Sediment dispersal and redistributive processes in axial and transverse deep‐time source‐to‐sink systems of marine rift basins: Dampier Sub‐basin,Northwest Shelf,Australia

Morphological scaling relationships between source‐to‐sink segments have been widely explored in modern settings, however, deep‐time systems remain difficult to assess due to limited preservation of drainage basins and difficulty in quantifying complex processes that impact sediment dispersals. Integration of core, well‐logs and 3‐D seismic data across the Dampier Sub‐basin, Northwest Shelf of Australia, enables a complete deep‐time source‐to‐sink study from the footwall (Rankin Platform) catchment to the hanging wall (Kendrew Trough) depositional systems in a Jurassic late syn‐rift succession. Hydrological analysis identifies 24 drainage basins on the J50.0 (Tithonian) erosional surface, which are delimited into six drainage domains confined by NNE‐SSW trending grabens and their horsts, with drainage domain areas ranging between 29 and 156 km². Drainage outlets of these drainage domains are well preserved along the Rankin Fault System scarp, with cross‐sectional areas ranging from 0.08 to 0.31 km². Corresponding to the six drainage domains, sedimentological and geomorphological analysis identifies six transverse submarine fan complexes developing in the Kendrew Trough, ranging in areas from 43 to 193 km². Seismic geomorphological analysis reveals over 90‐km‐long, slightly sinuous axial turbidity channels, developing in the lower topography of the Kendrew Trough which erodes toe parts of transverse submarine fan complexes. Positive scaling relationships exist between drainage outlet spacing and drainage basin length, and drainage outlet cross‐sectional area and drainage basin area, which indicates the geometry of drainage outlets can provide important constraints on source area dimensions in deep‐time source‐to‐sink studies. The broadly negative bias of fan area to drainage basin area ratios indicates net sediment losses in submarine fan complexes caused by axial turbidity current erosion. Source‐to‐sink sediment balance studies must be done with full evaluating of adjacent source‐to‐sink systems to delineate fans and their associated up‐dip drainages, to achieve an accurate tectonic and sedimentologic picture of deep‐time basins.     

Source‐to‐sink analysis in an active extensional setting: Holocene erosion and deposition in the Sperchios rift,central Greece

We present a source‐to‐sink analysis to explain sediment supply variations and depositional patterns over the Holocene within an active rift setting. We integrate a range of modelling approaches and data types with field observations from the Sperchios rift basin, Central Greece that allow us to analyse and quantify (1) the size and characteristics of sediment source areas, (2) the dynamics of the sediment routing system from upstream fluvial processes to downstream deposition at the coastline, and (3) the depositional architecture and volumes of the Holocene basin fill. We demonstrate that the Sperchios rift comprises a ‘closed’ system over the Holocene and that erosional and depositional volumes are thus balanced. Furthermore, we evaluate key controls in the development of this source‐to‐sink system, including the role of pre‐existing topography, bedrock erodibility and lateral variations in the rate of tectonic uplift/subsidence. We show that tectonic subsidence alone can explain the observed grain size fining along the rift axis resulting in the downstream transition from a braided channel to an extensive meander belt (>15 km long) that feeds the fine‐grained Sperchios delta. Additionally, we quantify the ratios of sediment storage to bypass for the two main footwall‐sourced alluvial fan systems and relate the fan characteristics to the pattern and rates of fault slip. Finally, we show that ≥40% of the sediment that builds the Sperchios delta is supplied by ≤22% of the entire source area and that this can be primarily attributed to a longer‐term (~10⁶ years) transient landscape response to fault segment linkage. Our multidisciplinary approach allows us to quantify the relative importance of multiple factors that control a complex source‐to‐sink system and thus improve our understanding of landscape evolution and stratigraphic development in active extensional tectonic settings.     

Source‐to‐sink analysis of ancient sedimentary systems using a subsurface case study from the Møre‐Trøndelag area of southern Norway: Part 2 – sediment dispersal and forcing mechanisms

The composition, volume and stratigraphic organisation of submarine fan systems deposited along continental margins are expected to reflect the landscape from which the sediment was derived. During the Late Cretaceous, the Møre‐Trøndelag margin, Norwegian North Sea was dominated by the deposition of deep‐marine fines; the emplacement of 11 sand‐rich submarine fan systems occurred only during a c. 3 Myr period in the Turonian‐Coniacian. The systems were fed by sediment that was routed through submarine canyons incised into the basin margin; the canyons are underlain by angular unconformities and are interpreted to have resulted from tectonically induced changes in slope physiography and erosion by gravity flows. The areal extent of the onshore drainage catchments that supplied sediment to the fans has been estimated based on scaling relationships derived from modern source‐to‐sink systems. The results of our study suggest that the Turonian fans were sourced by drainage catchments that were up to ca.3600 km², extending more than ca.100 km inland from the palaeo‐shoreline. The estimated inboard catchment extent correlates with the innermost structures of a large, long‐lived, basement‐involved, normal fault complex. On the basis of our analysis, we conclude that increased sediment supply to the Turonian fan systems reflects tectonic rejuvenation of the landscape, rather than eustatic sea‐level or climate fluctuations. The duration of fan deposition is thus interpreted to reflect the ‘relaxation time’ of the landscape following tectonic perturbation, and fan system retrogradation and abandonment is interpreted to reflect the eventual depletion of the onshore sediment source. We demonstrate that a better understanding of the stratigraphic variability in deepwater depositional systems can be gained by taking a complete source‐to‐sink view of ancient sediment dispersal systems.     

Lateral variability in clinoform trajectory,process regime,and sediment dispersal patterns beyond the shelf‐edge rollover in exhumed basin margin‐scale clinothems

Sediment supply rate and accommodation regime represent primary controls on the depositional architecture of basin margin successions, but their interaction is commonly inferred from 2D dip profiles and/or with limited constraints on sedimentary facies. In this study, three parallel (>40 km long) 2D depositional oblique‐dip profiles from outcrops of the lower Waterford Formation (Karoo Basin, South Africa) have been correlated. This data set provides a rare opportunity to assess the lateral variability in the sedimentary process record of the shelf‐to‐slope transition for eight successive clinothems over a 900 km² area. The three profiles show similar shelf‐edge rollover trajectories, but this belies significant along‐margin variability in sedimentary processes and down‐dip sediment supply. The depositional architecture of three successive clinothems (WfC 3, 4 and 5) also show along‐shelf physiographic differences. The reconstructed shelf‐edge rollover position is not straight, and a westward curve to the north coincides with an area of greater sand supply to the slope beyond a shelf dominated by wave and storm processes. All the clinothems thicken northwards, indicating an along‐margin long‐term increase in accommodation that was maintained through multiple shoreline transits across the shelf. The origin of the differential subsidence cannot be discriminated confidently between tectonic or compaction processes. The interplay of basin margin physiography, differential subsidence rate and process regime resulted in significant across‐strike variability in the style and timing of sediment dispersal patterns beyond the shelf‐edge rollover. This study highlights the challenge for accurate prediction of the sediment partitioning across the shelf‐edge rollover in subsurface studies.     

Forward stratigraphic modelling of sediment pathways and depocentres in salt‐influenced passive‐margin basins: Lower Cretaceous,central Scotian Basin

Source‐to‐sink studies and numerical modelling software are increasingly used to better understand sedimentary basins, and to predict sediment distributions. However, predictive modelling remains problematic in basins dominated by salt tectonics. The Lower Cretaceous delta system of the Scotian Basin is well suited for source‐to‐sink studies and provides an opportunity to apply this approach to a region experiencing active salt tectonism. This study uses forward stratigraphic modelling software and statistical analysis software to produce predictive stratigraphic models of the central Scotian Basin, test their sensitivity to different input parameters, assess proposed provenance pathways, and determine the distribution of sand and factors that control sedimentation in the basin. Models have been calibrated against reference wells and seismic surfaces, and implement a multidisciplinary approach to define simulation parameters. Simulation results show that previously proposed provenance pathways for the Early Cretaceous can be used to generate predictive stratigraphic models, which simulate the overall sediment distribution for the central Scotian Basin. Modelling confirms that the shaly nature of the Naskapi Member is the result of tectonic diversion of the Sable and Banquereau rivers and suggests additional episodic diversion during the deposition of the Cree Member. Sand is dominantly trapped on the shelf in all units, with transport into the basin along salt corridors and as a result of turbidity current flows occurring in the Upper Missisauga Formation and Cree Member. This led to sand accumulation in minibasins with a large deposit seawards of the Tantallon M‐41 well. Sand also appears to bypass the basin via salt corridors which lead to the down‐slope edge of the study area. Sensitivity analysis suggests that the grain size of source sediments to the system is the controlling factor of sand distribution. The methodology applied to this basin has applications to other regions complicated by salt tectonics, and where sediment distribution and transport from source‐to‐sink remain unclear.     

Clinoform growth in a Miocene,Para‐tethyan deep lake basin: thin topsets,irregular foresets and thick bottomsets

Late Miocene lacustrine clinoforms of up to 400 m high are mapped using a 1700 km² 3‐D seismic data set in the Dacian foreland basin, Romania. Eight Meotian clinoforms, constructed by sediment from the South Carpathians, prograded around 25 km towards southwest. The individual clinothems show thin (10–60 m thick), if any, topsets, disrupted foresets and highly aggradational bottomsets. Basin‐margin accretion occurred in three stages with changing of clinoform heights and foreset gradients. The deltaic system prograded into an early‐stage deep depocenter and contributed to high gradient clinoforms whose foresets were dominated by closely (100–200 m) spaced 1.5–2 km wide V‐shaped sub‐lacustrine canyons. During intermediate‐stage growth, 2–4 km wide canyons were dominant on the clinoform foresets. From the early to intermediate stages, the lacustrine shelf edges were consistently indented. The late‐stage outbuilding was characterised by smaller clinoforms with smoother foresets and less indentation along the shelf edge. Truncated and thin topsets persisted through all three stages of clinoform evolution. Nevertheless, the resulting long‐term flat trajectory shows alternating segments of forced and low‐amplitude normal regressions. The relatively flat trajectory implies a constant base level over time and was due to the presence of the Dacian–Black Sea barrier that limited water level rise by spilling to the Black Sea. Besides the characteristic shelf‐edge incision of the thin clinoform topsets and the resultant sediment bypass at the shelf edge, the prolonged regressions of the shelf margin promoted steady sediment supply to the basin. The high sediment supply at the shelf edges generated long‐lived slope sediment conduits that provided sustained sediment transport to the basin floor. Clinothem isochore maps show that large volumes of sediment were partitioned into the clinoform foresets, and especially the bottomsets. Sediment predominantly derived from frequent hyperpycnal flows contributed to very thick, ca. 300–400 m in total, bottomsets. Decreasing subsidence over time from the foredeep resulted in diminishing accommodation and clinoform height, reduced slope channelization and smoother slope morphology.     

Sink‐to‐source: Influence of offshore dynamics on upstream processes

When we model fluvial sedimentation and the resultant alluvial stratigraphy, we typically focus on the effects of local parameters (e.g., sediment flux, water discharge, grain size) and the effects of regional changes in boundary conditions applied in the source region (i.e., climate, tectonics) and at the shoreline (i.e., sea level). In recent years this viewpoint has been codified into the “source‐to‐sink” paradigm, wherein major shifts in sediment flux, grain‐size fining trends, channel‐stacking patterns, floodplain deposition and larger stratigraphic systems tracts are interpreted in terms of (1) tectonic and climatic signals originating in the hinterland that propagate downstream; and (2) eustatic fluctuation, which affects the position of the shoreline and dictates the generation of accommodation. Within this paradigm, eustasy represents the sole means by which downstream processes may affect terrestrial depositional systems. Here, we detail three experimental cases in which coastal rivers are strongly influenced by offshore and slope transport systems via the clinoform geometries typical of prograding sedimentary bodies. These examples illustrate an underdeveloped, but potentially important “sink‐to‐source” influence on the evolution of fluvial‐deltaic systems. The experiments illustrate the effects of (1) submarine hyperpycnal flows, (2) submarine delta front failure events, and (3) deformable substrates within prodelta and offshore settings. These submarine processes generate (1) erosional knickpoints in coastal rivers, (2) increased river channel occupancy times, (3) rapid rates of shoreline movement, and (4) localized zones of significant offshore sediment accumulation. Ramifications for coastal plain and deltaic stratigraphic patterns include changes in the hierarchy of scour surfaces, fluvial sand‐body geometries, reconstruction of sea‐level variability and large‐scale stratal geometries, all of which are linked to the identification and interpretation of sequences and systems tracts.     

Sediment fluxes and buffering in the post‐glacial Indus Basin

The Indus drainage has experienced major variations in climate since the Last Glacial Maximum (LGM) that have affected the volumes and compositions of the sediment reaching the ocean since that time. We here present a comprehensive first‐order source‐to‐sink budget spanning the time since the LGM. We show that buffering of sediment in the floodplain accounts for ca. 20–25% of the mass flux. Sedimentation rates have varied greatly and must have been on average three times the recent, predamming rates. Much of the sediment was released by incision of fluvial terraces constructed behind landslide dams within the mountains, and especially along the major river valleys. New bedrock erosion is estimated to supply around 45% of the sedimentation. Around 50% of deposited sediment lies under the southern floodplains, with 50% offshore in large shelf clinoforms. Provenance indicators show a change of erosional focus during the Early Holocene, but no change in the Mid–Late Holocene because of further reworking from the floodplains. While suspended loads travel rapidly from source‐to‐sink, zircon grains in the bedload show travel times of 7–14 kyr. The largest lag times are anticipated in the Indus submarine fan where sedimentation lags erosion by at least 10 kyr.     

Sediment partitioning,continental slopes and base‐of‐slope systems

Deciphering the role slope topography plays in partitioning sediment on siliciclastic continental slope and base‐of‐slope systems helps our understanding of slope depositional processes in significant ways: (1) by validation of large‐scale depositional process models for continental margins, (2) by validation of numerical basin‐scale stratigraphic forward models used to test and deploy source‐to‐sink (S2S) concepts and (3) by creating models for setting reservoir presence and quality expectations in frontier areas poorly constrained by wells and seismic. A global database consisting of >700 km of drilled stratigraphy provide empirical rock data lacking from most S2S studies. Analysis of calibrated seismic stratigraphic units characterised using the contextual framework laid out in this paper show that both gross depositional environments (GDEs) and sand content occur across slope profiles in systematic ways. The challenge in using these observations to quantify reservoir risk and uncertainty lies with relating the observations to depositional processes that can be used to characterise frontier basins that lack calibration. Depositional process‐based understanding encoded in 3D stratigraphic forward models (SFM) can simulate both lithologies and GDEs providing broad predictions for exploration at the scale of an entire basin or slope system. Stratigraphic forward models allow the integration of S2S understanding and provide a framework for testing sediment‐partitioning hypotheses in frontier settings. Valid S2S models must balance sediment yield from the source catchments with sinks, and be consistent with basin specific observations. The proportions of GDEs across the slope provide additional validation criteria to ensure the models are plausible.     

Shelf-margin clinoforms and prediction of deepwater sands

Early Eocene successions from Spitsbergen and offshore Ireland, showing well‐developed shelf‐margin clinoforms and a variety of deepwater sands, are used to develop models to predict the presence or absence of turbidite sands in clinoform strata without significant slope disturbance/ponding by salt or mud diapers. The studied clinoforms formed in front of narrow to moderate width (10–60 km) shelves and have slopes, 2–4°, that are typical of accreting shelf margins. The clinoforms are evaluated in terms of both shelf‐transiting sediment‐delivery systems and the resultant partitioning of the sand and mud budget along their different segments. Although this sediment‐budget partitioning is controlled by sediment type and flux, shelf width and gradient, process regime on the shelf and relative sea‐level behaviour, the most tell‐tale or predictive signs in the stratigraphic record appear to be (1) sediment‐delivery system type, (2) degree of shelf‐edge channelling and (3) character of shelf‐edge trajectory through time. The clinoform data sets from the Porcupine Basin (wells and 3‐D seismic) and from the Central Basin on Spitsbergen (outcrops) suggest that river‐dominated deltas are the most efficient delivery systems for dispersing sand into deep water beyond the shelf‐slope break. In addition, low‐angle or flat, channelled shelf‐edge trajectories associate with co‐eval deepwater slope and basin‐floor sands, whereas rising trajectories tend to associate with muddy slopes and basin floors. Characteristic features of the shelf‐edge, slope and basin‐floor segments of clinoforms for these trajectory types are documented. Seismic lines along the slope to basin‐floor transects tend to show apparent up‐dip sandstone pinchouts, but most of these are likely to be simply sidelap features. Dip lines aligned along the axes of sandy fairways show that stratigraphic traps are unlikely, unless slope channels become mud‐filled or are structurally partitioned. Another feature that is prominent in the data sets examined is the lack of slope onlap. During the relative rise of sea level back up to the shelf, the clinoform slopes are generally mud‐prone and they are characteristically aggradational.     

Salt tectonic controls on deep‐water turbidite depositional systems: Miocene,southwestern Lower Congo Basin,offshore Angola

Regionally extensive 3D seismic data from the Lower Congo Basin, offshore Angola, have been used to investigate the influence of salt‐related structures on the location, geometry and evolution of Miocene deep‐water depositional systems. Isochron variations and cross‐sectional lap‐out relationships have then been used to qualitatively reconstruct the syn‐depositional morphology of salt‐cored structures. Coherence and Red‐green‐blue‐blended spectral decomposition volumes, tied to cross‐sectional seismic facies, allow imaging of the main sediment transport pathways and the distribution of their component seismic facies. Major sediment transport pathways developed in an area of complex salt‐related structures comprising normal faults, isolated diapirs and elongate salt walls with intervening intraslope basins. Key structural controls on the location of the main sediment transport pathways and the local interaction between lobe‐channel‐levee systems and individual structures were the length and height of structures, the location and geometry of segment boundaries, the growth and linkage of individual structures, and the incidence angle between structural strike and flow direction. Where the regional flow direction was at a high angle to structural strike, transport pathways passed progressively through multiple intraslope basins in a fill and spill manner. Segment boundaries and structural lows between diapirs acted as spill points, focusing sediment transport between intraslope basins. Channel–lobe transitions are commonly associated with these spill points, where flows expanded and entered depocentres. Deflection of channel‐levee complexes around individual structures was mainly controlled by the length of structures and incidence angle. Where regional flow direction was at a low angle to structural strike, sediment transport pathways ran parallel to structure and were confined to individual intraslope basins for many tens of kilometres. Spill between intraslope basins was rare. The relative position of structures and their segment boundaries was fixed during the Miocene, which effectively pinned the locations where sediment spilled from one intraslope basin to the next. As a result, major sediment transport pathways were used repeatedly, giving rise to vertically stacked lobe‐channel‐levee complexes along the pathways. Shadow zones devoid of coarse clastics developed in areas that were either structurally isolated from the sediment transport pathways or bypassed as a result of channel diversion.     

Morphology and sedimentary systems in the Central Bransfield Basin, Antarctic Peninsula: sedimentary dynamics from shelf to basin

A detailed regional characterization of the physiography, morphology and sedimentary systems of the Central Bransfield Basin (CBB) was carried out using swath bathymetry and high‐ and very high‐resolution seismic profiles. The basin margins show continental shelves with numerous glacial troughs, and continental slopes where relatively wide and flat slope platforms represent the middle domain in an atypical physiographic scenario in glaciated margins. Although the CBB is tectonically active, most of the morphologic features are sedimentary in origin, and can be classified into four sedimentary systems: (1) glacial‐glaciomarine, composed of erosional surfaces, glacial troughs, furrows and draping sheets; (2) slope‐basin, formed by trough mouth fans, slope aprons, the Gebra‐Magia instability complex and turbidity systems; (3) seabed fluid outflow system composed of pockmark fields; and (4) contourite, composed of drifts and moats. The sedimentary systems show a clear zonation from shelf to basin and their dynamics reflects the complex interplay among glacial, glaciomarine, marine and oceanographic processes involved in the entire shelf‐to‐basin sediment distribution. The CBB morphology is primarily controlled by glacial/interglacial cyclicity and physiography and to a lesser extent by tectonics and oceanography. These factors have affected the South Shetland Islands (SSI) and Antarctic Peninsula (AP) margins differently, creating a relatively starved SSI margin and a more constructional AP margin. They have also created two entire sediment‐dispersal domains: the shelf‐to‐slope, which records the glaciation history of the CBB; and the lower slope‐to‐basin, which records the imprint of local factors. This study provides a ‘source‐to‐sink’ sedimentary scheme for glaciated margins, which may be applied to the basin research in other margins, based on the characterization of sedimentary systems, their boundaries and the linkages among them. This approach proves to be adequate for the identification of global and local factors governing the CBB and may therefore be applied to other study areas.     

100 Myr record of sequences, sedimentary facies and sea level change from Ocean Drilling Program onshore coreholes, US Mid-Atlantic coastal plain

We analyzed the latest Early Cretaceous to Miocene sections (～110–7 Ma) in 11 New Jersey and Delaware onshore coreholes (Ocean Drilling Program Legs 150X and 174AX). Fifteen to seventeen Late Cretaceous and 39–40 Cenozoic sequence boundaries were identified on the basis of physical and temporal breaks. Within‐sequence changes follow predictable patterns with thin transgressive and thick regressive highstand systems tracts. The few lowstands encountered provide critical constraints on the range of sea‐level fall. We estimated paleowater depths by integrating lithofacies and biofacies analyses and determined ages using integrated biostratigraphy and strontium isotopic stratigraphy. These datasets were backstripped to provide a sea‐level estimate for the past ～100 Myr. Large river systems affected New Jersey during the Cretaceous and latest Oligocene–Miocene. Facies evolved through eight depositional phases controlled by changes in accommodation, long‐term sea level, and sediment supply: (1) the Barremian–earliest Cenomanian consisted of anastomosing riverine environments associated with warm climates, high sediment supply, and high accommodation; (2) the Cenomanian–early Turonian was dominated by marine sediments with minor deltaic influence associated with long‐term (10⁷ year) sea‐level rise; (3) the late Turonian through Coniacian was dominated by alluvial and delta plain systems associated with long‐term sea‐level fall; (4) the Santonian–Campanian consisted of marine deposition under the influence of a wave‐dominated delta associated with a long‐term sea‐level rise and increased sediment supply; (5) Maastrichtian–Eocene deposition consisted primarily of starved siliciclastic, carbonate ramp shelf environments associated with very high long‐term sea level and low sediment supply; (6) the late Eocene–Oligocene was a starved siliciclastic shelf associated with moderately high sea‐level and low sediment supply; (7) late early–middle Miocene consisted of a prograding shelf under a strong wave‐dominated deltaic influence associated with major increase in sediment supply and accommodation due to local sediment loading; and (8) over the past 10 Myr, low accommodation and eroded coastal systems were associated with low long‐term sea level and low rates of sediment supply due to bypassing.     

Clinoform architecture and along‐strike facies variability through an exhumed erosional to accretionary basin margin transition

Exhumed basin margin‐scale clinothems provide important archives for understanding process interactions and reconstructing the physiography of sedimentary basins. However, studies of coeval shelf through slope to basin‐floor deposits are rarely documented, mainly due to outcrop or subsurface dataset limitations. Unit G from the Laingsburg depocentre (Karoo Basin, South Africa) is a rare example of a complete basin margin scale clinothem (>60 km long, 200 m‐high), with >10 km of depositional strike control, which allows a quasi‐3D study of a preserved shelf‐slope‐basin floor transition over a ca. 1,200 km² area. Sand‐prone, wave‐influenced topset deposits close to the shelf‐edge rollover zone can be physically mapped down dip for ca. 10 km as they thicken and transition into heterolithic foreset/slope deposits. These deposits progressively fine and thin over tens of km farther down dip into sand‐starved bottomset/basin‐floor deposits. Only a few km along strike, the coeval foreset/slope deposits are bypass‐dominated with incisional features interpreted as minor slope conduits/gullies. The margin here is steeper, more channelized and records a stepped profile with evidence of sand‐filled intraslope topography, a preserved base‐of‐slope transition zone and sand‐rich bottomset/basin‐floor deposits. Unit G is interpreted as part of a composite depositional sequence that records a change in basin margin style from an underlying incised slope with large sand‐rich basin‐floor fans to an overlying accretion‐dominated shelf with limited sand supply to the slope and basin floor. The change in margin style is accompanied with decreased clinoform height/slope and increased shelf width. This is interpreted to reflect a transition in subsidence style from regional sag, driven by dynamic topography/inherited basement configuration, to early foreland basin flexural loading. Results of this study caution against reconstructing basin margin successions from partial datasets without accounting for temporal and spatial physiographic changes, with potential implications on predictive basin evolution models.     

Role of initial depth at basin margins in sequence architecture: field examples and computer models

A delay in the onset of sedimentation during fault‐related subsidence at a basin margin can occur in both extensional settings, where footwall tilting may cause a diversion of drainage patterns, and in strike‐slip basins, where a source area may be translated along the basin margin. The ‘initial depth’ created by this delay acts as pre‐depositional accommodation and is a partly independent variable. It controls the geometry of the first stratal units deposited at the basin margin and thus modifies the response of the depositional system to subsequent, syndepositional changes in accommodation. In systems with a sharp break in the depositional profile, such as the topset edge in coarse‐grained deltas, the initial depth controls the foreset height and therefore the progradational distance of the topset edge. The topset length, in turn, influences topset accommodation during cyclical base level variations and therefore is reflected in the resulting stacking patterns at both long‐ and short‐term time scales. In the simplified cases modelled in this study, it is the relationship between the initial depth and the net increase in depth over the interval of a relative sea‐level cycle (ΔH) that governs long‐ and short‐term stacking patterns. In situations where the initial depth is significantly larger than ΔH, the topset accommodation of the first delta is insufficient to contain the volume of sediment of younger sequences formed during subsequent relative sea‐level cycles. Therefore, the depositional system tends to prograde over a number of relative sea‐level cycles before the topset area increases so that the long‐term stacking pattern changes to aggradation. Stacking patterns of high‐frequency sequences are influenced by a combination of topset accommodation available and position of the short‐term relative sea‐level cycles on the rising or falling limb of a long‐term sea‐level curve. This determines whether deposits of short‐term cycles are accommodated in delta topsets or foresets, or in both. Variations in stacking pattern caused by different initial depths may be misinterpreted as due to relative sea level or sediment supply changes and it is necessary to consider initial bathymetry in modelling and interpretation of stacking patterns, especially in fault‐bounded basins.     

Relationships between shelf‐edge trajectories and sediment dispersal along depositional dip and strike: a different approach to sequence stratigraphy

Analysis of shelf‐edge trajectories in prograding successions from offshore Norway, Brazil, Venezuela and West Africa reveals systematic changes in facies associations along the depositional dip. These changes occur in conjunction with the relative sea‐level change, sediment supply, inclination of the substratum and the relief of the margin. Flat and ascending trajectories generally result in an accumulation of fluvial and shallow marine sediments in the topset segment. Descending trajectories will generally result in erosion and bypass of the topset segment and deposition of basin floor fans. An investigation of incised valley fills reveals multiple stages of filling that can be linked to distinct phases of deepwater fan deposition and to the overall evolution of the margin. In the case of high sediment supply, like the Neogene Niger and Orinoco deltas, basin floor fans may develop systematically even under ascending trajectory styles. In traditional sequence stratigraphic thinking, this would imply the deposition of basin floor fans during a period of relative sea‐level highstand. Facies associations and sequence development also vary along the depositional strike. The width and gradient of the shelf and slope show considerable variations from south to north along the Brazilian continental margin during the Cenozoic. During the same time interval, the continental shelf may display high or low accommodation conditions, and the resulting stacking patterns and facies associations may be utilized to reconstruct palaeogeography and for prediction of lithology. Application of the trajectory concept thus reveals nuances in the rock record that would be lost by the application of traditional sequence stratigraphic work procedures. At the same time, the methodology simplifies the interpretation in that less importance is placed on interpretation and labelling of surface boundaries and systems tracts.     

Millennial and centennial variations in zircon U‐Pb ages in the quaternary indus submarine canyon

Use of deep‐water sediments in submarine fans to reconstruct changing erosion onshore is based on the premise of relatively simple transport between source and sink. However, debate continues regarding the degree of sediment buffering and recycling in the sediment transport process. In this study, we investigate the origin of sediment in the Indus Submarine Canyon since the Last Glacial Maximum (LGM; ~20 ka) using zircon U‐Pb dates. Zircon grains in the submarine canyon are resolvably different from those at the river mouth, at least before 6.6 ka, implying a disconnection between the river mouth and the canyon up to that time. Sand may be stored near the river mouth as sea level rose, while finer‐grained sediment was directly transferred into deeper water. Since 1 ka the upper canyon has shown big and rapid provenance changes, most notably a sharp increase in erosion from Nanga Parbat, whose influence is minor in the modern river. Such rapid changes imply a lack of buffering in the recent past. The modern river contrasts with sediments in the canyon in terms of its zircon U‐Pb age populations and may be influenced by significant anthropogenic impact on the terrestrial drainage basin, especially damming.     

Multi‐scale constraints of sediment source to sink systems in frontier basins: a forward stratigraphic modelling case study of the Levant region

Recent scientific work has highlighted the presence of an up to 12 km thick Cenozoic siliclastic and carbonate infill in the Levant Basin. Since the Late Eocene, several regional geodynamic events affecting Afro‐Arabia and Eurasia (collision and strike slip deformation) induced marginal uplifts. The initiation of local and long‐lived regional drainage systems in the Oligo‐Miocene period (e.g., Lebanon, Arabia and Nile) provoked a change in the depositional pattern along the Levant region from carbonate‐dominated to mixed clastic‐rich systems. Herein, we explore the importance of multi‐scale constraints (i.e., seismic, well and field data) in the quantification of subsidence history, sediment transport and deposition of a Middle to Upper Miocene “multi‐source” to sink system along the northern Levant frontier region. Through a comprehensive 4D forward stratigraphic modelling workflow, we suggest that the contribution to basin infill is split between proximal and more distal clastic sources as well as in situ carbonate and hemipelagic deposition. The results show that single‐source scenarios could not reasonably satisfy the basin‐scale constraints. The worldwide application of such new multi‐disciplinary workflows in frontier regions highlights the additional data constraints that are needed to de‐risk highly uncertain geological models in the hydrocarbon exploration phase.     

Assembling the stratigraphic record: depositional patterns and time-scales in an experimental alluvial basin

Our understanding of sedimentation in alluvial basins is best for very short and very long time‐scales (those of bedforms to bars and basinwide deposition, respectively). Between these end members, the intermediate time‐scales of stratigraphic assembly are especially hard to constrain with field data. We address these ‘mesoscale’ fluvial dynamics with data from an experimental alluvial system in a basin with a subsiding floor. Observations of experimental deposition over a range of time‐scales illustrate two important properties of alluvial systems. First, ephemeral flows are disproportionately important in basin filling. Lack of correlation between flow occupation and sedimentation indicates that channelized flows serve mainly as conduits for sediment, while most deposition occurs via short‐lived unchannelized flow events. Second, there is a characteristic time required for individual depositional events to average to basin‐scale stratal patterns. This time can be scaled in terms of the time required for a single channel‐depth of aggradation, and in this form is constant through a four‐fold variation of experimental subsidence rate.     

Impact of storms on mixed carbonate and siliciclastic shelves: insights from combined diffusive and fluid-flow transport stratigraphic forward model

A quantitative stratigraphic model of mixed carbonate/siliciclastic continental shelves is presented to investigate the relationships between depositional processes and stratigraphic responses at long‐term, large spatial scales. A diffusion model is combined with a fluid‐flow approach to simulate both long‐term factors, i.e. the processes controlling large‐scale architecture, and short‐term processes, i.e. sediment redistribution by storms. Any net sediment accumulation is the result of the succession of a storm and a fair‐weather period. Sediments are mobilized by waves and advected by low‐frequency currents during storm events. Sediments are then reworked and redistributed downslope by diffusive processes during fair‐weather period. The results are successful in capturing several major characteristics of both modern and ancient depositional systems (geometry, differential preservation, net accumulation rates). The study highlights the importance of waves and unidirectional currents. Depositional geometry and shelf morphology depend on the balance between available sediment supply (generated in situ or detrital) and the transport energy, which is related to the style of sediment transport (diffusive or advective), and to the magnitude and frequency of storms.