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This study offers new insights into the internal architecture of shallow marine carbonate sediments deposited in an epeiric sea formed on a broadly flooded passive margin continental shelf. The Ullayah Member of the Late Jurassic Hanifa Formation is exposed along the Tuwaiq Mountain Escarpment in Central Saudi Arabia and serves as an example. High‐resolution drone imagery over a 4 × 4 km2 wadi system, measured‐sections and thin‐section petrography are utilized to develop the three‐dimensional architecture of the lagoonal sediments deposited in an inner‐ramp setting. Parasequence sets have been mapped on the digital outcrop models that demonstrate a high degree of lateral and vertical thickness variability associated with stromatoporoid/coral buildups and inter‐buildup sediments. The stromatoporoid/coral buildups have been interpreted to be deposited during the late Transgressive Systems Tract and Highstand System Tract. The positive relief developed by the stromatoporoid/coral buildups resulted in hydrodynamic acceleration of currents in the inter‐buildup areas, which limited sediment deposition. The incomplete filling of the inter‐buildup areas led to an undulating topography, which significantly influenced depositional architecture in the next parasequence set. This theme of sediment filling, also referred to as compensational stacking, was repeated over the next two parasequence sets, with an overall decreasing accommodation towards the late highstand, eventually levelling the uneven topography at the top of the Ullayah Member. The study offers insights into the processes of sediment accumulation in an inner ramp lagoon and/or on a flat‐top shallow marine epeiric carbonate shelf. Although accumulation is cyclic, neither strict facies patterns nor uniform cycle thicknesses can be discerned on a kilometre scale. This insight potentially provides a reason for the frequently debated correlation of cycles and facies patterns in carbonate sequences in shallow epeiric seas. [ABSTRACT FROM AUTHOR]

Abstract This study aims to interpret and document the depositional architecture styles and sequence stratigraphic framework of the Ash Shumaysi Formation in the Jeddah‐Makkah region, the west‐central part of Saudi Arabia, and presents an example of rarely discussed, local‐scale sub‐basins (half grabens). It also shows the relationships between synchronous sedimentary processes and pre, syn and post‐rift conditions. The described lithofacies and their facies associations indicate the presence of seven architectural depositional styles: proximal‐distal braided fluvial, meandering fluvial (point bar), crevasse splay, floodplain, estuarine and lacustrine. A proposed depositional model for the Ash Shumaysi Formation is drawn. The Ash Shumaysi Formation forms a second order depositional sequence, which is organised into two third order depositional sequences (sequences I and II) bounded by three sequence boundaries. Each third‐order sequence encloses the low accommodation systems tract and high accommodation systems tract. The low accommodation systems tract represents the coarse‐grained, braided‐distal fluvial facies developed during low accommodation space associated with high sediment supply (high discharge). The high accommodation systems tract encloses the fine‐grained deposits of point bar, estuarine and lacustrine facies that reflect the creation of significant accommodation space and low sediment supply (low discharge). Vertical and lateral variations of the inferred depositional architectural styles, sequences and systems tracts reflect that tectonic forces and climate are the main controlling factors during deposition of the Ash Shumaysi Formation, although base‐level changes in response to sea‐level changes cannot be ruled out.

This study aims to interpret and document the depositional architecture styles and sequence stratigraphic framework of the Ash Shumaysi Formation in the Jeddah‐Makkah region, the west‐central part of Saudi Arabia, and presents an example of rarely discussed, local‐scale sub‐basins (half grabens). It also shows the relationships between synchronous sedimentary processes and pre, syn and post‐rift conditions. The described lithofacies and their facies associations indicate the presence of seven architectural depositional styles: proximal‐distal braided fluvial, meandering fluvial (point bar), crevasse splay, floodplain, estuarine and lacustrine. A proposed depositional model for the Ash Shumaysi Formation is drawn. The Ash Shumaysi Formation forms a second order depositional sequence, which is organised into two third order depositional sequences (sequences I and II) bounded by three sequence boundaries. Each third‐order sequence encloses the low accommodation systems tract and high accommodation systems tract. The low accommodation systems tract represents the coarse‐grained, braided‐distal fluvial facies developed during low accommodation space associated with high sediment supply (high discharge). The high accommodation systems tract encloses the fine‐grained deposits of point bar, estuarine and lacustrine facies that reflect the creation of significant accommodation space and low sediment supply (low discharge). Vertical and lateral variations of the inferred depositional architectural styles, sequences and systems tracts reflect that tectonic forces and climate are the main controlling factors during deposition of the Ash Shumaysi Formation, although base‐level changes in response to sea‐level changes cannot be ruled out. [ABSTRACT FROM AUTHOR]

Turbidites have been regarded as an important sedimentary infilling component in both oceans and lakes, but limited studies have been performed on the mechanisms governing the initiation and development of lacustrine turbidite systems. The present study offers unique insight into the controls and potential extent of ancient lacustrine turbidite systems by an investigation of the Triassic Ordos Lake, where a large turbidite system had been traced across >25 653 km2. This article shows by comparison that the Triassic Ordos Lake turbidite system is larger than all known modern and ancient lacustrine counterparts. The exceptionally large intracontinental sag basin provided a relatively unconfined environment for the development of the turbidite system, explaining its vast extent. Extraordinary flood events formed during the Carnian Pluvial Episode facilitated continuous sediment supply into the turbidite system, supporting its accumulation. Lacustrine flood‐related turbidity currents travelled as sediment‐laden turbulent flows, showing an increase in the proportion of suspended‐load deposits and a decrease in the proportion of bed‐load deposits downstream from the river mouth. Five architectural elements have been revealed, reflecting a distinctive assemblage of erosional bedforms and depositional bedforms in channel‐lobe systems, and their recognition criteria were established. This study changes the traditional understanding of lacustrine turbidite systems, generally interpreted as having smaller sizes, and demonstrates likewise in the lacustrine realm, that extreme flood events can generate a world‐class deep‐water turbidite system, which can even be comparable with its submarine counterparts. This study also confirms that the combination of low‐gradient slopes and a long‐lived, mixed‐load, prograding fluvial feeder system can produce exceptionally large‐scale deep‐lake flood‐related turbidites. Furthermore, it has implications for the prediction of facies and reservoir quality in ancient lacustrine turbidite systems. [ABSTRACT FROM AUTHOR]

We present a series of 2D thermo-mechanical numerical experiments of thick-skinned crustal extension including a pre-rift salt horizon and subsequent thin-, thick-skinned, or mixed styles of convergence accompanied by surface processes. Extension localization along steep basement faults produces half-graben structures and leads to variations in the original distribution of pre-rift salt. Thick-skinned extension rate and salt rheology control hanging wall accommodation space as well as the locus and timing of minibasin grounding. Upon shortening, extension-related basement steps hinder forward propagation of evolving shallow thrust systems; conversely, if full basin inversion takes place along every individual fault, the regional salt layer is placed back to its pre-extensional configuration, constituting a regionally continuous décollement. Continued shortening and basement involvement deform the shallow fold-thrust structures and locally breaches the shallow décollement. We aim at obtaining a series of structural, stratigraphic and kinematic templates of fold-and-thrust belts involving rift basins with an intervening pre-rift salt horizon. Numerical results are compared to natural cases of salt-related inversion tectonics to better understand their structural evolution.

Structural and stratigraphic geometries in the Central Indus Basin of Pakistan are subjects of interest for explorers. The thickening and thinning sequences in conjunction with structural anomalies often provide an environment for hydrocarbon accumulation. Hydrocarbons play a vital role in the energy mix of Pakistan. With the help of well correlation, work on seismicity can be confirmed by marking terminations, depositional extent and thickness variation at different stratigraphic levels. Therefore, this work presents depositional geometries of Eocene and Cretaceous reservoirs [Sui Main Limestone (SML) and B-sand interval of Lower Goru Formation], keeping in view the vertical and lateral resolution of the seismic data and the distance between the wells for correlation. The Eocene SML and Cretaceous B-sand are extensively mapped as isochrones using 20 seismic lines and correlated with ten wells. The results give evidence of a building up of shallow marine shelf carbonate in Eocene SML. The isochrone maps also indicate that Eocene SML has untapped potential east of the study area. The Cretaceous B-sand demonstrates sheet-like geometry of sand-filled delta progrades in the west to southwest direction in a ramp setting. This geometry suggests an updip hydrocarbon potential in Cretaceous B-sand reservoir in the north of the study area. Because of the pinching out behavior and excellent stratigraphic trapping system, these two reservoirs can be considered future exploration targets. [ABSTRACT FROM AUTHOR]

This dataset comprises the detailed descriptions and laboratory measurements of sediment profiles from the semi-arid environs of the Pre-Pottery Neolithic site Göbekli Tepe in southeastern Turkey—one of the oldest monumental structures of humankind dating to c. 11.5–10 ka BP. Focus of the descriptions are the architectural elements of the deposits allowing to conduct facies interpretations and the reconstruction of different depositional environments. This is supported by bulk geochemical sediment analyses (pH, electrical conductivity, magnetic susceptibility, and loss on ignition) and the determination of total and inorganic carbon contents and chemical element concentrations. The Late Holocene chronology is based on radiocarbon dating of charcoal pieces and bulk samples containing organic matter from buried organic-rich topsoil horizons and soil sediments. Lithic artifacts from the Pre-Pottery Neolithic provide additional age estimates. Nykamp et al. [1] provide the synthesis that is based on the presented datasets.

The upper portion of the Cuyo Group in the Zapala region, south‐eastern Neuquén Basin (Western Argentina), encompasses marine and transitional deposits (Lajas Formation) overlain by alluvial rocks (Challacó Formation). The Challacó Formation is covered by the Mendoza Group above a second‐order sequence boundary. The present study presents the stratigraphic framework and palaeophysiographic evolution of this Bajocian to Eo‐Calovian interval. The studied succession comprises the following genetic facies associations: (i) offshore and lower shoreface–offshore transition; (ii) lower shoreface; (iii) upper shoreface; iv) intertidal–subtidal; (v) supratidal–intertidal; (vi) braided fluvial to delta plain; (vii) meandering river; and (viii) braided river. The stratigraphic framework embraces four third‐order depositional sequences (C1 to C4) whose boundaries are characterized by the abrupt superposition of proximal over distal facies associations. Sequences C1 to C3 comprise mostly littoral deposits and display well‐defined, small‐scale transgressive–regressive cycles associated with fourth‐order depositional sequences. Such high‐frequency cycles are usually bounded by ravinement surfaces associated with transgressive lags. At last, the depositional sequence C4 delineates an important tectonic reorganization probably associated with an uplift of the Huincul Ridge. This is suggested by an inversion of the transport trend, north‐westward during the deposition of C1 to C3 depositional sequences (Lajas Formation) to a south‐west trend during the deposition of the braided fluvial strata related to the C4 depositional sequence (Challacó Formation). [ABSTRACT FROM AUTHOR]

Abstract Accommodation rates in rift basins are mainly controlled by tectonics. However, during early rift stages, normal fault activity is dispersed and incipient, which makes it difficult to recognize the effects of early crustal extension. The sedimentary stacking pattern of rift-related depositional environments can be decisive to address this question. This paper aimed to evaluate the stratigraphic record of the Tithonian-Berriasian (?) Serraria Formation (Sergipe-Alagoas Basin, Brazil), which was deposited in the Afro-Brazilian Depression, as a result of the early extension of West Gondwana. In total, 14 lithofacies were described, interpreted and arranged into 7 facies associations. At the base of the formation, bars and sand sheets were deposited by low discharge braided channels, which were deposited on top of lacustrine mudstones of the Bananeiras Formation. There is a change in stratigraphic architecture in the middle of the section, where fluvial channels become deeper due to increasing discharge, promoting an increase in grain size of the transported bedload and greater rates of coarse sand and gravel bar stacking. Rare crevasse channels and restricted aeolian dune fields occur adjacent to braided channel belts. Upwards, the Serraria Formation becomes dominated by delta front and delta plain deposits. The fluvial and aeolian facies associations represent a progressive decrease in accommodation, while the upper fluvio-deltaic interval means an increase in accommodation, pointing to the early rift stage climax. The fluvial "Caioba" sandstone on top of the Serraria Formation indicates reestablishment of fluvial drainage either due to decreasing tectonism or due to low accommodation at the time of deposition. Thus, the sedimentary stacking pattern of Serraria Formation represents higher frequency cycles within an early rift tectonic system tract. [ABSTRACT FROM AUTHOR]

Abstract Sub-seismic sand-body characterization depends largely on understanding the heterogeneities observed in outcrops of equivalent depositional settings to subsurface reservoirs (reservoir analogs). Outcrop information, however, rarely covers the whole depositional system. Ground-penetrating radar (GPR), on the other hand, is a powerful tool for the high-resolution visualization of sand-rich deposits in the shallow subsurface, allowing for the description of their internal architecture, relationships with depositional systems, and its larger scale stratigraphic evolution. The internal character of radar patterns can be interpreted with respect to facies seen in exposures, leading to the prediction of heterogeneities below radar resolution. In this paper we use GPR and outcrops to describe the heterogeneity of Quaternary coastal-plain deposits from central Santos Basin (Paraná state, southern Brazil) where Pleistocene and Holocene, wave-dominated regressive barriers and transgressive lagoons and estuaries were formed under the influence of Quaternary sea level and climatic changes. Sedimentary facies reveal the predominance of sand deposited under the influence of tidal processes, fair-weather and storm wave processes. Radarfacies indicate a tendency of progradation of beach-face reflectors over subtidal radarfacies within two regressive successions separated by a regional unconformity. Interpretation of GPR resulted in the definition of 13 radarfacies arranged in three associations reflecting major depositional systems: (1) strandplains formed by prograding beach/dune-ridge sets over subtidal deposits, (2) spit-inlets, with progradation of beach faces over subtidal deposits and longshore accretion of spits, and (3) paleolagoons/paleoestuaries. Sedimentary facies indicate that strandplains and spit-inlets are predominantly sandy, while a muddy composition is expected in paleolagoons/paleoestuaries. The distribution and evolution of these systems were controlled by base-level oscillations and/or sediment supply that resulted in the formation of two regressive barriers separated by a wave ravinement surface configuring two parasequences with a wide variety of inter- and intra-sand body heterogeneities. This arrangement imprints a relatively high degree of compartmentalization within deposits that are traditionally considered continuous and homogeneous. Therefore, the Quaternary coastal plain of Paraná can be used as an analog for compartmentalized coastal reservoirs. [ABSTRACT FROM AUTHOR]

Abstract Degree of confinement refers to the degree to which sediment gravity flows are influenced by the surrounding basin relief and interact with the basin margins, and is a key controlling factor in determining the depositional architectures of turbidite sheet systems. Two well exposed late Palaeozoic sandy turbidite sheet systems in the Paganzo Basin at Cerro Bola, north-west Argentina, termed Stages II and IV (unconfined and highly confined respectively), provide three-dimensional constraints on facies associations, stacking patterns, depositional geometries and evolution of these turbidite sheet systems. Cluster analysis has been applied to define facies associations in these two systems at an appropriate hierarchical level depending on the overall nature of the system. The overlap index (OI), OI = A 0 /A 1 , where A 0 is the overlap area and A 1 is the area of underlying depositional element, is adopted to quantitatively characterise the stacking patterns. The two turbidite sheet systems show contrasts in that: (1) Stage II is built up by four hierarchical elements, each stacked in a shingled or compensational way with the majority of overlap index values of 0.7 and 0.8, to form higher hierarchical elements, whereas in Stage IV, individual beds stack vertically with OI = 1, together forming the stage and (2) Four facies associations have been identified in Stage II by cluster analysis and they occur in a spatial sequence from axis to fringe; one facies association has been identified in Stage IV and it shows little variation spatially across the basin. In unconfined systems, depositional elements are self-organized, and autocyclic controls are dominant, whereas in highly confined systems, confinement has suppressed the autocyclic signal and systems are allocyclically controlled. [ABSTRACT FROM AUTHOR]

Inner shelf to shelf-margin delta and slope-fan deposits in the Cenozoic Pearl River Mouth Basin in the northern continental margin of the South China Sea comprise the most important petroleum reservoirs in the basin and their evolution reflects a changing interplay of tectonics, sea level change and sediment supply. Integrated analysis of 3D seismic, well logs and core data allows interpretation of depositional architecture and evolution of the delta systems as they responded to the major controls. Inner shelf-delta systems, sited on the landward reaches of the continental margin, are characterized by thickly stacked distributary channel, thin (20-40 m) but relatively coarse delta-front and thin, fine-grained, distal delta to prodelta deposits. In contrast, outer shelf to shelf-margin deltaic systems formed 200 m (merging outwards to 1000 m) high clinoforms with steep slopes imaged on 3D seismic profiles as S-shape or tangential progradational reflections. Slumps and debris flow as well as sandy turbidite slope-fan deposits are common on the slopes of the clinoforms. Basinward and landward, cross-shelf transits of the delta systems are evident, as they formed some 18–20 stacked, high-frequency transgressive-regressive deltaic cycles (0.8–3 Myr) and five megacycles (3 to 10 Myr). Development of the deltaic cycles is interpreted as the result of high-amplitude sea level falls and rises related to glacio-eustasy as well as to changing sediment supply. The large-scale transgressive-regressive evolution of the deltaic clastic wedge is likely to have been controlled mainly by long-term changes in tectonic subsidence rate and sediment supply. The shelf-edge deltaic regressions are likely to have developed during sea level fall, but also during periods of high sediment input enhanced by uplifted tectonic relief and catchment enlargement or at times by monsoonal intensification events. [ABSTRACT FROM AUTHOR]

The Jimusaer oil shale (JOS) of the Upper Permian Lucaogou Formation in the southeastern margin of the Junggar Basin, Northwest China has retained a close relationship with the Bogda orogeny. JOS samples were studied for organic geochemistry, and samples of other rocks collected from between the oil shale layers (sandstone, mudstone shale, dolostone, limestone) were investigated for mineral characteristics. The results showed JOS samples to have a high total organic carbon (TOC) content, 5.35-21.45%, and a high oil yield, 3.67-10.3%. Dolomite, clay minerals, quartz, tuffaceous matrix, tuff debris, calcite, ferruginous debris, siliceous debris and anorthose could be found in the samples of other rocks. The Jimusaer oil shale was characterized by fine grain size, dark color and horizontal bedding. Depositional architecture and symbiotic rocks indicated that JOS was mainly deposited in a semi-deep to deep water environment under reducing conditions. The oil shale developed in the highstand systems tract (HST) and was enriched in organic matter. [ABSTRACT FROM AUTHOR]

Submarine fan architecture has long been considered much complicated as controlled by both allogenic and autogenic mechanisms. However, to which extent the allogenic sea-level change controls the submarine fan architecture is still unclear. This study uses integrated 3-D seismic, well-log and core data to characterize the submarine fan architecture in a deepwater sequence of the Niger delta basin. Correlation of the timing of architecture units to high-frequency sea-level curve helps to investigate the sea-level control on architecture distribution and evolution of submarine fan systems. The studied sequence is a 3rd-order sequence that formed during 12.5–10.5 Ma and contains a lowstand systems tract (LST) and a transgressive-highstand systems tract (TST-HST). We find that the LST develops a single channel system that is terminated by a lobe system; whereas the TST-HST develops two mutually incised channel systems and mudflow deposits, which are distinct from the conventional condensed sections and interpreted to result from the repeated 4th-order sea-level cycles during the TST-HST of the 3rd-order sequence. Single submarine fan systems, which last for ∼0.3–0.6 Myr, are assumed to form in response to single 4th-order sea-level cycles since they are well correlated with each other. Each single submarine fan system contains several vertically stacked complex sets, which are well correlated with 5th-order sea-level cycles that last for ∼0.1–0.2 Myr, suggesting their potential genetic links. Different complex sets in a single submarine fan system exhibit variable architectural features, which are interpreted to result from the evolution of gravity-flow types as the 4th-order sea-level fluctuates. Thus for the Niger system, at time scales >0.1 Myr, the allogenic sea-level change is considered to have played a major role in controlling the submarine fan architecture at the scale of submarine fan systems and complex sets, whereas autogenic effects on the submarine fan architecture may increase and become dominant on time scales <0.1 Myr. [ABSTRACT FROM AUTHOR]

Middle Pleistocene Gilbert-type delta in the Gulf of Corinth, Greece, has been investigated combining field methods and photo acquisition by drone to generate a high-resolution 3D model. This study case can be used to document four different dynamics in Gilbert-type bottomset deposits, each one of which is characterized by a specific range of facies, facies associations and geometries: (1) the sandy-gravelly bottomset, (2) the erosional-bypass stage, (3) the fine-grained bottomset and (4) the massive-sandy bottomset. By comparing the typologies of the bottomset, we propose a conceptual model that predicts the occurrence of these four different bottomset stage dynamics depending on the stratigraphic context. During highstand normal regression, the gravelly bottomset develops under subcritical flow. The supercritical flow undergoes a stationary hydraulic jump in the toeset due to the slope break. As a result, a low-relief channel-levees system is formed in the bottomset. The channels are filled/reworked by backstepping conglomeratic lenses interbedded with silty concave-up and concave-down levees. During normal regression, the foreset beds are steeper than during previous stage and scoured in the upper part. In the bottomset, significant erosion recording sediment bypass downstream toward the pro-delta can be observed. During lowstand normal regression, a starved fine silt to shale bottomset onlaps onto the major erosional surface. The bulk of the coarse-grained sediments is stored in the delta topset and foreset. During the transgressive to highstand stage, the former topset and foreset are eroded by high-density turbidity currents and massive-sandy turbidites are deposited in the bottomset, which onlap onto the foreset beds and form a slope apron geometry in the delta toe. The stratigraphic model improves the prediction for the sand distribution within the various parts of the bottomset. This approach is particularly relevant for clastic depositional systems with high sediment discharge and a high accommodation rate. [ABSTRACT FROM AUTHOR]

Facies character, diagenesis, geochemical signature, porosity, permeability, and geometry of the upper Pleistocene Tivoli travertines were investigated integrating information from six borehole cores, drilled along a 3 km N-S transect, and quarry faces, in order to propose a revised depositional model. Travertines overlie lacustrine and alluvial plain marls, siltstones, sandstones and pyroclastic deposits from the Roman volcanic districts. In the northern proximal area, with respect to the inferred hydrothermal vents, travertines accumulated in gently-dipping, decametre-scale shallow pools of low-angle terraced slopes. The intermediate depositional zone, 2 km southward, consisted of smooth and terraced slopes dipping S and E. In the southernmost distal zone, travertine marshes dominated by coated vegetation and Charophytes interfingered with lacustrine siltstones and fluvial sandstones and conglomerates. Travertine carbon and oxygen stable isotope data confirm the geothermal origin of the precipitating spring water. The travertine succession is marked by numerous intraclastic/extraclastic wackestone to rudstone beds indicative of non-deposition and erosion during subaerial exposure, due to temporary interruption of the vent activity or deviation of the thermal water flow. These unconformities identify nine superimposed travertine units characterized by aggradation in the proximal zone and southward progradation in the intermediate to distal zones. The wedge geometry of the travertine system reflects the vertical and lateral superimposition of individual fan-shaped units in response to changes in the vent location, shifting through time to lower elevations southward. The complexity of the travertine architecture results from the intermittent activity of the vents, their locations, the topographic gradient, thermal water flow paths and the rates and modes of carbonate precipitation.

Facies character, diagenesis, geochemical signature, porosity, permeability, and geometry of the upper Pleistocene Tivoli travertines were investigated integrating information from six borehole cores, drilled along a 3 km N-S transect, and quarry faces, in order to propose a revised depositional model. Travertines overlie lacustrine and alluvial plain marls, siltstones, sandstones and pyroclastic deposits from the Roman volcanic districts. In the northern proximal area, with respect to the inferred hydrothermal vents, travertines accumulated in gently-dipping, decametre-scale shallow pools of low-angle terraced slopes. The intermediate depositional zone, 2 km southward, consisted of smooth and terraced slopes dipping S and E. In the southernmost distal zone, travertine marshes dominated by coated vegetation and Charophytes interfingered with lacustrine siltstones and fluvial sandstones and conglomerates. Travertine carbon and oxygen stable isotope data confirm the geothermal origin of the precipitating spring water. The travertine succession is marked by numerous intraclastic/extraclastic wackestone to rudstone beds indicative of non-deposition and erosion during subaerial exposure, due to temporary interruption of the vent activity or deviation of the thermal water flow. These unconformities identify nine superimposed travertine units characterized by aggradation in the proximal zone and southward progradation in the intermediate to distal zones. The wedge geometry of the travertine system reflects the vertical and lateral superimposition of individual fan-shaped units in response to changes in the vent location, shifting through time to lower elevations southward. The complexity of the travertine architecture results from the intermittent activity of the vents, their locations, the topographic gradient, thermal water flow paths and the rates and modes of carbonate precipitation. [ABSTRACT FROM AUTHOR]

Slope sediments on passive and active margins deform and fail across a broad range of scales ranging from loading and sediment remobilization near the sediment–water interface to submarine landslides and mass movements that incorporate significant volumes of slope deposits. Deformational styles are characterized by updip extension and downdip compressional features that occur above a detachment surface. Conditions for failure and deformation include the presence of weak layer(s) that serve as a detachment surface, competency contrasts that allow for detachment and downslope movement, deformation above a detachment surface, and a triggering mechanism(s) that initiates failure. Slope failure processes and products are well documented at scales resolvable by seismic-reflection surveys and in instances of extensive downslope failure, but the processes and products associated with intermediate-scale slope deformation are poorly understood. Intrastratal deformation is defined as stratigraphically isolated zones of deformation bounded above and below by concordant and undeformed strata. In this study, outcrop examples of intrastratal deformation from the Upper Cretaceous Tres Pasos Formation are used to elucidate the influence of depositional architecture on slope deformation. The facies distribution associated with compensational stacking of lobe deposits is shown to have a first-order control on the location and style of deformation. Detachment planes that form in mudstone deposits associated with lobe fringe and interlobe deposits are spatially limited and deformation is restricted to interbedded sandstone and mudstone associated with off-axial lobe positions. Downslope translation was arrested by stratigraphic buttresses associated with more sandstone-prone axial deposits. Emplacement of a regionally extensive mass transport deposit is interpreted as the triggering mechanism for contemporaneous intrastratal deformation of > 60 m of underlying stratigraphy. A vertical increase in ductile deformation through the deformation interval indicates the role of burial depth and compaction. Distinguishing synburial intrastratal deformation (10s of m below seafloor) from tectonic or at-seafloor deformation has important implications for interpretations of burial history, slope stability, and potential triggering mechanisms. [ABSTRACT FROM AUTHOR]

This study investigates the depositional architecture of turbidite lobes from the Southern Laga Basin (Lower Messinian, Central Apennines) and the external controls on its development. Physical stratigraphy and facies analysis on a 1700 m thick interval enabled us unraveling the hierarchical partitioning and internal arrangement of lobes from four units with different degree of topographic confinement. A four-fold hierarchy of depositional bodies was recognized including: i) event beds deposited by single turbidity currents: ii) single lobes, consisting of bed sets with variable degree of sand amalgamation; iii) lobe sets, i.e. depocentre-wide stacks of single lobes and iv) lobe complexes, representing high rank units of greater internal complexity. Field mapping of the studied lobes highlighted a significant change in size and morphology of the receiving depocentre resulting from sediment filling and onlapping of basinal slopes. The lobe depocentre evolved from a funnel-shaped trough with an initial size of ∼150 km 2 to a wider basin reaching a maximum extent of over 500 km 2 , which implies decreasing degree of confinement from older to younger lobes. Comparison of depositional architectures across the studied units points out two end-members: i) confined sheet-like lobes, consisting of topography contained sandbodies with flat geometry and little facies variability in their axial part and ii) semi-confined lobes with a ‘jigsaw’ architecture, comprised of shingled to compensated depositional bodies with lobate to sigmoidal planform and highly variable facies partitioning. The former architecture is interpreted as the product of flow containment of incoming flows by lateral basinal slopes with consequent deposition under confined accommodation space, whereas the latter would record sedimentation within a wider depocentre allowing for free flow expansion and lateral migration of lobes. The different architecture of confined vs. semi-confined lobes has important implications for the hydrocarbon industry as it results in significantly dissimilar structures of permeability and connectivity. [ABSTRACT FROM AUTHOR]

Sedimentary processes of marine turbidite systems under sea-level changes have been the focus of deep-water sedimentology. Compared with well-studied marine basins, the products of deep-water sediment gravity flows responding to lake-level changes in closed lacustrine basins are still poorly understood. In this study, we integrate cores of 10 exploratory wells, logs of 280 development wells, 3D seismic data and geochemical elements from the Eocene Dongying Depression, Bohai Bay Basin, East China to investigate sedimentary mechanisms and depositional architecture of lacustrine turbidite systems under lake-level changes. The studied strata are divided into three parasequence sets (PSS4 ~ PSS2), corresponding to early highstand normal regression with ascending trajectories, late highstand normal regression with flat trajectories, and forced regression with descending trajectories, respectively. From early highstand normal regression to forced regression, the ratios of Fe/Mn and U/Th reveal that the humid climate shifted to the arid climate. More lithofacies clues indicate that turbidites in highstand normal regression were triggered by river floods, whereas counterparts in forced regression were related to sediment failures. There are different architectural features of turbidite systems in three regression stages. PSS4 developed a series of channel belts within which individual channel elements are aggraded vertically. PSS3 is composed of a channelized lobe formed by individual distributary channels migrating laterally. PSS2 is characterized by a suite of compensational stacking debrite tongues. Climate forcing is a crucial factor controlling depositional architecture of the turbidite systems. A relatively humid climate during highstand normal regression led to rising lake-level and frequent floods, which are conducive to the formation of hyperpycnal-fed channel-lobe systems. Nevertheless, during forced regression under an arid climate, the strong progradational clinothems were prone to failure and sediment remobilization, resulting in debrite tongue complexes. This study highlights depositional differences of lacustrine turbidites during regression stages under the control of climate. Meanwhile, it also provides a new predictive model for deep-water hydrocarbon exploration and production in lacustrine basins worldwide. • Lacustrine turbidites in highstand normal regression were induced by river floods. • Lacustrine turbidites in forced regression were triggered by sediment failures. • Lake-level changes control stacking patterns of lacustrine turbidite systems. • Climate forcing controls triggering mechanisms of lacustrine turbidites. [ABSTRACT FROM AUTHOR]

Coastal areas contain interfaces between complex depositional systems as a consequence of the convergence of marine and continental environments. The knowledge of such complex depositional systems is important in understanding of coastal evolution and for coastal management. The present study deals with the subsurface identification of interfaces between fluvial and beach/shallow marine systems, using Ground Penetrating Radar (GPR). GPR profiles were measured along dip direction, at two sites on the coastal plain of Santa Catarina state (Pinheira and Passo de Torres), where deposits of fluvial and beach/foredune ridge systems occur. GPR data showed that fluvial and beach deposits are interdigitated in subsurface, with reflectors showing different downlap directions. The results of this study allow a more complete knowledge of the complex interfaces between marine and continental systems. Also, the identification of hidden older fluvial deposits in the subsurface of coastal plains gives important geotechnical information to be considered in the use and occupation of coastal areas and during prospection for placer deposits. [ABSTRACT FROM AUTHOR]

Process-based and facies models to account for the origin of pre-vegetation (i.e. pre-Silurian) preserved fluvial sedimentary architectures remain poorly defined in terms of their ability to account for the nature of the fluvial conditions required to accumulate and preserve architectural elements in the absence of the stabilizing influence of vegetation. In pre-vegetation fluvial successions, the repeated reworking of bars and minor channels that resulted in the generation and preservation of broad, tabular, stacked sandstone-sheets has been previously regarded as the dominant sedimentary mechanism. This situation is closely analogous to modern-day poorly vegetated systems developed in arid climatic settings. However, this study demonstrates the widespread presence of substantially more complex stratigraphic architectures. The Guarda Velha Formation of Southern Brazil is a >500 m-thick synrift fluvial succession of Cambrian age that records the deposits and sedimentary architecture of three distinct fluvial successions: (i) an early rift-stage system characterized by coarse-grained channel elements indicative of a distributive pattern with flow transverse to the basin axis; and two coeval systems from the early- to climax-rift stages that represent (ii) an axially directed, trunk fluvial system characterized by large-scale amalgamated sandy braid-bar elements, and (iii) a distributive fluvial system characterized by multi-storey, sandy braided-channel elements that flowed transverse to the basin axis. Integration of facies and architectural-element analysis with regional stratigraphic basin analysis, palaeocurrent and pebble-provenance analysis demonstrates the mechanisms responsible for preserving the varied range of fluvial architectures present in this pre-vegetation, rift-basin setting. Identified major controls that influenced pre-vegetation fluvial sedimentary style include: (i) spatial and temporal variation in discharge regime; (ii) the varying sedimentological characteristics of distinct catchment areas; (iii) the role of tectonic basin configuration and its direct role in influencing palaeoflow direction and fluvial style, whereby both the axial and transverse fluvial systems undertook a distinctive response to syn-depositional movement on basin-bounding faults. Detailed architectural analyses of these deposits reveal significant variations in geometry, with characteristics considerably more complex than that of simple, laterally extensive, stacked sandstone-sheets predicted by most existing depositional models for pre-vegetation fluvial systems. These results suggest that the sheet-braided style actually encompasses a varied number of different pre-vegetation fluvial styles. Moreover, this study demonstrates that contemporaneous axial and transverse fluvial systems with distinctive architectural expressions can be preserved in the same overall tectonic and climatic setting. [ABSTRACT FROM AUTHOR]

According to the different geometries and reflected characteristics in the seismic sections, the carbonate platform margin of the northern slope can be summarized as three basic depositional architectures in the Late Ordovician Lianglitage (良里塔格) Formation of the Tazhong (塔中) uplift. The type one mainly located in the west of the carbonate platform margin, and it showed obvious imbricate progradation from the interior to the margin of the platform. The type two was in the middle of the carbonate platform margin, which showed retrogradational stacking pattern in the same transgressive systems tract period, and the slope strata of the platform margin showed progradational sequence in the highstand systems tract period. The type three located in the east of the carbonate platform margin, and it showed the parallel aggradational architecture. The crossing well section along the northern slope of the Tazhong carbonate platform showed that the depositional thickness became thinner from the east to the west. The thickest belt located in the east of the platform margin, and became thinner rapidly towards the basin and the platform interior. These indicated that the paleogeomorphology of the Tazhong uplift was probably high in the west and low in the east during the period of the Late Ordovician Lianglitage Formation. According to the interpretation of seismic profiles and the computer modelling result, the depositional architectures of sequence O l-2 showed aggradation, retrogradation and progradation from the east to the west of the carbonate platform margin during the transgression period. This meant that the accommodation became smaller gradually from the east to the west along the northern carbonate platform margin of the Tazhong uplift. The difference of the accommodation was probably caused by the difference of tectonic subsidence. Also, computer-aided modelling can be used to deeply understand the importance of various control parameters on the carbonate platform depositional architectures and processes. [ABSTRACT FROM AUTHOR]

Abstract: Multibeam bathymetry, high (sleeve airguns) and very high resolution (parametric system-TOPAS-) seismic records were used to define the morphosedimentary features and investigate the depositional architecture of the Cantabrian continental margin. The outer shelf (down to 180–245 m water depth) displays an intensively eroded seafloor surface that truncates consolidated ancient folded and fractured deposits. Recent deposits are only locally present as lowstand shelf-margin deposits and a transparent drape with bedforms. The continental slope is affected by sedimentary processes that have combined to create the morphosedimentary features seen today. The upper (down to 2000 m water depth) and lower (down to 3700–4600 m water depth) slopes are mostly subject to different types of slope failures, such as slides, mass-transport deposits (a mix of slumping and mass-flows), and turbidity currents. The upper slope is also subject to the action of bottom currents (the Mediterranean Water — MW) that interact with the Le Danois Bank favouring the reworking of the sediment and the sculpting of a contourite system. The continental rise is a bypass region of debris flows and turbidity currents where a complex channel-lobe transition zone (CLTZ) of the Cap Ferret Fan develops. The recent architecture depositional model is complex and results from the remaining structural template and the great variability of interconnected sedimentary systems and processes. This margin can be considered as starved due to the great sediment evacuation over a relatively steep entire depositional profile. Sediment is eroded mostly from the Cantabrian and also the Pyrenees mountains (source) and transported by small stream/river mountains to the sea. It bypasses the continental shelf and when sediment arrives at the slope it is transported through a major submarine drainage system (large submarine valleys and mass-movement processes) down to the continental rise and adjacent Biscay Abyssal Plain (sink). Factors controlling this architecture are tectonism and sediment source/dispersal, which are closely interrelated, whereas sea-level changes and oceanography have played a minor role (on a long-term scale). [Copyright &y& Elsevier]

Abstract: The Dezadeash Formation is a northwest trending belt of predominantly Jura–Cretaceous deep-marine siliciclastic rocks in southwestern Yukon, Canada. It is truncated to the southwest by the Denali Fault System, a major transcurrent fault along which ∼370 km of dextral slip occurred in post-Early Cretaceous time, and it is flanked to the northeast by the Kluane Schist, a mainly mica–quartz schist assemblage of unknown age and origin. This study provides a robust quantitative description of lithofacies comprising a point-source mud/sand-rich turbidite system: approximately 16 335 m of measured strata from 75 sections throughout the Dezadeash Formation indicate that up to 29 lithofacies types are present and these are dominated by thin- to thick-bedded sandstone–mudstone couplets and medium- to thick-bedded sandstone. The various lithofacies are grouped into conglomerate, sandstone, sandstone–mudstone, and siltstone–mudstone lithofacies associations, which are interpreted as slide, channel-lobe transition, lobe, and overbank architectural elements, respectively. Stacked channel-lobe transition and lobe elements predominate, but the depositional architecture displays no apparent, overall vertical trend. The Dezadeash Formation represents mainly the lower middle and lower subdivisions of a point-source, mud/sand-rich turbidite system that records a single stage of fan growth as it prograded transversely from a volcano-plutonic arc into the basin. [Copyright &y& Elsevier]

Abstract: The innermost shelf of the eastern Korea Strait is a ria-type coastal sea comprising islands, intervening passageways and embayments. A detailed analysis of high-resolution (1−10 kHz) subbottom profiles and core sediments from this area reveals complicated depositional and distributional patterns of the Holocene mud deposits related to complex topography with varying supply of the adjacent Nakdong riverine sediments. Sediments from the Nakdong River were bifurcated around Gadeok Island, forming two proximal systems: Nakdong and western Gadeok systems. These proximal systems prograded offshore (southward) by active sediment supply from the Nakdong River in the early stage. Suspended sediments passing through the Nakdong system formed the distal (Gadeok Waterway and eastern Geoje) systems in the area between the northern Geoje and Gadeok islands. These distal systems show a northwestward (onshore) prograding tendency to Jinhae Bay, the biggest bay in the vicinity of the Nakdong estuary in which the Jinhae Bay system developed. In the late stage, a remarkable decrease of sediment supply from the Nakdong River has caused retrograding geometry of the two proximal systems. However, the most distal (Jinhae Bay) system has continuously prograded bayward due to the persistent supply of sediments resuspended by strong tidal currents from nearby distal (Gadeok Waterway and eastern Geoje) systems. These complex depositional features indicate that topography has an important influence on depositional developments of the Holocene mud deposits by controlling path and intensity of sediment dispersal and resuspension processes. [Copyright &y& Elsevier]

Seismic-scale continuous exposures of an Upper Carboniferous (Bashkirian–Moscovian) carbonate platform (N Spain) provide detailed information about the lithofacies and stratal geometries (quantified with differential global positioning system measurements) of microbial boundstone-dominated, steep prograding and aggrading platform margins. Progradational and aggradational platform-to-slope transects are characterized by distinct lithological features and stratal patterns that can be applied to the understanding of geometrically comparable, high-relief depositional systems. The Bashkirian is characterized by rapid progradation at rates of 415–970 m My−1. Characteristic outer-platform facies are high-energy grainstones with coated intraclasts, ooids and pisoids, moderate-energy algal-skeletal grainstones to packstones and lower energy algal packstone and boundstone units. The Moscovian aggradational phase is characterized by aggradation rates of 108 m My−1. Coated-grain shoals are less common, whereas crinoidal bars nucleated in well-circulated settings below wave-base. Boundstones form a belt (30–300 m wide) at the platform break and interfinger inwards with massive algal-skeletal wackestones (mud-rich banks). The progradational phase has divergent outer-platform strata with basinward dips of 12° to 2°. Steep clinoforms with dips of 20–28° are 650–750 m in relief and possibly sigmoidal to concave in the lower part. The basinward-dipping outer-platform strata might be depositional for less than 6°, consistent with lithofacies deepening seaward. The basinward dip is attributed to the downward shift of upper-slope boundstone, forced by late highstand and relative sea-level fall, and to compaction-induced differential subsidence during progradation. The aggradational phase is characterized by horizontally layered platform strata. Clinoforms steepen to 30–45° reaching heights of 850 m and are planar to concave. The evolution from progradation to aggradation, at the Bashkirian–Moscovian boundary, is attributed to increased foreland-basin subsidence and decreased boundstone accumulation rates. Progradation was primarily controlled by boundstone growth rather than by highstand shedding from the platform top. Within the major phases, aggradational–progradational increments are produced by third- to fourth-order relative sea-level fluctuations. [ABSTRACT FROM AUTHOR]

The Tertiary Kuqa depression is a foreland basin generated by flexural subsidence resulting from the southward thrusting of the southern Tianshan Mountains. Tertiary basin fills of the depression can be classified into four tectonic sequences bounded by gentle angular unconformities. The sequences are composed of two parts, the lower transgressive and the upper progradational successions, which are separated by a regional maximum transgressive surface. The development of these sequences is attributed to the foreland tectonic process from flexural subsidence caused by thrust loading to rebounded uplift due to the erosion and stress release. The generation of the angular unconformities defining the tectonic sequences has been interpreted as the result of the rebounded uplift and the following thrusting. It has been found that there is a significant difference in depositional pattern between the northeastern and the northwestern margins. The relatively strong thrusting and mountain building occurring along the northwestern margin resulted in the development of thick-bedded alluvial fan and angular unconformities. The northeastern margin, in contract, lacks thick alluvial fan accumulation due to weak thrusting. This difference is likely related to the pre-existing east-west partition of the basin basement. [ABSTRACT FROM AUTHOR]

Late Oligocene to Early Miocene deltaic systems (the Zhuhai Formation) comprise the most important oil and gas reservoirs in the Pearl River Mouth Basin in the northern South China Sea and their changes in depositional architecture reflect the interplay of basin kinetic energy, sea level change and sediment supply. Based on the analysis of well log, seismic and core data, depositional styles of deltaic systems, sequence stratigraphy and their controlling factors are systematically documented. Three kinds of deltaic systems (braided river, meandering river and incised river deltas) are distinguished from the inner shelf, middle–outer shelf to shelf edge within a dynamic sequence framework. The braided river and braided river deltaic deposits along the inner shelf are mainly composed of vertically-stacked, thick-bedded channel sandstones and broad-lobate shaped delta front sandy deposits. The meandering river deltaic systems distributed in the middle–outer shelf are characterized by relatively thick delta front sandstones, interdistributary bay fills and prodelta mudstones with turbidite sheets in places. Incised river deltaic systems were generally developed at the shelf margin, with clinoform thickness ranging from 200 to 1200 m, and were commonly associated with large-scale slump and slope fan deposits. The temporal–spatial distribution of deltaic systems within the sequence framework shows a distinct pattern: the braided river delta system mainly developed in the early stage of highstand systems tracts; meandering river delta systems occurred in the middle–late stage of highstand systems tracts; and incised river delta systems generally formed in the falling stage systems tract. Depositional architectures of deltaic systems reveal that the basin kinetic condition varied from the inner shelf to shelf edge. Inner shelf braided river deltaic systems were dominated by fluvial processes, whereas middle–outer shelf meandering river delta and shelf edge incised river delta systems were reworked by waves and alongshore currents. The migration of deltaic systems across the entire wide shelf within the transgression–regression cycle is regarded as the result of high-amplitude sea level fluctuations under coolhouse or icehouse climatic condition. High progradation rates of shelf edge deltaic systems reflect enormous sediment supply resulting from the continuous uplift of the drainage area during the early post-rift period and the intense erosion triggered by glacial climate. • Delta types from the inner shelf to shelf edge within the sequence framework • Depositional architecture of different delta systems and favorable reservoirs • Constraints of sea level change, sediment supply and basin kinetic energy [ABSTRACT FROM AUTHOR]

Channels are considered effective conduits that deliver terrigenous sediments into related depositional basins, and they are the targets of petroleum exploration and production. Three-dimensional (3D) seismic data, well data, and attribute maps were used to study five types of channels observed in the Shahejie Formation of the Zhanhua Depression, namely erosional channels, confined channels, semi-confined channels, distributary channels, and transitional channels. The channels originated from hyperpycnal flows related to bed load, suspended load, and lofting processes from proximal to distal regions, which were primarily accumulated on medium and low terrains. The hyperpycnal channel systems were primarily identified as three stages with morphological changes in the Es3l and Es3m intervals on a seismic section. Stage 1 was developed during the late period of the Es3l interval, and stages 2 and 3 were developed during the early and middle periods, respectively, of the Es3m interval. Stage 1 is the initial/young stage formed during a phase of low accommodation. Channels of stage 1 are predominantly entrenched with moderately aggregated width and thick channelized splays. Stage 2 is the transitional stage formed during a phase of increasing accommodation. Channels of stage 2 are predominantly meandering with narrowly aggregated width and dispersed frontal splays. Stage 3 is a waned stage, formed during the events of increasing lake levels without comparable increase in sediment flux. This stage involves slight incisions, broad U-shaped morphology channels, and the prevalence of overbank sediments. The depositional architectures, processes, and the development of hyperpycnal channel systems correspond with the lake level and climate conditions of the proposed stages and were controlled by tectonic activity and source supply. Understanding the distribution and development of lacustrine hyperpycnal channels is important to improve and enrich theories of lacustrine sediment gravity flow. • Five types of channels were identified in the Shahejie Formation of the Zhanhua Depression. • Hyperpycnal channel systems, consisted by five types of channels, were categorized as three stages. • Tectonic activity, sediment supply, climate conditions, and lake level were demonstrated as the factors controlling the evolution of the lacustrine hyperpycnal channel system. [ABSTRACT FROM AUTHOR]

Submarine canyon system in the Miocene Pearl River Mouth Basin, northern continental margin of the South China Sea, records the process of sediments transported from shelf margin to advanced abyssal plain and comprises important petroleum reservoirs in the basin. Based on integrated analysis of seismic, well logs and core data, the sequence framework, depositional architecture and controlling factors of the submarine canyon system are well documented. As a composite sequence bounded by regional unconformity, the Zhujiang Formation (CS1) can be divided into 5 sequences (CS1-1-CS1-5), and the lower CS1-2 and CS1-3 are the main strata that the submarine canyon system developed. The submarine canyon system can be divided into five segments (A-E) by their distinct geomorphology and depositional architectures. From Segment A to E, the channels in the submarine canyon system transform from "V" shaped single channel, "U" shaped single channel, "gull-wing" shaped channel-levee complex, "W" shaped branch channels to mound shaped distal composite channel and front splay deposits. This is accordantly consistent with sedimentary process of the channels transitional from erosional, erosional-aggradational, aggradational and then lateral migrational. The changing interaction of multi-source sediment supply, differential tectonic subsidence and relative sea level change are considered to be the major control on the development and evolution of the submarine canyon system. The differential tectonic subsidence since the Late Oligocene produced the adequate slope angle, sufficient accommodation and distinct basin geomorphology for the development and segmentation of the submarine canyon system. Slope-gully to slope fan deposits fed by the shelf margin delta systems from the Paleo-Pearl River and the northeastern Dongsha Uplift converged into the submarine canyon system, providing abundant sediments for its development. Relative sea level changes, especially the two regional regressions with abundant sediment supply have made great influence on the evolution of the submarine canyon system. • A giant submarine canyon system consisting of two periods of incised channels is recognized in the Lower-Middle Miocene. • The canyon system is made up of five segments with different geomorphology and depositional architecture. • The canyon system was constrained by tectonic subsidence, multi-source sediment supply and relative sea level change. [ABSTRACT FROM AUTHOR]

The tectonic histories of continental rift basins tend to be complex, with several episodes of subsidence, extensional and strike-slip tectonic activity and diverse paleogeographic characteristics. Intrabasinal and extrabasinal source areas influence deposition resulting in several sedimentary episodes and depositional architectures. In this study, we use 3D seismic data covering Liaodong Bay and well-logging data to analyze sediment source area, paleo-valleys, and slopes to determine the characteristics, distribution and relationships between the source, transport, and sedimentary systems in the Liaodong Bay Sub-basin, which is an Oligocene strike-slip extensional basin with two regional extrabasinal source areas and a local intrabasinal source area in the basin fill succession. Four types of basin-marginal fluvial paleo-valleys are identified in the Liaodong Bay Sub-basin including incised V-, bifurcate V-, wide V- and shallow V- types. The energy of current decreased successively from incised V-, to bifurcate V-, to wide V-type valleys, which ultimately evolved to become shallow V- type during the late stages of a rift lake basin. These sedimentary systems are grouped into five extrabasinal and two intrabasinal types with diverse depositional architectures, based on their slope shapes. The sedimentation processes of the Liaodong Bay Sub-basin were influenced by the tectonic activity, paleogeomorphology and climate condition during the different stages of the strike-slip extensional basin and controlled the accumulation of sandy sediments. • 3D seismic data and well-logs were analyzed. • Depositional architectures of five extrabasinal and two intrabasinal sedimentary systems have been identified. • Sedimentation processes and main controlling factors during the Oligocene in the Liaodong Bay Sub-basin have been studied. [ABSTRACT FROM AUTHOR]

The stratigraphic record of distributive fluvial systems is commonly characterised by frequent and complex interstratification of palaeosols among channel and overbank deposits. However, current models focus primarily on sedimentation and pay only limited attention to palaeopedogenesis, thereby failing to incorporate important palaeoenvironmental and stratigraphic information. This study proposes a pedosedimentary model for distributive fluvial systems that depicts and accounts for two palaeopedogenetic trends: one downdip, in relation to distality from the fan apex, and one along-strike, in relation to distance from active channel belts. Palaeosols are reported in detail from an Upper Cretaceous succession of the Bauru Basin, southeastern Brazil, through the application of macro-, micromorphological and geochemical studies, combined with facies and architectural-element analyses of sediments. In the downdip palaeopedogenetic trend, the proximal zone of the depositional system is characterised by a dominance of well-drained Inceptisols that develop on amalgamated channel fills; in the medial zone, Inceptisols occur interlayered with overbank deposits containing Entisols and poorly drained Vertisols. The distal zone preserves more mature and poorly drained Inceptisols developed on deposits of overbank and sporadic distal channel fills. These pedotypes show an increase in maturity and hydromorphism, moving away from the apex to the fan toe. This is likely linked to (i) the progressive approach of the topographic surface to the water table, and (ii) the average increase in distance to an active channel belt in distal locations. The along-strike palaeopedogenetic trend culminates in poorly developed palaeosols in floodplain regions that correspond to topographic depressions located between channel belts and which were subject to recurrent floods. Because palaeopedogenesis in the floodplain region is penecontemporaneous to sedimentation, pedotypes show an increase in maturity, bioinduced calcification and hydromorphism with distance from the active channels; they pass laterally from Entisols and Inceptisols near active channels, to Vertisols away from active channels. Conversely, following avulsion, abandoned channel belts remain as topographically elevated alluvial ridges located at some distance from the newly active channels and positioned above the water table and this leads to the development of better drained and better developed Inceptisols relative to pedotypes of the floodplain region. Overall, both palaeopedogenetic trends demonstrate the overriding controls of topography, sedimentation rate and parent material on pedogenesis, with only minor climatic influence. This work offers a novel pedosedimentary model for distributive fluvial systems and highlights the palaeoenvironmental significance of palaeosol trends, providing new constraints for the recognition of distributive fluvial systems in the rock record. Unlabelled Image [ABSTRACT FROM AUTHOR]