculated order of a few tens of minutes for a mio pliocene turbidite described and interpreted hydraulically by komar 1985 is in broad agreement with his independent estimate based on the sequenc of sedimentary structures

interpretation of channelized architecture using three dimensional photo real models pennsylvanian deep water deposits at big rock quarry arkansas abstract mapping geological details and interpreting three dimensional geometries in a highly heterogeneous outcrop such as the exposure at big rock quarry has been a continuous challenge especially because high vertical cliffs make access to most of the rocks difficult for direct geological observations previous interpretations of facies architecture were derived from gamma ray profiles a core and measurements made on two dimensional photomosaics this paper represents the first attempt of three dimensional interpretation of the geometry and facies pattern of the jackfork nested channel complex deposited at the base of slope examination of the photo real model of the outcrop with assigned lithologies allowed extraction of accurate 3 d qualitative as well as quantitative channel dimensions geometric information this facilitated interpretation and reconstruction of the submarine channel complex architecture making possible correlations of strata exposed on the two sides of the quarry most of the exposed vertically and laterally stacked channels are large aggradational with well defined axial regions overlain by matrix supported breccia which grades upward into amalgamated sandstones the thickness of the sandstone decreases toward the southeastern end of the quarry where more shale is present the channel infill consists of thin bedded sandstones interlayered with shale which overlain the breccia the upper part of the quarry is made up of smaller lateral migrating channels significant channel width and thickness variation can be recognized at outcrop scale thirty eight identified channels are characterized by a relatively low aspect ratio 4 1 to 32 1 with channel dimensions ranging from 25 m to 314 m wide and 2 m 24 m deep bed thickness distributions of various facies show that the sandstone comprises a significant proportion 83 of the total channel thickness while shale and breccia represent about 8 and 17 respectively this yields a high net to gross ratio of more than 80 compared to previous reconstructions our 3 d photo real model is more accurate and it can be used to calibrate simulation of processes in deep water environments

deep lacustrine sandy debrites and turbidites in the lower triassic yanchang formation southeast ordos basin central china facies distribution and reservoir quality abstract the deep lacustrine gravity flow deposits are widely developed in the lower triassic yanchang formation southeast ordos basin central china three lithofacies include massive fine grained sandstone banded sandstone and massive oil shale and mudstone the massive fine grained sandstones have sharp upper contacts mud clasts boxed shaped gamma ray gr log but no grading and bouma sequences in contrast the banded sandstones display different bedding characteristics gradational upper contacts and fine upward the massive fine grained sandstones recognized in this study are sandy debrites deposited by sandy debris flows while the banded sandstones are turbidites deposited by turbidity currents not bottom currents the sediment source for these deep gravity flow sediments is a sand rich delta system prograding at the basin margin fabric of the debrites in the sandy debris fields indicates initial formation from slope failure caused by the tectonic movement as the sandy debris flows became diluted by water and clay they became turbidity currents the deep lacustrine depositional model is different from the traditional marine fan or turbidite fan models there are no channels or wide lobate sand bodies in the lower triassic yanchang formation layers within the sandy debrites have higher porosity 8 14 and permeability 0 1 4 md than the turbidites with lower porosity 3 8 and permeability 0 04 1 md consequently only the sandy debrites constitute potential petroleum reservoir intervals results of this study may serve as a model for hydrocarbon exploration and production for deep lacustrine reservoirs from gravity flow systems in similar lacustrine depositional environments

structural profiles of ouachita mountains western arkansas the ouachita mountains of oklahoma and arkansas are the largest exposure of the pennsylvanian age orogen rimming the southern margin of north america the exposure consists of a thick carboniferous flysch sequence overlying a thin early paleozoic deep water sequence and is generally interpreted to have been deformed in a south dipping subduction zone two balanced cross sections 40 km apart of the ouachita mountains in western arkansas are presented here illustrating the regional structural style major features of the cross sections include from north to south 1 triangle zones along the northern border of the frontal thrust zone produced by imbrication at depth 2 large scale 10 km wavelength fault propagation folds in the frontal thrust zone formed prima ily above normal faults that offset the basement and act as buttresses at depth 3 a late stage basement uplift along the reactivated johns valley normal fault system resulting in the antiformal structure of the benton uplift and backthrusts in the northern benton uplift and 4 small scale 1 3 km heavily faulted folds in the early paleozoic deep water rocks exposed in the benton uplift greenschist metamorphism in these rocks is attributed to the estimated 13 km of carboniferous overburden which was later eroded reconstructions of the late paleozoic continental margin are made from the two cross sections the reconstructed shelf to slope transition is interpreted to underlie the southern flank of the benton uplift using modern analogs for the across strike width of the shelf to slope transition a minimum regional shortening estimate of 30 50 110 155 km is obtained for deep water rocks currently exposed in the benton uplift

a preliminary experimental study of turbidite fan deposits discussion parsons et al 2002 have discussed an experimental study of turbidite fan deposits for understanding lobe switching because of the perceived importance of turbidite lobes in hydrocarbon reservoirs shanmugam and moiola 1991 this experimental study could be of value to the oil industry also experimental studies are the primary means of unraveling the complexities of the process dynamics of turbidity currents and their deposits this is because the other two options namely 1 direct observations of turbidity currents in the deep sea e g shepard et al 1979 and 2 attempts to understand turbidity currents and their fan deposits on the basis of outcrop study on land e g mutti and ricci lucchi 1972 have proven to be unsuccessful e g mutti 1992 shanmugam 2002 therefore the experimental study by parsons et al 2002 requires close scrutiny i would like to debate the following issues discussed in the paper 1 reynolds number 2 grain size variation 3 depositional bedforms and 4 importance of mud proper scaling of experimental flows to natural turbidity currents is vital according to parsons et al 2002 p 626 the reynolds number of bottom boundary layer in natural turbidity currents is often greater than 100 whereas the reynolds number of experimental turbidity currents was always much less than unity parsons et al 2002 p 626 also acknowledged that the particle reynolds number in these experiments is not compatible with values of natural flows the authors attributed these scaling difficulties to the density of the particles and the viscosity of the fluid used in their

multidirectional synchronously triggered seismo turbidites and debrites revealed by x ray computed tomography ct on 21 april 2007 a mw 6 2 earthquake struck aysen fjord chilean patagonia and caused onshore and offshore mass movements which triggered tsunamis and density flows in the fjord to better understand the facies successions in and the intercalation of the density flow deposits a study was made of the 2007 deposits in 22 short sediment cores taken in the inner aysen fjord by combining grain size analysis with x ray computed tomography scanning it was possible to demonstrate that the encountered facies correspond to classical divisions of debrites and turbidites the single event deposits consist of a succession of several sub deposits deposited under different flow directions and can be interpreted as stacked turbidites orientations of i folds ii imbricated mud clasts iii backsets and foresets of climbing ripples and iv asymmetrical convolute lamination were used to determine relative flow directions at the location of the cores by assigning the basal flow of the stacked debrites and turbidites to the closest principal mass flow the absolute flow directions of the sub deposits were determined which in combination with multibeam basin floor morphology allowed reconstruction of the 2007 density flow successions in aysen fjord furthermore alternating flow directions provide evidence for a seiche induced by the density flows it was concluded that x ray computed tomography scans provide crucial information for reconstructing palaeoflows and can be a useful tool in marine and lacustrine sedimentology and palaeoseismology the multidirectionality of sub deposits in turbidites is next to differences in mineralogy a new criterion to identify stacked turbidites these multidirectional stacked turbidites are an indication of simultaneous triggering of density flows and can therefore in most cases be attributed to earthquakes ruling out other triggers such as floods storms or other sediment failures this article is protected by copyright all rights reserved

slope turbidite packets in a fore arc basin fill sequence of the plio pleistocene kakegawa group their formation and sea level changes discussion

comparison of depositional elements of an ancient and a modern submarine fan complex early pennsylvanian jackfork and late pleistocene mississippi fans normark urged that all future meaningful deep sea fan comparisons be confined to key depositional elements common to most turbidite systems these elements should include basin size tectonic and eustatic setting and depositional process indicators a test case for elemental comparisons between two widely studied fan complexes is presented and evaluated the lower pennsylvanian morrowan jackfork submarine fan complex extends from central arkansas to northeast texas sequence analysis suggests that the jackfork is composed of four to seven depositional episodes and occupies the floor of a deep basin bordered to the north and east by a passive carbonate siliciclastic shelf margin and to the south and east by a northward advancing orogenic belt the jackfork apparently unrestricted to the west and southwest the mississippi submarine fan complex extends from the submerged continental shelf of southern louisiana to the abyssal depths between yucatan and florida the fan complex is primarily pleistocene in age with the present morphologic fan being late wisconsinian the mississippi fan is composed of 17 depositional episodes it occupies the floor of a deep basin bordered on the north and west by quiescent halokinetic siliciclastic shelf margins and to the east and south by passive carbonate margins elemental comparisons between themore mississippi fan and a palynspastically restored jackfork fan complex suggest that both are quite similar even though the mississippi fan is up to three times larger in some categories comparative study of key depositional elements facilities a more complete understanding of both modern and ancient submarine fans less

a preliminary experimental study of turbidite fan deposits we present preliminary laboratory experimental results that demonstrate lobe switching in a turbidite fan after a significant number of individual event beds more than eight in both experimental fans made in this study the flow began to focus itself into a lobe at the center of which appeared a subtle channel form initial lobe switching occurred after nearly twenty event beds subsequent switching appeared to scale with lobe size and sedimentation rate the densest coarsest runs tended to initiate the switching of the depocenter instabilities within the turbidity current itself appear to be responsible for initial flow confinement to a lobe and ultimate switching events currently untreated scale effects and measurement difficulties limit quantitative extension of the results to natural settings though some general relationships are proposed

mixed sand mud bedforms produced by transient turbulent flows in the fringe of submarine fans indicators of flow transformation the fringe of fine grained deep marine systems often exhibits complex sedimentary facies and facies associations because the presence of clay promotes the development of transient turbulent flows with complex depositional properties relatively little is known about the variation of current induced sedimentary structures found within these facies this study provides the first comprehensive description and interpretation of mixed sandstone mudstone bedforms observed in the fringe of the mud rich submarine fan that makes up the aberystwyth grits group and borth mudstone formation wales united kingdom using textural and structural descriptions 158 bedforms in sediment gravity flow deposits were characterized into three main types classic sandy current ripples large current ripples and low amplitude bed waves the sandy current ripples comprise clean sandstone with average heights and lengths of 11 mm and 141 mm respectively the large current ripples are composed of mixed sandstone mudstone and possess greater dimensions than the sandy current ripples with an average height of 19 mm and an average length of 274 mm the low amplitude bed waves are long thin bedforms composed commonly of mixed sandstone mudstone with an average height and length of 10 mm and 354 mm respectively the large current ripples and low amplitude bed waves are strikingly similar to experimental bedforms produced under decelerating mixed sand mud flows and are interpreted to form beneath transitional flows with enhanced and attenuated near bed turbulence respectively from the fringe to the distal fringe of the fan the dominant bedform type changed from sandy current ripples via large current ripples to low amplitude bed waves suggesting that the flows changed from turbulent to increasingly turbulence modulated it is proposed that the flow reynolds number reduced reflecting this flow transformation from a combination of constant or decreasing flow height flow deceleration from sediment deposition and increasing flow viscosity due to the shear thinning nature of clay rich suspensions large current ripples and low amplitude bed waves are likely to be common in the fringe of other submarine fans the presence and spatial trends in mixed sand mud bedform types may be an important tool in interpreting fan fringe environments

basin floor fans in the north sea sequence stratigraphic models vs sedimentary facies discussion original article shanmugan g r b bloch s m mitchell g w j beamish r j hodgkinson j e damuth t straume s e syvertsen and k e shields 1995 aapg bulletin v 79 p 477 512

duplex like structures in submarine fan channels ouachita mountains arkansas submarine fan channel sequences of the jackfork formation lower pennsylvanian at degray dam section in the ouachita mountains arkansas contain discrete units 10 75 cm thick with moderately dipping 25 40 sigmoidal imbricate slices adjacent units with opposing imbricate slices are common the sigmoidal structures are similar in geometry to a tectonic feature known as a duplex a tectonic origin of sigmoidal structures however seems unlikely because opposing directions of imbrication in adjacent units would require an unrealistic tectonic movement history for the area we propose that the jackfork sigmoidal structures were formed by a process kinematically similar to that responsible for generating duplex structures unlike tectonic duplexes however the sigmoidal structures were formed by soft sediment deformation of sand and mud layers as high energy sediment gravity flows glided over these layers sediment gravity flows responsible for forming the sigmoidal deformation were probably generated by slumping of adjacent channel walls dip direction of sigmoidal slices is perpendicular to channel axes thus recognition of sigmoidal deformation structures may be useful in inferring the trend of channels in ancient submarine fan complexes

an integrated chemo and sequence stratigraphic framework of the early pennsylvanian deepwater outcrops near kirby arkansas usa and its implications on remnant basin tectonics abstract the jackfork group in arkansas u s a is a major training ground for academics students and petroleum industry geoscientists interested in deep water exploration and development several superb outcrop sections are exposed and over the years numerous papers have been published on these rocks the kirby sections in western arkansas provide a unique opportunity to build a complete and continuous sequence stratigraphic framework for early pennsylvanian time in the ancient ouachita basin there are 25 outcrops including 12 roadcuts on highway 27 and 13 measured sections in the baumgartner quarry all the measurements and interpretations on the outcrops were integrated with previous work using modern concepts of deepwater turbidite geology including 1 regional tectonic and sequence stratigraphic framework of the stanley group jackfork group and johns valley shale in the ouachita basin 2 deepwater outcrop characterization and correlation from the degray lake section dierks section and big rock quarry which are on the trend of the depositional fairway 3 chemostrata data from key shale layers which are considered as potential correlative condensed sections twenty five key shale samples from kirby degray and dierks sections have been tested using inductively coupled plasma and mass spectrometry icp ms tests an additional 525 samples were later collected for handheld x ray fluorescence xrf tests for both major and trace elements results of sequence and chemostrata analysis indicate that the entire kirby sections consist of at least three 3rd order sequences from the bottom of the jackfork group to the middle of the johns valley group and over ten 4th order sequences caused by a combined effect of tectonic uplift eustatic sea level change mixed sediment provenance and shifting of depositional fairways when the ouachita basin was transitioning from a passive margin to a remnant marine basin rare earth and trace element results are compared with known tectonic data to further pinpoint the tectonic environment of the ouachita basin during early pennsylvanian time which is dominantly a continental arc setting

ten turbidite myths abstract during the past 50 years the turbidite paradigm has promoted many myths related to deep water turbidite deposition john e sanders 1926 1999 a pioneering process sedimentologist first uncovered many of these turbidite myths this paper provides a reality check by undoing 10 of these turbidite myths myth no 1 turbidity currents are non turbulent flows with multiple sediment support mechanisms reality turbidity currents are turbulent flows in which turbulence is the principal sediment support mechanism myth no 2 turbidites are deposits of debris flows grain flows fluidized flows and turbidity currents reality turbidites are the exclusive deposits of turbidity currents myth no 3 turbidity currents are high velocity flows and therefore they elude documentation reality turbidity currents operate under a wide range of velocity conditions myth no 4 high density turbidity currents are true turbidity currents reality ph h kuenen 1950 introduced the concept of turbidity currents of high density based on experimental debris flows not turbidity currents high density turbidity currents are sandy debris flows myth no 5 slurry flows are high density turbidity currents reality slurry flows are debris flows myth no 6 flute structures are indicative of turbidite deposition reality flute structures are indicative only of flow erosion not deposition myth no 7 normal grading is a product of multiple depositional events reality normal grading is the product of a single depositional event myth no 8 cross bedding is a product of turbidity currents reality cross bedding is a product of traction deposition from bottom currents myth no 9 turbidite facies models are useful tools for interpreting deposits of turbidity currents reality a reexamination of the annot sandstone in se france which served as the basis for developing the first turbidite facies model suggests a complex depositional origin by plastic flows and bottom currents myth no 10 turbidite facies can be interpreted using seismic facies and geometries reality individual turbidity current depositional events commonly centimeters to decimeters in thickness cannot be resolved in seismic data all turbidite myths promote falsehood and should be abandoned

quartz arenites of the cambro ordovician kamouraska formation quebec appalachians canada i deep water depositional processes in a continental slope environment the kamouraska formation is an uppermost cambrian lowermost ordovician quartz arenite dominated unit of controversial origin deposited on the southeastern slope of laurentia bordering the iapetus ocean it is exposed in the quebec appalachians on the south shore of the st lawrence estuary the formation consists of basal polymictic conglomerate and overlying massive sheet like quartz arenite the conglomerate beds are reversely and reversely to normally graded the quartz arenite beds are generally massive although they may show coarse tail grading beds containing full or partial bouma sequences are rare paleoflow directions from ripple cross lamination ripple marks on bed surfaces and sole marks point towards southeast south and southwest the clastic sediments of the kamouraska were transported into the deep sea by sediment gravity flows that evolved from hyperconcentrated to concentrated density flows and then to turbidity currents the depositional environment is interpreted to have been a

steady state concepts and static liquefaction of silty sands the results from an experimental study on silty sands are presented and evaluated in view of the framework of critical state or steady state soil mechanics drained and undrained compression tests were performed on nevada sand containing nonplastic silt the drained and undrained steady state lines diverged this divergence was caused by the tendency for static liquefaction at low pressures results from undrained tests with different initial void ratios produced different steady state lines unique steady state lines may therefore not always exist for silty sands denser specimens liquefied at low confining pressures while looser specimens at higher confining pressures showed stable behavior thus a unique relation between void ratio and confining pressure namely the steady state line may not represent the behavior of loose silty sands this occurs because silty sands exhibit reverse behavior characteristics more dilative behavior is observed with increasing confining pressure under undrained shearing load and deformation control testing was performed to evaluate the effect of strain rate compressibility was examined as an alternative measure of liquefaction potential

depositional origin of tuffaceous units in the pliocene upper siwalik subgroup jammu india nw himalaya during late pliocene times extrabasinally derived acidic volcanic ashes were deposited as distal pyroclastic fallout in upland interfluvial lacustrine settings in the northwestern part of the siwalik basin these ash beds occur as a bentonitized tuff band and tuffaceous mudstones in the jammu region of india we located and described 12 outcrops of this conspicuous geographically widespread bentonitized tuff band and tuffaceous mudstone association at the same stratigraphic level coincident with the gauss matuyama boundary at 2 48 ma this bentonitized tuff band and tuffaceous mudstone association represents a stratigraphic marker horizon in the diachronous and sporadic vertebrate fauna yielding siwalik strata the claystone siltstone and sandstone units and embedded bentonitized tuff band and tuffaceous mudstone beds represent a coarsening upward sequence reflecting deposition in lacustrine proximal and distal bottomsets pro delta foresets and mouth bar facies capped by fluvial topsets this study reports a chain of four contemporaneous palaeolake basins at this stratigraphic level which ranged in length from 2 to 7 km

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion the pennsylvanian jackfork group in the ouachita mountains of arkansas and oklahoma has conventionally been interpreted by many workers including us as a classic flysch sequence dominated by turbidites in a submarine fan setting however normal size grading and bouma sequences indicative of turbidite deposition are essentially absent in these sandstone beds they appear massive i e structureless in outcrop but when slabbed reveal diagnostic internal features these beds exhibit sharp and irregular upper bedding contacts inverse size grading floating mudstone clasts a planar clast fabric lateral pinch out geometries moderate to high detrital matrix up to 25 sigmoidal deformation duplex structures and contorted layers all these features indicate sand mplacement by debris flows mass flows and slumps mud matrix in these sandstones was sufficient to provide cohesive strength to the flow discrete units of current ripples and horizontal laminae have been interpreted to represent traction processes associated with bottom current reworking the dominance of sandy debris flow and slump deposits nearly 70 at degray spillway section and bottom current reworked deposits 40 at kiamichi mountain section and the lack of turbidites in the jackfork group have led us to propose a slope setting our rejection of a submarine fan setting has important implications for predicting sand body geometry and continuity because deposits of fluidal turbidity currents in fans are laterally more continuous than those of plastic debris flows and slumps on slopes a turbidite dominated fan model would predict an outer fan environment with laterally continuous sheetlike sandstones for the jackfork group in southern oklahoma and western arkansas whereas a debris flow slump model would predict predominantly a slope environment with disconne ted sandstone bodies for the same area

determination of offset across the northern margin of the wichita uplift southwest oklahoma the wichita uplift represents a tectonic element within the ancestral rocky mountains a series of basement involved uplifts and associated basins within the foreland of the ouachita orogen contrasting tectonic models for the evolution of the wichita uplift are evaluated by i analyzing the suite of structures within the frontal fault zone which separates the uplift from the adjoining anadarko basin and ii undertaking a palinspastic restoration of houton group late ordovician devonian thickness trends between the basin and the frontal fault zone to estimate the magnitude and sense of offset across the principal uplift bounding faults cross sections from uplift to basin show basement involved thrusts and folds similar to those recognized within the laramide late cretaceous tertiary foreland of the rocky mountains structural patterns in map view possess elements that have been previously interpreted as resulting from reverse slip and or left slip on the uplift bounding faults palinspastic restoration of isopach patterns between the frontal fault zone and anadarko basin indicates that offset across the frontal faults may be explained by oblique slip left reverse slip on the uplift bounding faults the component of left slip is nearly an order off magnitude less than proposed in some previous models of carboniferous tectonism within the foreland of the ouachita orogen

on the frequency distribution of turbidite thickness the frequency distribution of turbidite thickness records information on flow hydrodynamics initial sediment volumes and source migration and is an important component of petroleum reservoir models however the nature of this thickness distribution is currently uncertain with log normal or negative exponential frequency distributions and power law cumulative frequency distributions having been proposed by different authors a detailed analysis of the miocene marnoso arenacea formation of the italian apennines shows that turbidite bed thickness and sand interval thickness within each bed have a frequency distribution comprising the sum of a series of log normal frequency distributions these strata were deposited predominantly in a basin plain setting and bed amalgamation is relatively rare beds or sand intervals truncated by erosion were excluded from this analysis each log normal frequency distribution characterizes bed or sand interval thickness for a given basal grain size or basal bouma division measurements from the silurian aberystwyth grits in wales the cretaceous great valley sequence in california and the permian karoo basin in south africa show that this conclusion holds for sequences of disparate age and variable location the median thickness of these log normal distributions is positively correlated with basal grain size the power law exponent relating the basal grain size and median thickness is different for turbidites with a basal a or b division and those with only c d and e divisions these two types of turbidite have been termed thin bedded and thick bedded by previous workers a change in the power law exponent is proposed to be related to i a transition from viscous to inertial settling of sediment grains and ii hindered settling at high sediment concentrations the bimodal thickness distribution of thin bedded and thick bedded turbidites noted by previous workers is explained as the result of a change in the power law exponent this analysis supports the view that a and b divisions were deposited from high concentration flow components and that distinct grain size modes undergo different depositional processes summation of log normal frequency distributions for thin and thick bedded turbidites produces a cumulative frequency distribution of thickness with a segmented power law trend thus the occurrence of both log normal and segmented power law frequency distributions can be explained in a holistic fashion power law frequency distributions of turbidite thickness have previously been linked to power law distributions of earthquake magnitude or volumes of submarine slope failure the log normal distribution for a given grain size class observed in this study suggests an alternative view that turbidite thickness is determined by the multiplicative addition of several randomly distributed parameters in addition to the settling velocity of the grain sizes present

subaerial debris flow deposition in the upper paleozoic cutler formation western colorado abstract outcrops of the lower part of the cutler formation near gateway colorado contain proximal alluvial fan deposits of two principal lithofacies the diamictite lithofacies d consists of a variety of sharply bounded massive muddy beds which are interpreted as deposits of subaerial debris flows the gravelly sandstone lithofacies s consists of amalgamated beds of laminated and cross bedded conglomeratic sandstones which are interpreted as water deposited sediments clasts in s are rarely larger than 0 5 m in maximum diameter but clasts in d are commonly much larger up to 8 m both normal and inverse grading are visible in d but grading is generally not well developed in either lithofacies imbrication of clasts although more pronounced and more consistent in s is fairly commo in both lithofacies four subfacies of diamictite are distinguishable on the basis of clast packing and grading massive matrix supported dram graded matrix supported dmg inversely graded clast supported dci and massive clast supported dcm given the hydrodynamic and rheologic properties of debris flows as reported by previous workers four debris flow regimes are postulated on the basis of varying water content and clast interaction subfacies dram and drag typify deposits of flows having viscous clast interactions subfacies dci represents deposits of flows having inertial or colliding clast interactions subfacies dram comprises deposits of flows with demonstrably high yield strengths subfacies dcm represents deposits of flows in which yield strength was insufficient to support most clasts this classification specifically recognizes turbulence selective deposition and bedload transport of clasts as essential characteristics of certain dilute debris flows it also accommodates as debris flow deposits some beds which have features usually associated with aqueous deposition including clast frameworks channelization imbrication and normal grading

jackfork group southeastern oklahoma new gas play in the ouachita overthrust recent discovery of natural gas in sandstones of the jackfork group of southeastern oklahoma has led to revised interpretations of hydrocarbon potential in the ouachita thrust province of eastern oklahoma jackfork reservoirs consist of fine to very fine grained submarine fan lobe sandstones with low matrix permeability and porosity production is dependent upon natural fractures enhanced in most cases by artificial stimulation individual wells have produced at rates of 1 3 5 7 mcf footnote per day and possess estimated reserves in the range of 2 0 7 6 gcf footnote hyperbolic decline suggests gas contribution from the matrix possibly due to the presence of microfractures drilling has concentrated on two subsidiary thrust blocks in the hanging wall of the ti alley thrust southern latimer county however recent outcrop petrographic and sedimentological analyses have shown that traditional depositional models of the jackfork are overly limited and that potential jackfork reservoirs exist across a broad area to the south of the current play such analyses have revealed the existence of thick medium coarse grained channel sequences at a number of localities in the lynn mountain syncline similar sequences may also exist well to the south in the boktukola syncline where thick sand intervals have been identified petrographic study of samples from the lynn mountain syncline suggests that channel sequences may have significantly higher reservoir quality than is found in productive jackfork sandstones to the north traditional assumptions pos ulating low regional hydrocarbon potential for the jackfork therefore stand in need of revision

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

evidence for carbonate platform failure during rapid sea level rise ca 14 000 year old bioclastic flow deposits in the lesser antilles bioclastic flow deposits offshore from the soufriere hills volcano on montserrat in the lesser antilles were deposited by the largest volume sediment flows near this active volcano in the last 26 kyr the volume of these deposits exceeds that of the largest historic volcanic dome collapse in the world which occurred on montserrat in 2003 these flows were most probably generated by a large submarine slope failure of the carbonate shelf comprising the south west flank of antigua or the east flank of redonda adjacent islands that are not volcanically active the bioclastic flow deposits are relatively coarse grained and either ungraded or poorly graded and were deposited by non cohesive debris flow and high density turbidity currents the bioclastic deposit often comprises multiple sub units that cannot be correlated between core sites some located just 2 km apart multiple sub units in the bioclastic deposit result from either flow reflection stacking of multiple debris flow lobes and or multi stage collapse of the initial landslide this study provides unusually precise constraints on the age of this mass flow event that occurred at ca 14 ka few large submarine landslides have been well dated but the slope failures that have been dated are commonly associated with periods of rapid sea level change

subsurface structure of the eastern arkoma basin analysis of 425 km of seismic reflection data in the eastern arkoma basin reveals a structure and history quite different from those previously reported for the arkoma basin the eastern arkoma basin has three structural styles that formed in the following chronological order deep steep normal faults shallow listric normal faults and thrust faults the origin of the structural styles and the paleozoic history of the eastern arkoma basin may be summarized as follows late proterozoic or early cambrian rifting was followed by deposition of cambrian through upper mississippian strata on a passive plate margin the mississippian pennsylvanian boundary marks a time of major down to the south normal faulting with coincident folding of the footwall blocks and truncation of t e faulted and folded terrain by a pre morrowan mississippian pennsylvanian unconformity the unconformity slopes southward and steepens locally across the erosionally truncated footwall blocks during the pennsylvanian down to the south listric normal faults cut the atokan and morrowan sections and merged with but did not displace the steeper segments of the sub morrowan unconformity surface folds north of the ross creek thrust are rollover anticlines overlying these listric normal faults major deformation in the eastern arkoma basin terminated with emplacement of the ross creek thrust in the late pennsylvanian

upper pleistocene turbidite sand beds and chaotic silt beds in the channelized distal outer fan lobes of the mississippi fan cores from a mississippi outer fan depositional lobe demonstrate that sublobes at the distal edge contain a complex local network of channelized turbidite beds of graded sand and debris flow beds of chaotic silt off lobe basin plains lack siliciclastic coarse grained beds the basin plain mud facies exhibit low acoustic backscatter on seamarc ia sidescan sonar images whereas high acoustic backscatter characteristic of the lobe sand and silt facies the depth of the first sand silt layer correlates with relative backscatter intensity and stratigraphic age of the distal sublobes i e shallowest sand highest backscatter and youngest sublobe the high proportion 50 of chaotic silt compared to graded sand in the distal outer fan sublobes may be related to the unstable muddy canyon wall source areas of the extensive mississippi delta fed basin slope a predominace of chaotic silt in cores or outcrops from outer fan lobes thus may predict similar settings for ancient fans

the bouma sequence and the turbidite mind set abstract conventionally the bouma sequence bouma a h 1962 sedimentology of some flysch deposits a graphic approach to facies interpretation elsevier amsterdam 168 pp composed of ta tb tc td and te divisions is interpreted to be the product of a turbidity current however recent core and outcrop studies show that the complete and partial bouma sequences can also be interpreted to be deposits formed by processes other than turbidity currents such as sandy debris flows and bottom current reworking many published examples of turbidites most of them hydrocarbon bearing sands in the north sea the norwegian sea offshore nigeria offshore gabon gulf of mexico and the ouachita mountains are being reinterpreted by the present author as dominantly deposits of sandy debris flows and bottom current reworking with only a minor percentage of true turbidites i e deposits of turbidity currents with fluidal or newtonian rheology in which sediment is suspended by fluid turbulence this reinterpretation is based on detailed description of 21 000 ft 6402 m of conventional cores and 1200 ft 365 m of outcrop sections the predominance of interpreted turbidites in these areas by other workers can be attributed to the following 1 loose applications of turbidity current concepts without regard for fluid rheology flow state and sediment support mechanism that result in a category of turbidity currents that includes debris flows and bottom currents 2 field description of deep water sands using the bouma sequence an interpretive model that invariably leads to a model driven turbidite interpretation 3 the prevailing turbidite mind set that subconsciously forces one to routinely interpret most deep water sands as some kind of turbidites 4 the use of our inability to interpret transport mechanism from the depositional record as an excuse for assuming deep water sands as deposits of turbidity currents 5 the flawed concept of high density turbidity currents that allows room for interpreting debris flow deposits as turbidites 6 the flawed comparison of subaerial river currents fluid gravity flows dominated by bed load transport with subaqueous turbidity currents sediment gravity flows dominated by suspended load transport that results in misinterpreting ungraded or parallel stratified deep sea deposits as turbidites and 7 the attraction to use obsolete submarine fan models with channels and lobes that require a turbidite interpretation although the turbidite paradigm is alive and well for now the turbidites themselves are becoming an endangered facies

slump dominated upper slope reservoir facies intra qua iboe pliocene edop field offshore nigeria abstract an integration of sedimentologic and 3d seismic data provides a basis for unraveling complex depositional processes and sand distribution of the intra qua iboe iqi reservoir pliocene edop field offshore nigeria nearly 3 000 feet of conventional core was examined in interpreting slump slide debris flow bottom current turbidity current pelagic hemipelagic wave and tide dominated facies the iqi was deposited on an upper slope in close proximity to the shelf edge through time as the shelf edge migrated seaward deposition began with a turbidite channel dominated slope system iqi 1 and 2 and progressed through a slump debris flow dominated slope system iqi 3 the principal reservoir to a tide and wave dominated collapsed shelf edge deltaic system iqi 4 using seismic time slices and corresponding depositional facies in the core a sandy open quotes fairway open quotes has been delineated in the iqi 3 because of differences in stacking patterns of sandy and muddy slump intervals seismic facies show 1 both sheet like and mounded external forms geometries and 2 parallel continuous as well as chaotic hummocky internal reflections in wireline logs slump facies exhibits blocky coarsening up fining up and serrated motifs in the absence of conventional core slump facies may be misinterpreted and even miscorrelated because seismic facies and log motifsmore of slumps and debris flows tend to mimic properties of turbidite fan deposits the slump dominated reservoir facies is composed of unconsolidated fine grained sand thickness of individual units varies from 1 to 34 feet but amalgamated intervals reach a thickness of up to 70 feet and apparently form connected sand bodies porosity commonly ranges from 20 to 35 horizontal permeability commonly ranges from 1 000 to 3 000 md less

fluidization and injection in the deep water sandstones of the eocene alba formation uk north sea the nauchlan member of the late eocene alba formation uk north sea consists of a deep water channel fill that was extensively modified by post depositional sand remobilization and injection sandstone textures facies associations and the geometry of the channel fill were affected a suite of sand rich facies was produced by large scale fluidization and injection within the channel fill and above it these facies termed here unstratified facies are characterized by the absence of stratification surfaces and by discordant relationships with bedding in the adjacent succession they reflect variable degrees of disruption of the primary sedimentary structures caused by escaping pore fluid the velocity of which is estimated at least in the order of 0 1 ms 1 adjacent mudstones were severely disrupted by hydraulic fracturing and fragments of fractured mudstone were incorporated into the fluidized sand average porosity was decreased in the sandstones affected by fluidization two main phases of sand injection are inferred to occur at different burial depths a shallow burial phase below 100 m produced thin dykes with ptygmatic folds the second phase occurred at the boundary between eocene and oligocene 300 m burial depth and resulted in large scale tabular wing like dykes that project from the edges of the channel fill the significant pore fluid overpressure which was required to hydraulically fracture the thick mudstone seal and to fluidize the large volume of sand was likely to be built up by static liquefaction of the source sand and was possibly enhanced by hydrocarbon gas influx

carbonate debris flows cow head group western newfoundland abstract the cow head group is an allochthonous cambro ordovician sequence of deep water limestone conglomerates mudstones to grainstones minor quartz sandstones siltstones and shales platy clast conglomerates and boulder rich megaconglomerates as much as 100 m thick exhibit features similar to those described for subaerial debris flows that is flat sharp bases with only minor evidence for erosion poorly developed clast fabric with tilting of platy clasts at right angles to the flow direction boulders floating within flows or projecting above the tops of flows irregular flow tops indicating primary relief above the sea floor and tapered flow margins snouts snout geometry and the extent of boulder projection both allow calculation of debris static strength these results combined with measured flow thickness permit calculation of minimum and maximum paleoslope gradients original debris static strengths were in the range of 103 to 105 dynes cm2 similar to the observed range in subaerial flows calculations yield bottom gradients of l l 8 but independent field data suggest that the paleoslope dip was on the order of only a few degrees this constraint suggests that debris strength was substantially reduced during flow probably by excess pore fluid pressures thus permitting flow on very gentle slopes the paleoslope orientations used in this study are substantially different from those previously published by hubert et at 1977

deposition of ungraded muds from high density non turbulent turbidity currents turbidity current deposits of mud have recently been found up to 10m in thickness resulting from single depositional events1 2 turbidites 1 5 m thick from the madeira abyssal plain3 4 display long segments with little vertical change of grain size5 6 this suggests that the currents froze in some way making them unable to sort sediment here we suggest that a decline in flow speed of these currents led to a concentration gradient in silt close to the bed that was sufficiently steep to stratify the flow a concentration gradient of 18 kg m 3 over 1 5 m height gives a layer richardson number above the critical value of 0 25 for damping of turbulence we propose that with turbulence severely damped a dense suspension of fine material consolidates like a static suspension while continuing to flow downslope the current changes from a fully turbulent flow to a decelerating flow with suppressed turbulence and increasing density in the latter state interparticle forces prevent differential settling of the coarser grains

evolution of a permian carbonate platform to siliciclastic basin indochina plate thailand abstract in thailand during the permian an extensive carbonate platform developed on the margin of the indochina plate and near to a coeval and deeper siliciclastic dominated marine basin this basin separated the indochina plate to the east from the shan thai plate to the west sedimentation in the area of both platform pha nok khao platform and basin nam duk basin was ended by a late permian early triassic orogenic event that caused closure of the palaeo tethys ocean tectonism has controlled the pattern of platform sedimentation and supplies of carbonate and clastic sediments into the basin area the pha nok khao platform developed on an extensive distally steepened ramp like margin along which carbonates and siliciclastics accumulated adjacent to this platform to the west the nam duk basin received coeval hemipelagic siliciclastics and minor amounts of carbonates biostratigraphic evidence based on foraminiferal assemblages suggests an early to middle permian age equivalence between platform and basin lithofacies the platform strata are exposed along the loei fold and thrust belt in northeast thailand and basin strata are exposed within the phetchabun fold and thrust belt in central thailand respectively the two belts extend in a north south direction and their rocks exhibit extensive karstification on the basis of seismic data platform lithologies extend further east in the subsurface beneath the continental sediments of the khorat group into kampuchea and laos facies groups of the platform environments include restricted platform platform interior and outer platform the facies groups of the basin environments include basin margin and basin plain minor layers of volcaniclastics and green coloured tuffites are interbedded with both the platform carbonate layers and basinal pelagic layers suggesting active volcanism during sedimentation the carbonate lithofacies of the shallow platform to the east in the loei fold belt grade westward into turbidites in the phetchabun fold belt and include shales and sandstones with minor carbonates farther to the west they pass into hemipelagic lithofacies of shale and carbonate lithologies and fauna of the limestones suggest tropical to subtropical climate during deposition

traction carpet stratification in turbidites fact or fiction abstract the spaced stratification that characterizes some thick deep water sandstones consists of a stack of layers 5 10 cm thick that are inversely graded at their base and structureless at their top these layers have been attributed to deposition from a succession of collapsed inertia layers traction carpets prior to collapse each layer was believed to have been maintained by shear from the overriding turbidity current this depositional model is based on the mistaken assumption that the distribution of shear stress in such a traction carpet is indistinguishable from the distribution of shear stress in a grain flow on a steep slope instead shear stress in an externally sheared traction carpet should be approximately constant from the top to the base of the layer and deposition sho ld be a gradual process leaving no record of sequentially active inertia layers inertia layers that do form under large turbidity currents are probably never as thick as 5 10 cm based on available data from shear cell experiments instead inertia layers are probably about 1 cm thick similar to the thickness of the inversely graded basal part of each layer in field examples of spaced stratification the rest of each inversely graded stratum probably forms due to rapid fallout from suspension the basal inversely graded 1 cm is believed to record strong shear that may accompany impingement on the bed of large turbulent eddies hence spaced stratification may not be a structure produced beneath steady flows but may record strong y fluctuating hydrodynamic conditions and vigorous burst sweep cycles in large turbidity currents

the morphology setting and processes of the afen slide abstract identified in 1996 during an environmental survey for the atlantic frontiers environment network the afen slide lies around 95 km northwest of the shetland islands the head of the slide is at a water depth of 830 mbsl and the debris lobe stretches to over 1120 mbsl along a slope varying from around 0 7 to 2 5 the overall length head scarp to toe of lobe of the slide is in excess of 12 km and the maximum width attained is around 4 5 km the relative timing of the various phases can be determined from the morphology imaged using seabed picks from 3d exploration seismics and high resolution deep tow boomer data these seem to show at least four major phases of failure and several distinct modes of sediment transport ranging from hydroplaning to block sliding the most likely trigger for the failure is a seismic event focused on the nearby victory transfer zone sensitising factors include the presence of contouritic sands directly beneath the surface of rupture these would serve as a plane of weakness and under seismic loading may further weaken due to liquefaction indeed previous studies have shown that the slope in this area is stable in the absence of external triggers the processes of sediment transport subsequent to failure are also investigated using sediment cores as well as the 2d and 3d seismic and appear to indicate that flow transformation occurred in at least the first phase of mass movement

submarine fan sedimentation ouachita mountains arkansas and oklahoma abstract more than 10 000 m 32 800 ft of interbedded sandstones and shales comprise the upper mississippian and lower pennsylvanian flysch succession stanley jackfork johns valley atoka in the ouachita mountains of arkansas and oklahoma deposited primarily by turbidity current and hemipelagic processes in bathyal and abyssal water depths these strata formed major submarine fan complexes that prograded in a westward direction along the axis of an elongate remnant ocean basin that was associated with the collision and suturing of the north american and african south american plates a longitudinal fan system is visualized as the depositional framework for these strata which were deposited in a setting analagous to the modern bengal fan of the indian ocean facies analysis of the jackfork formation indicates that inner fan deposits are present in the vicinity of little rock arkansas middle fan channel and interchannel deposits occur at degray dam and friendship arkansas and outer fan depositional lobe deposits are present in southeastern oklahoma boulder bearing units olistostromes often with exotic clasts were shed laterally into the ouachita basin they occur throughout the flysch succession and in all fan environments i e inner middle and outer this relationship may serve as a useful criterion for recognizing analogous longitudinal fan systems in the rock record

can liquefied debris flows deposit clean sand over large areas of sea floor field evidence from the marnoso arenacea formation italian apennines the marnoso arenacea formation in the italian apennines is the only ancient rock sequence where individual submarine sediment density flow deposits have been mapped out in detail for over 100 km bed correlations provide new insight into how submarine flows deposit sand because bed architecture and sandstone shape provide an independent test of depositional process models this test is important because it can be difficult or impossible to infer depositional process unambiguously from characteristics seen at just one outcrop especially for massive clean sandstone intervals whose origin has been controversial beds have three different types of geometries facies tracts in downflow oriented transects facies tracts 1 and 2 contain clean graded and ungraded massive sandstone deposited incrementally by turbidity currents and these intervals taper relatively gradually downflow mud rich sand deposited by cohesive debris flow occurs in the distal part of facies tract 2 facies tract 3 contains clean sandstone with a distinctive swirly fabric formed by patches of coarser and better sorted grains that most likely records pervasive liquefaction this type of clean sandstone can extend for up to 30 km before pinching out relatively abruptly this abrupt pinch out suggests that this clean sand was deposited by debris flow in some beds there are downflow transitions from turbidite sandstone into clean debrite sandstone suggesting that debris flows formed by transformation from high density turbidity currents however outsize clasts in one particular debrite are too large and dense to have been carried by an initial turbidity current suggesting that this debris flow ran out for at least 15 km field data indicate that liquefied debris flows can sometimes deposit clean sand over large 10 to 30 km expanses of sea floor and that these clean debrite sand layers can terminate abruptly

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion authors reply

is the turbidite facies association scheme valid for interpreting ancient submarine fan environments although turbidite facies reflect only processes of deposition turbidite facies associations are routinely used to identify ancient submarine fan subenvironments e g upper fan channel lobe etc the assumption that process of deposition also reflects environment of deposition may not be valid for the following reasons 1 mutti and ricci lucchi9s facies association scheme for submarine fans has been developed exclusively from ancient turbidite sequences however the true relationship between such turbidite facies associations and related fan subenvironments has not been confirmed from modern fans 2 individual channel levee systems of many modern submarine fans are in many cases large enough to contain the entire ancient fan systems on which these facies associations are based 3 large channel levee systems comparable to those of modern fans have not been recognized in outcrops consequently the validity of turbidite facies associations for interpreting ancient submarine fan subenvironments must be considered tenuous until confirmed in modern fans

combined tectonic sediment supply driven cycles in a lower carboniferous deep marine foreland basin moravice formation czech republic the lower carboniferous moravian silesian culm basin mscb represents the easternmost part of the rhenohercynian system of collision related deep water foreland basins culm facies the upper visean moravice formation mf of the mscb shows a distinct cyclic stratigraphic arrangement two major asymmetric megacycles bounded by basal sequence boundary each about 500 to 900 m thick have been revealed the megacycles start with 50 to 250 m thick basal segments of erosive channels overbank successions and slope apron deposits interpreted as lowstand turbidite systems up section they pass into hundred metre thick fine grained low efficiency turbidite systems palaeocurrent data show two prominent directions basin axis parallel ssw nne directions which are abundant in the whole mf and basin axis perpendicular to oblique w e to nw se directions which tend to be confined to the basal parts of the megacycles or channel lobe transition systems in their upper parts based on the facies characteristics palaeocurrent data sandstone composition data and trace fossil distribution data we suggest a combined tectonics sediment supply driven model for the mf basin fill periods of increased tectonic activity resulted in slope oversteepening probably combined with increased rate of lateral w e sediment supply into the basin producing the basal sequence boundary and the subsequent lowstand turbidite systems during subsequent periods of tectonic quiescence the system was filled mainly from a distant southern point source producing the thick low efficiency turbidite systems consistently with the previous models our own sediment composition data indicate a progressively increasing sediment input from high grade metamorphic and magmatic sources up section most probably related to an uplift in the source area and progressive unroofing of its structurally deeper crustal parts the first occurrence of the cruziana nereites ichnofacies in sand rich turbidite systems in the youngest parts of the mf go el to go spi zone supported by rapidly increasing quartz concentrations in sandstones is thought to indicate a transition from generally underfilled to generally overfilled phase in evolution of the mscb basin this transition may be linked to the onset of upper visean phase of northward basin fill progradation assumed by previous authors

visualization of the internal structure of the massive division in experimental sediment gravity flow deposits by mapping of grain fabric abstract a method for mapping of grain fabric is proposed for analysis of the cryptic internal structure of massive sedimentary units the method is applied to the analysis of an experimental debris flow deposit revealing a number of characteristic features of this type of mass sedimentation the debris flow was simulated in the laboratory using a channel inclined 30 opening onto a 10 slope and transverse thin sections were prepared from four longitudinal points in the depositional lobe back scattered electron images of the sections obtained by scanning electron microscopy were processed and analyzed by mapping of grain fabric using an automated image analysis procedure although the samples appear structureless by macroscopic observation the grain fabric map reveals a range of sedimentary features including distinctive lineations from lower upcurrent to upper downcurrent in the most proximal section representing synsedimentary thrusts a steepening upward trend of grain imbrication angle in intermediate samples with very low angle imbrication in the basal horizon indicative of high shear rate flow and complex imbrication features in the most distal samples this analysis reveals that massive debris flow deposits actually contain a range of distinctive structures which are characteristic of the mode of deposition and which are not identifiable by visible inspection or analysis of grain size or color the proposed method is therefore of great utility for the investigation and characterization of massive deposits

ouachita appalachian juncture a paleozoic transpressional zone in the southeastern u s a the northern margin of gondwana collided with the southern margin of the north american craton in the late paleozoic 330 265 ma near normal compressional stresses generated where the trend of the north american margin was nearly perpendicular to gondwana s plate motion vector closure direction caused extensive crustal shortening and decollement thrusting within the sedimentary section the appalachian and ouachita fold belts are the erosional remnants of this collision on the north american margin transecting the ouachita fold belt are several zones of late paleozoic transcurrent faulting the val verde ardmore anadarko and reelfoot zones they occur where the precollision margin of the north american craton was oriented oblique or parallel to the closure direct on with gondwana stresses generated within these zones during the collision were transpressional rather than simply compressional and gave rise to high angle faulting high amplitude vertical displacements and the emplacement of positive flower structures in the val verde and ardmore anadarko basins these features have proven to be major structural traps for oil and gas on the basis of seismic and well data this study identifies a zone of complex structures including positive flower structures in the subsurface paleozoic section of kemper county in east central mississippi the region is considered to be another transpressional zone analogous to the val verde ardmore anadarko and reelfoot zones the kemper county zone separates and truncates the appalachian valley and ridge fo d belt in the subsurface from the mississippi ouachita deformed belt to the west and is therefore also identified as the juncture between the ouachita and appalachian fold belt systems in the southeastern u s a

beds comprising debrite sandwiched within co genetic turbidite origin and widespread occurrence in distal depositional environments co genetic debrite turbidite beds occur in a variety of modern and ancient turbidite systems their basic character is distinctive an ungraded muddy sandstone interval is encased within mud poor graded sandstone siltstone and mudstone the muddy sandstone interval preserves evidence of en masse deposition and is thus termed a debrite the mud poor sandstone siltstone and mudstone show features indicating progressive layer by layer deposition and are thus called a turbidite palaeocurrent indicators ubiquitous stratigraphic association and the position of hemipelagic intervals demonstrate that debrite and enclosing turbidite originate in the same event detailed field observations are presented for co genetic debrite turbidite beds in three widespread sequences of variable age the miocene marnoso arenacea formation in the italian apennines the silurian aberystwyth grits in wales and quaternary deposits of the agadir basin offshore morocco deposition of these sequences occurred in similar unchannellized basin plain settings co genetic debrite turbidite beds were deposited from longitudinally segregated flow events comprising both debris flow and forerunning turbidity current it is most likely that the debris flow was generated by relatively shallow few tens of centimetres erosion of mud rich sea floor sediment changes in the settling behaviour of sand grains from a muddy fluid as flows decelerated may also have contributed to debrite deposition the association with distal settings results from the ubiquitous presence of muddy deposits in such locations which may be eroded and disaggregated to form a cohesive debris flow debrite intervals may be extensive 26 x 10 km in the marnoso arenacea formation and are not restricted to basin margins such long debris flow run out on low gradient sea floor 0 1 may simply be due to low yield strength 50 pa of the debris water mixture this study emphasizes that multiple flow types and transformations between flow types can occur within the distal parts of submarine flow events

amalgamation surfaces bed thicknesses and dish structures in sand rich submarine fans numeric differences in channelized and unchannelized deposits and their diagnostic value abstract hydraulic differences between channelized and unchannelized flows in sand rich submarine fans result in different distributions of amalgamation surfaces bed thicknesses and dish structures in successions of these two different environments distribution trends of these fabrics were quantified for the sand rich fans of the reiselsberger sandstein cenomanian turonian these trends can be used as criteria to distinguish channelized from unchannelized paleoenvironments of sand rich submarine fans amalgamation surfaces in the studied fans channelized regions are considerably more abundant than in the unchannelized fan areas in unchannelized deposits tabular amalgamation surfaces outnumber nontabular ones whereas the opposite occurs in channelized successions these results indicate a higher degree of erosive power of gravity driven sediment flows in channels as a result of a greater flow thickness higher flow velocity and turbulence the average turbidite layer thickness in channelized successions is markedly greater than in unchannelized deposits layer as defined herein this is mainly attributed to the combined effects of differences in sediment fall out rate and the inefficiency of sand rich suspensions to transport sand in the proximal and channelized fan areas more sediment is deposited from a flow in the form of a layer than in distal unchannelized fan regions despite a higher degree of erosion in channels the greater average bed thickness in channel fills is a function of layer thickness and more frequent amalgamations bed as defined herein dish structures seem to be considerably more common in midfan than in outer fan successions this may indicate a higher sedimentation rate from individual suspension currents in midfan areas

incised submarine canyons governing new evidence of early triassic rifting in east greenland abstract regional studies of the uppermost permian and lowermost triassic successions in central east greenland have shown that sedimentation took place in half grabens during two phases of active rifting the permian triassic boundary locally contains submarine canyons up to several kilometres wide and several tens of metres deep formed in latest permian or earliest triassic times sandy and conglomeratic turbidites filling the canyons are highly variable in architecture depending on the structural setting and the geometry of the submarine canyons bounding surfaces also change character because of an asymmetric subsidence pattern of tilted fault blocks the submarine canyons have been studied on wegener halvo where exposures allow tracing of several canyons from the slope to the basin floor setting the canyons are interpreted to have developed from fluvial incised valleys furthest updip on the fault block and from turbidity current erosion further downdip the canyons have a se nw elongation while palaeocurrents were unimodal towards the nw reflecting the dip of the rotated fault block the canyon fill turbidites were deposited by consequent drainage on a nw dipping ramp like hangingwall slope within a half graben in areas between the canyons the permian triassic boundary is onlapped by triassic mudstones of offshore marine origin the studied succession is grouped into two facies associations 1 submarine gravity flow sandstones and conglomerates and 2 suspension deposited shales and mudstones traced down dip the submarine canyon fills display a change from chaotic conglomeratic and coarse sandy high density turbidites proximally to organised sandy turbidites basinwards farthest basinward a remarkable basin floor fan with well developed giant scale foresets is observed this trend reflects canyon widening and a decrease in gradient at the basin floor progradation of the turbidites was probably controlled by westward tilting of the fault block causing a steeper slope and subaerial exposure of a larger part of the proximal hangingwall above the fulcrum this resulted in erosion of the crestal area of the block that is upper permian and older successions and led to an increase in sediment supply to the downdip area accommodation space was created below fulcrum and downdip transgression governed back filling of the submarine canyons the observed eastward onlap of ammonite zones in shales and mudstones between the canyons was contemporaneous with the filling of the canyons a later drowning of the updip catchment caused decrease or shut off of sediment supply leading to deposition of shales and mudstones blanketing the sandy turbidites in the canyons the tilt of the studied fault block is interpreted to have caused simultaneous transgression below the fulcrum and regression with bypass or erosion above the fulcrum it is concluded that the tilted fault block setting has important consequences for sequence stratigraphic interpretations due to the asymmetric subsidence causing drastic changes in bounding surface character tectonism and sediment supply were the main controls on the stratigraphic architecture of the studied lower triassic succession on wegener halvo

textural trends in turbidites and slurry beds from the oligocene flysch of the east carpathians romania deep water sandstone beds of the oligocene fusaru sandstone and lower dysodilic shale exposed in the buza uu valley area of the east carpathian flysch belt romania can be described in terms of the standard turbidite divisions in addition mud rich sand layers are common both as parts of otherwise normal sequences of turbidite divisions and as individual event beds eleven units interpreted as the deposits of individual flows were densely sampled and 87 thin sections were point counted for grain size and mud content s3 ta divisions which form the bulk of most sedimentation units have low internal textural variability but show subtle vertical trends in grain size most commonly coarse tail normal grading is associated with finetail inverse grading the mean grain size can show inverse grading normal grading or a lack of grading but sorting tends to improve upward in most beds fine tail inverse grading is interpreted as resulting from a decreasing effectiveness of trapping of fines during rapid deposition from a turbidity current as the initially high suspended load fallout rate declines if this effect is strong enough the mean grain size can show subtle inverse grading as well thus thick inversely graded intervals in deep water sands lacking traction structures do not necessarily imply waxing flow velocities if the suspendedload fallout rate drops to zero after the deposition of the coarse grain size populations the remaining finer grained flow bypasses and may rework the top of the s3 division forming well sorted coarser grained current structured tt units alternatively the suspended load fallout rate may remain high enough to prevent segregation of fines leading to the deposition of significant amounts of mud along with the sand mud content of the sandstones is bimodal either 3 13 or more than 20 two types of mud rich sandstones were observed coarser grained mud rich sandstones occur towards the upper parts of s3 ta divisions these units were deposited as a result of enhanced trapping of mud particles in the rapidly deposited sediment finer grained mud rich units are interbedded with ripple laminated very fine grained sandy tc divisions during deposition of these units mud floccules were hydraulically equivalent to the very fine sand and silt sized sediment the mud rich sandstones were probably deposited by flows that became transitional between turbidity currents and debris flows during their late stage evolution

stress relations in three recent seismic series in the murcia region southeastern spain abstract in this work we study the relation between the seismicity belonging to three recent seismic series in the murcia region southeastern spain with the coseismic stress changes due to their largest shocks the first series occurred in 1999 near the town of mula with a mainshock magnitude of mw 5 1 the second series occurred in 2002 in the region of bullas 35 km sw from the 1999 series with events of magnitudes mw 5 0 the last one occurred three years later 2005 5 km se from the 2002 series with magnitudes of events mw 4 8 for the analysis we relocated the seismicity of each series next we computed the coseismic stress change produced by its main events and a foreshock and finally tested the possible stress relations inside and among the series based on the coulomb failure stress changes our results show that the mula 1999 main earthquake associated in different publications to the crevillente fault was positively influenced for triggering by the foreshock we also find that the 1999 series aftershocks were jointly influenced for triggering by both the foreshock and the mainshock events from a comparative analysis of p wave arrivals the series seems to be associated to different neighbouring seismogenic zones belonging to the crevillente system for the bullas 2002 and the bullas la paca series we found that it is unlikely that any of them have been triggered by the previous mula 1999 event but it appears that the main event in 2002 had an important influence on the triggering of its aftershock activity and the promotion of the mainshock and aftershock seismicity in the zone of the 2005 series summing the effects of the last two main events it may have been produced different zones of high stress increase on the aftershock area of the 2002 and 2005 series finally the seismicity of the two latest series could be associated to different neighbouring seismogenic zones

comment on a paper by zou et al 2017 entitled an integrated chemo and sequence stratigraphic framework of the early pennsylvanian deepwater outcrops near kirby arkansas usa and its implications on remnant basin tectonics