Confined Turbidite Systems

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Confined turbidite systems

SIMON A. LOMAS 1 & PHILIPPE JOSEPH 2

1Baker Atlas Geoscience, Stoneywood Park North, Aberdeen AB21 7EA, UK (e-mail." [email protected]) 2IFP School/Geology-Geochemistry Division, Institut Franfais du P~trole, 228-232, avenue Napoleon Bonaparte, 92852 Rueil Malmaison Cedex, France (e-mail." [email protected])

Abstract: Deep-water sedimentation is currently a major focus of both academic research and industrial interest. Recent studies have emphasized the fundamental influence of sea- floor topography on the growth and morphology of submarine 'fans': in many turbidite systems and turbidite hydrocarbon reservoirs, depositional system development has been moderately to strongly confined by pre-existing bounding slopes. This publication examines aspects of sediment dispersal and accumulation in deepwater systems where basin-floor topography has profoundly affected deposition, and the associated controls on hydrocarbon reservoir architecture and heterogeneity. The papers herein offer a global perspective which is wide-ranging in terms of both approach and location, including contrasting case studies of outcrop, subsurface, modern and experimental systems.

Confined turbidite systems are those deepwater are applied equally to process (ponded turbidity clastic depositional systems whose development current), depositional product (ponded turbidite) has been fundamentally constrained by pro- and basin/stratigraphic behaviour (ponded depo- nounced basin-floor topography. Many early centre). We favour the more general term con- conceptual and experimental models of turbidity finement to describe situations where sediment current deposition and submarine fan develop- gravity flows and their deposits are appreciably ment envisaged essentially unconfined radial affected by the presence of significant basin- development of lobe and fan-shaped deposi- floor topography, but without the connotation tional bodies. However, a wealth of case studies of complete containment. now available from many contrasting turbidite Closely associated with the concept of confined systems worldwide makes it clear that, in many deposition are the notions of flow reflection and basins, both sediment dispersal patterns and the deflection. In their study of ponded Quaternary geometries of depositional bodies have been pro- sediments in valleys on the flanks of the foundly affected by pre-existing or developing Mid-Atlantic Ridge, Van Andel & Komar (1969) basin-floor relief. It seems that perhaps most speculated that the rebound of turbidity currents large natural turbidity currents, particularly in off the bounding slopes was responsible for intracontinental basins, are not free to spread repeated grading profiles seen in their piston radially across a uniform basin floor. cores. Picketing & Hiscott (1985) recognized con- Van Andel & Komar (1969) used the term tainment of turbidity currents in the Cloridorme ponding to refer to a situation in which turbidity Formation (Ordovician of Qu6bec) from reversals currents of sufficiently large volume are fully of palaeocurrent indicators, which they inter- contained by an area of enclosed bathymetry. preted as the result of deflection and reflection of Similarly, Picketing & Hiscott (1985) used the part of large-volume turbidity currents from con- term contained turbidites to describe beds depos- fining slopes. Similar evidence of divergent palaeo- ited from turbidity currents that were confined flow indicators has subsequently been recognized within a basin too small to permit sustained at outcrop in various other successions represent- unidirectional flow. The terms ponding and, to a ing depositional systems where turbidity currents lesser extent, containment, are now generally have interacted with basin-bounding or intra- used to indicate a situation in which sediment basinal slopes (e.g. Kneller et al 1991; Smith, this gravity flows fill the floor of an enclosed depres- volume), and the likely effects of such interaction sion and are unable to surmount the bounding have been widely investigated through physical slopes (or 'sills') which bound that depositional experiments (e.g. Simpson 1987; Muck & Under- area ('mini-basin', 'silled sub-basin' or 'ponded wood 1990; Alexander & Morris 1994; Kneller depocentre'). Thus, essentially all of the sediment 1995; AI Ja'Aidi et al., this volume). carried into the depositional area by that flow will Implicit in the concept of confinement is the be trapped and deposited there. The same terms relationship of flow magnitude to size of

From: LOMAS, S. A. & JosEen, P. (eds) 2004. Confined Turbidite Systems. Geological Society, London, Special Publications, 222, 1-7. 0305-8719/04/$15.00 9The Geological Society of London 2004. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

2 S. A. LOMAS & P. JOSEPH depocentre. The general concept of flow efficiency in varied modern and ancient examples. The (e.g. Mutti 1979) is helpful here, describing a author emphasizes the contrasting behaviour flow's ability to deliver sediment, especially and architectural characteristics of coarse- sand, in a basinward direction. Thus, small grained/sand-rich and fine-grained/mud-rich volume, low-efficiency sediment gravity flows end-member systems but reminds us of the may behave in an effectively unconfined manner inadequacy of general models in capturing the even in small basins. Conversely, very large mag- variability of these real cases. The practical lim- nitude flows may interact with marginal confining itations of idealised models arise either from slopes even in large basins. Of course, if a con- emphasis on only one or two aspects or from fined depocentre is filled more quickly than the over-simplification (being too general to display topographic relief grows, the surface area of the architectural details). Bouma advocates the con- basin floor will increase with time. Hence, if struction of case-specific models based on a sediment supply characteristics remain similar, reconstruction of the specific natural controls successive depositional systems would be and their interactions in the generation and deliv- expected to :reflect progressively decreasing con- ery of sedimentary particles, the evolving basin finement. The reverse scenario could develop in configuration and processes of deposition and certain compressional settings. possible redeposition in that basin. In most of the studies detailed in this volume, Smith takes an alternative look at patterns of the origin of the confining topography is tectonic: sediment dispersal on topographically complex large-scale structural features, local fault scarps, slopes, distinguishing two conceptual end- folds or more subtle perturbations of basin-floor member systems, which he refers to as 'cascades gradients with associated tilting and faulting. In of silled sub-basins' and 'connected tortuous other instances, basin-floor relief is the result of corridors'. The first scenario is essentially a refine- slope collapse masses, halokinesis, mud diapirism ment of the 'fill-and-spill' model that emerged and, to a limited extent, differential compaction. from studies of the northern Gulf of Mexico The collection of papers hosted in this volume slope (e.g. Winker 1996; Prather et al 1998). In is not intended to provide an exhaustive treat- the 'connected tortuous corridors' scenario, ment of the subject of confined deepwater flows partly circumvent bathymetric obstacles, sedimentation, but rather to bring together a but follow a (laterally confined) continuous tortu- diverse assortment of approaches and observa- ous path down the slope. From two-dimensional tions which have a bearing on this topic. We sections, these two scenarios may be difficult to have ordered the contributions to reflect the distinguish (i.e. apparently separate sub-basins varying approaches of the researchers. Here may be directly connected out of the plane of we present an overview of those contributions section), although recognition of stratal onlap and the new perspectives they afford, and draw against a confining frontal slope should be diag- attention to promising channels (and lobes?) for nostic of the fill of a true silled sub-basin. future research. We are pleased that several of the systems described in the following papers are not widely known. It is hoped that the juxta- Experimental studies position of conceptual reviews, experimental work and case-studies of outcrop, subsurface Laboratory experiments have offered crucial and modern systems will stimulate new insights insights into the potential effects of basin-floor and connections and highlight key general ques- topography on sedimentation (e.g. Simpson tions which surmount the usual bounding slopes 1987; Kneller et al., 1991; Alexander & Morris of these scientific sub-communities. 1994). A! Ja'Aidi et al. outline a series of scaled experiments (using ballotini and silica flour to model sand and mud) to investigate how flow Overviews of confined turbidite systems volume, density and grain-size distribution affect the transport efficiency of turbidity cur- Two review papers introduce the broad-scale rents (i.e. their ability to carry 'sand' basinward) context of controls on, and patterns of, confined and the geometric characteristics of the resulting turbidite system development from contrasting deposits. In general, these experiments reaffirm viewpoints. intuitive expectations (cf. Mutti 1979; Mutti et al. Bouma sets the scene with an overview of the 1999): flow efficiency correlates directly with flow principal external controls on turbidite systems volume (which increases the initial potential (tectonics, climate, sedimentary characteristics energy and lessens the rate of velocity decrease and processes, and sea-level fluctuations), illus- due to gravitational spreading), sediment con- trating the interplay between these key controls centration (which increases the potential energy Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

CONFINED TURBIDITE SYSTEMS 3 of the flow, and hence the run-out distance), and active, uplifting margin, the dominant influences proportion of fine-grained material (which serves on depositional patterns appear to have been the to maintain overall negative buoyancy and also pre-existing basin-floor morphology, sediment decreases the settling velocity of the coarser frac- source characteristics and eustatic sea-level tion). When an arcuate obstacle was placed in the variations. path of the flows, the proportion of sediment Babonneau et al. describe a very different reaching the topographic obstruction, and the confined system from the deeply incised Zaire proportion of it able to surmount the topogra- submarine valley. They focus on a striking phy, increased as flow efficiency increased. The array of multiple terraces imaged along the most provocative outcome of these experiments inner flanks of the upper-fan valley, adjacent to concerns the influence of solids concentration the deeply incised sinuous thalweg. A range of on deposit geometry. With increasing initial possible origins for these confined terraces is flow densities, the resulting deposits generally evaluated (e.g. shallow-rooted faulting, chan- show an unsurprising trend of increasing length nel-wall slumping, repeated sedimentary infilling to width ratios (i.e. denser flows produce longer and incision, or levee aggradation). Morpho- and thinner deposits). However, above a certain logical analysis and seismic character favour an density threshold (c. 13% initial sediment con- interpretation of these remarkable features as centration by mass), the deposits of successively levees, confined within the incised valley. Many denser flows tend to show decreasing length-to- terraces correspond to the infill of abandoned width ratios. The authors interpret this intriguing meander loops, and are believed to record result in terms of inhibition of turbulence at high aggradation of relatively dilute turbidite current concentrations. deposits associated with spiilover and flow- stripping processes. Terrace initiation appears to correspond to phases of vertical incision of the Modern turbidite systems thalweg, occurring concurrently with meander migration. Shallow penetration geological and geophysical data from modern turbidite systems offer the clearest perspective on the morphology and plan- Outcrop case studies form arrangement of the components ofturbidite depositional systems. Two detailed studies of The remainder of this volume is devoted to a contrasting modern systems are presented here contrasting collection of outcrop-based case that document remarkable datasets. studies, many focusing on the disproportionately Gervais et al. describe the modern sandy Golo numerous Eocene-Oligocene-Miocene turbidite turbidite system, developed in a partly confined basin-fills exposed around the world. setting on the eastern margin of Corsica. The In a large-scale investigation of Oligocene- upper Quaternary deepwater deposits have Miocene turbidite wedges exposed in the North- been imaged using a closely spaced grid of ern Apennines, Cibin et aL find a repeated tri- sparker seismic-reflection profiles, covering a partite stacking motif involving an upward total survey length of some 1000km. These transition from thick-bedded, sandstone-rich high-resolution data give a 2 m vertical resolu- units ('depocentre stage'), into thin-bedded tion of a turbidite system composed of four mudstone-rich units, and ultimately grading up non-coalescent fans characterized by stacked to mudstone-dominated units ('abandonment depositional bodies. Canyon, gully, sandy chan- stage'). This rhythm is interpreted in terms of a nel, muddy levee, and sandy lobe architectural sediment input signal: the abrupt 'switching on elements are identified on this high-resolution and off' of coarse-grained input. Biostrati- dataset at a scale which should allow direct graphic data allow discrimination of regional comparison with outcrop examples. Each of the effects (overall decrease in sediment input) from four fans appears to have been fed by a separate intrabasinal changes in sediment dispersal (i.e. canyon, ultimately linked up-dip to a single depocentre migration resulting in the 'switch- fluvio-deltaic point-source; the canyons were ing-off' of one turbidite system as a new system apparently active simultaneously. Structural is 'switched-on' basinward). Thus, Cibin et al. confinement of the system as a whole has led to are able to recognize distinct pulses driven by a predominance of aggradation, and smaller- hinterland tectonics (Chattian; Middle Burdiga- scale slope variations have constrained the lian), and to distinguish these from episodes of specific morphology and architecture of deposi- depocentre-shift related to basin reorganization tional lobes. Interestingly, it seems that, notwith- (Chattian, Langhian), and from phases of dimin- standing the setting adjacent to a tectonically ished regional sediment supply (Late Aquitanian, Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

4 S. A. LOMAS & P. JOSEPH

Middle Burdigalian, Early Serravallian), perhaps basin-floor aggradational phase of clinoform driven by elevated sea levels. growth, whereas later development of the same Hodgson & Haughton detail the interplay clinoform involves a phase of shelf-margin accre- between deepwater sedimentation and syn- tion. The component sandbodies each display an depositional faulting in the Neogene fill of the upward increase in bed thickness, involving a Tabernas-Sorbas Basin, SE Spain, documenting transition from predominantly thin-bedded, the effects of a fault which appears to have pro- sheet-like ripple- to parallel-laminated turbidites pagated through to the sea-bed during turbidite (interpreted as channel-mouth lobes, sandy deposition. The E1 Cautivo Fault is an oblique levees and crevasse splays) upwards into thickly strike-slip fault that accommodated an area of bedded, erosive-based, parallel-laminated and deeper ponded bathymetry (a 'mini-basin') on structureless sandstones (interpreted as con- its southern flank. The sea-bed expression of structional channel-fills). Flows reaching the this fault varied between a blind fold, associated basin floor were apparently deflected laterally with local wedging and onlap of stratigraphy, by anticlinal sea-floor topography, resulting in and an unstable fault scarp with local collapse restricted basinward extent and longitudinal features. Its influence on sedimentation is appar- palaeocurrent indicators in the youngest fan ent in terms of both sediment dispersal (sea-floor sandbodies. warping associated with the fault trace largely The Ordovician-Silurian fill of the Welsh determined the flow paths of incident turbidity Basin contains a diverse range of deepwater currents) and stratigraphic growth (evolving depositional systems that record the influence patterns of thickness variations associated with of basin-floor topography on sediment distribu- changing rates of differential subsidence across tion patterns. Smith synthesizes extensive data- the fault). Characteristic sedimentation in the sets to describe the evolution of these successive fault-controlled ponded depocentre involved turbidite systems in the context of evolving distinctive thick sheet-like sandstone-mudstone topographic controls. An initial base-of-slope couplets, interpreted as the deposits of large- system became overstepped by a channel-fed volume turbidity currents that were entirely con- lobe system once the inboard accommodation fined within the structurally defined mini-basin. space became filled. All systems exhibit evidence Esehard et al. analyse architectural relation- that flows were deflected into near-parallelism ships in the remarkable large-scale exposures of with the tectonically generated regional slopes. the Maastrichtian Pab Sandstone in Pakistan. Parts of these systems are also characterised by The successions they describe record initial large azimuthal disparities between the trends hinterland uplift with shelf erosion, canyon of sole structures and ripple cross-laminae, incision, and the development of an extensive which is regarded as direct sedimentological evi- high-efficiency basin-floor fan dominated by dence of partial flow reflection from containing channel complexes. During subsequent trans- slopes. A forward geometric model is used to gression, a more restricted turbidite system evaluate plausible stratal architectures in relation developed on the slope, consisting of proximal to the main bounding slope. Smith also cham- conglomeratic channel fills, aggradational 'mid- pions the analogue value of lessons learned fan' channel fills and tabular lobe deposits. In from this less fashionable outcrop system to contrast to the older basin-floor fan, this slope subsurface prediction. fan testifies to reduced flow transport efficiencies, Zink & Norris describe stacking patterns in the and hence less confinement (fewer flows reaching Tertiary fill of two small fault-bounded basins, the bounding slopes) and less systematic internal the Te Anau and Waiau basins, of southwest organization. The evolution in depositional pro- New Zealand. These basins, initially extensional cesses and architectural styles seems to have been but subsequently dominated by strike-slip tec- driven by a general change in slope morphology, tonics, were only a few tens of kilometres wide from an initially well-defined shelf-slope break to yet each accumulated sedimentary successions a smoother, lower-angle ramp profile developed 6-8km thick before undergoing transpressive through slope progradation. inversion in late/post-Miocene times. Marked Crabaugh & Steel describe architectural and lateral and vertical changes in facies are charac- facies relationships between shelf-slope clino- terised, but, despite their limited lateral extent, forms and basin-floor fan sandstone bodies these basins developed a full range of sedi- from extensive and beautiful exposures of mentary facies and architectural elements, with Eocene successions in the Central Tertiary pronounced proximal to distal transitions. Basin of western Spitsbergen. Where clinoforms Satur et al. describe the proximal, channelized are sand-prone they include a deepwater sand section of a topographically constrained deep- complex: submarine fans represent an early, water fan in the Miocene Adana Basin of Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

CONFINED TURBIDITE SYSTEMS 5 southern Turkey. Their study documents basin- all measured sections, with systematic spatial ward facies changes along a 10km transect variations in the degree of clustering, such that within one of four fan-feeder channels. A well different parts of the basin are characterized by defined down-channel transition is observed different Hurst statistics. The statistical clustering from proximal, ungraded disorganized conglom- is associated with lateral and vertical facies erates to more organized, inverse-to-normal and variations in turn related to depositional sub- normally graded conglomerates. Concomitantly, environments within the Castagnola Basin. bedding style changes from scour-based, sheet- Although the origins of this clustering are not like units up-dip into a complex of small channels fully constrained in terms of primary sedimentary and bar-forms mid-way along the transect, into processes, this type of analysis highlights the thick-bedded, structureless facies further down- potential for semi-deterministic predictions of current. Channel gradients can be tentatively facies away from sample points in systems which reconstructed and changes in channel gradient are locally well characterized. are considered to constitute a key control on Conybeare et aL detail an approach to geo- the hydrodynamics within the gravity flows, cellular modelling of turbidite systems. Their and thus on the resulting stratal patterns. case study is the Eocene Hamitabat Formation, Cornamusini describes the sedimentary organi- which forms an important gas reservoir in the zation of the Oligocene 'Macigno Costiero' large fault-bounded Thrace Basin of north- siliciclastic turbidites exposed in coastal Tus- western Turkey, adjacent to the North Anatolian cany. These are the remnants of a sand-rich, Fault System. The main reservoir comprises low-efficiency turbidite system developed within gravity flow sandstones sourced from fluvio- a partially confined setting in the Northern deltaic systems to the north and northeast. Apennines foreland basin system. The system Correlation, based mainly on upward-fining comprises unchannelized and channelized sheet cyclical successions, indicates lobate depositional sandstone bodies, a main channel-fill unit, geometries and subtle topographic control on together with distributary channel-fills, overbank sediment dispersal (compensation). Construction and channel margin deposits. Stacking patterns of the stratigraphic framework for the 3D geo- indicate five stages of depositional system devel- cellular reservoir model of the field relied heavily opment. The development of sheet (lobe) stages on the correlation of depositional cycles. A is characterized by negative vertical trends mathematical approach to correlation was (upward coarsening/thickening), which can be adopted, employing frequency and difference interpreted as a retrogressive transition from spectra to characterize cyclicity in wireline log distal lobe to proximal lobe up to a channel- curves. The model itself was populated with lobe transition zone. facies objects whose dimensions were based on analogue data together with direct knowledge of the depositional systems. Upscaling of the Quantitative characterization of static geological model and fluid-flow simulation turbidite systems allowed comparison with the actual production history and hence refinement of the model. Two final studies address different issues of quan- Although the resulting model is very much a titative characterization of turbidite systems. pragmatic rather than a scientifically-driven This is an area of increasing significance given realization, the modelling process does afford the growing economic importance of deepwater new insights into the range of possible geometries hydrocarbon reserves, and the corresponding of the sedimentary systems. predictive and modelling needs of the industry. Felletti uses quantitative outcrop data from the Castagnola Formation in the Tertiary Closing remarks Piedmont Basin of NW Italy to investigate the potential of geostatistical tools for discrimi- The range of studies presented here reaffirms the nation of depositional sub-environments in a diversity ofdeepwater clastic systems, but suggests confined turbidite system. Three variables were a broad consensus that overriding controls on studied: thickness of sandstone and siltstone stratal patterns and architecture are sediment beds, a grain-size index, and sand and silt thick- supply character and slope gradients in the receiv- ness percentage (i.e. the ratio of coarse division ing basin. In particular, flow volume and efficiency to overlying mudstones). Felletti applies statis- relative to the scale of the depocentre may largely tical tests (the Hurst tests) to assess vertical determine the character and distribution of the and lateral distributions of these variables. deposit. A related point emphasized here is Significant clustering is found to occur in ahnost the appreciation of the three-dimensionality of Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

6 S. A. LOMAS & P. JOSEPH sediment dispersal pathways in confined systems. fresh insights into the behaviour of variably con- Future studies on sediment supply and gravity fined flows. A new emphasis here may be attempts flow initiation processes will be strongly influenced to simulate erosion beneath large sediment gravity by the emerging importance of hyperpycnal flow flows: bed contacts in many sand-rich confined as a likely major supply mechanism (e.g. Mulder systems show evidence of substantial erosion, & Syvitiski 1995), which will require development but the mechanics of this erosion, and the result- of new depositional models. ing geometries and their implications (e.g. for More generally, the case studies compiled flow transformations and for reservoir connectiv- here highlight the continuing importance of ity), have been little studied to date. Integration of outcrop-derived datasets in providing ground- experimental work with outcrop studies targeted truth detail to constrain conceptual models. A to test developing hypotheses of sediment gravity critical impetus behind acquisition of detailed flow processes may enhance the extent to which outcrop datasets has been the requirement of flow properties and efficiency be deduced from the hydrocarbon industry for generic and numer- deposit characteristics. ical constraints on correlation and modelling of deep-water reservoirs. In turn, geocellular and We are grateful to Vincent Hilton and Jonathan Turner layered 3D geological models are now offering for constructive comments on the first draft of this insight and constraints on sedimentary archi- paper. tectures and evolution. In reaching for outcrop analogues to help understand the architecture and heterogeneity of turbidite reservoirs, References industry geoscientists have focused heavily on a surprisingly small number of outcrop favourites ALEXANDER, J. & MORRIS, S. 1994. Observations on experimental, nonchannelized, high-concentration (the 'top ten' is perhaps: Ainsa, Annot, Brushy turbidity currents and variations in deposits Canyon, Cerro Torro, Jackfork, Karoo, Mar- around obstacles. Journal of Sedimentary Research, noso-Arenacea, Mt Messenger, Ross, Tabernas). Section A: Sedimentary Petrology and Processes, 64, Although all of these systems certainly still have 899-909. a great deal to teach us, it is to be hoped that KNELLER, B. C. 1995. Beyond the turbidite paradigm: compilations such as this volume will help to physical models for deposition of turbidites and raise the profile of the many other informative their implications for reservoir prediction. In: systems available. HARTLEY, A. & PROSSER, D. J. (eds) Characterisa- Previous authors have noted the difficulties of tion of Deep Marine Clastic Systems, Geological reconciling interpretations of modern and Society, London, Special Publications, 94, 2946. KNEELER, B. C., El)WARDS, D., MCCAEFREY, W. ~:; ancient turbidite systems (e.g. Normark et al. MOORE, R. 1991. Oblique reflection of turbidity 1993), which arise partly from the limitations currents. Geology, 19, 250 252. of the Holocene sea-level regime but more funda- MucK, M. T. & UNDERWOOD, M. B. 1990. Upslope mentally from the differences in scale and resolu- flow of turbidity currents: a comparison among tion of outcrop, subsurface and marine data. field observations, theory and laboratory experi- Several contributions here indicate encouraging ments. Geology, 18, 54-57. convergence in recent years between outcrop, MULDER, T. & SYVITSKI, J. P. M. 1995. Turbidity subsurface, modern and also experimental currents generated at river mouths during excep- results. Integration of modern datasets (which tional discharges to the world oceans. Journal of Geology, 103, 285-299. image morphology and spatial distribution) MuTTI, E. 1979. Turbidites et cones sous-marins with appropriate outcrop data (giving the profonds. In." HOMEWOOD, P. (ed.) Sedimentation internal character and vertical organization) is detritique (.fluvial, littoral et marine). Institut de perhaps one underexploited avenue for research. G6ologie, Universit6 de Fribourg, Suisse, 353-419. The inherent variability of these sedimentary MUTTI, E., TINTERR1, R., REMACHA, E., MAVILLA, N., systems ensures that a unified deterministic under- ANGELLA, S. & FAVA, L. 1999. An Introduction standing of their development remains elusive, to the Analysis of Ancient Turbidite Basins from and hence our ability to determine geometries an Outcrop Perspective. AA PG Continuing Educa- and facies away from sample points remains lim- tion Course Note Series, 39. ited. Central to furthering this predictive capacity NORMARK, W. R., POSAMENTIER, H. & MUTTI, E. 1993. Turbidite systems: state of the art and future will be an improvement in understanding of flow directions. Reviews of Geophysics, 31, 91-116. and depositional processes at real scale: large PICKERING, K. T. & HISCOTT, R. N. 1985. Contained natural sediment gravity flows remain difficult to (reflected) turbidity currents from the Middle observe or model, but major progress with the Ordovician Cloridorme Formation, Quebec, design of physical experiments with particulate Canada: an alternative to the antidune hypothesis. materials offers an obvious (if difficult) route to Sedimentology, 32, 373-394. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

CONFINED TURBIDITE SYSTEMS 7

PRATHER, B. E., BOOTH, J. R., STEFFENS, G. S. & CRAIG, VAN ANDEL, TJ. H. & KOMAR, P. D. 1969. Ponded P. A. 1998. Classification, lithologic calibration, sediments of the Mid-Atlantic Ridge between 22 ~ and stratigraphic succession of seismic facies of and 23 ~ North latitude. Geological Society of intraslope basins, deep-water Gulf of Mexico. America Bulletin, 80, 1163-1190. AAPG Bulletin, 82, 701 728. WINKER, C. D. 1996. High-resolution seismic stratigra- SIMPSON, J. E. 1987. Gravity Currents in the Environ- phy of a late Pleistocene submarine fan ponded by ment and the Laboratory. Cambridge University salt-withdrawal mini-basins on the Gulf of Mexico Press, 24pp. continental slope. Offshore Technology Conference Proceedings, 619-628.