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.     

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.     

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.     

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.     

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 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.     

Relationships between morphological and sedimentological parameters in source‐to‐sink systems: a basis for predicting semi‐quantitative characteristics in subsurface systems

The study of source‐to‐sink systems relates long‐term variations in sediment flux to morphogenic evolution of erosional–depositional systems. These variations are caused by an intricate combination of autogenic and allogenic forcing mechanisms that operate on multiple time scales – from individual transport events to large‐scale filling of basins. In order to achieve a better understanding of how these mechanisms influence morphological characteristics on different scales, 29 submodern source‐to‐sink systems have been investigated. The study is based on measurements of morphological parameters from catchments, shelves and slopes derived from a ∼1 km global digital elevation model dataset, in combination with data on basin floor fans, sediment supply, water discharge and deposition rates derived from published literature. By comparing various morphological and sedimentological parameters within and between individual systems, a number of relationships governing system evolution and behaviour are identified. The results suggest that the amount of low‐gradient floodplain area and river channel gradient are good indicators for catchment storage potential. Catchment area and river channel length is also related to shelf area and shelf width, respectively. Similarly to the floodplain area, these parameters are important for long‐term storage of sediment on the shelf platform. Additionally, the basin floor fan area is correlative to the long‐term deposition rate and the slope length. The slope length thus proves to be a useful parameter linking proximal and distal segments in source‐to‐sink systems. The relationships observed in this study provide insight into segment scale development of source‐to‐sink systems, and an understanding of these relationships in modern systems may result in improved knowledge on internal and external development of source‐to‐sink systems over geological time scales. They also allow for the development of a set of semi‐quantitative guidelines that can be used to predict similar relationships in other systems where data from individual system segments are missing or lacking.     

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.     

Downstream Fining and Sorting of Gravel Clasts in the Braided Rivers of mid-Canterbury, New Zealand

Gravel clast size dimensions have been determined in the Rakaia, Ashburton, and Rangitata rivers by measuring 100 clasts at representative sample locations along each river. In all rivers, gravel size decreases and sorting improves downstream for mean, D₅₀, and D₉₀ fractions of the bed material. Clast size entering the sea is similar in all rivers (30–40 mm b‐axis dimension), despite large variations in transport distance, input size of clasts at their gorges, and discharge. The greatest size reduction occurs in the Rangitata River which has the shortest transport distance and steepest gradient. Rates of downstream clast size reduction are greater than would be assumed from Sternberg's Law, suggesting that additional factors, other than physical abrasion, such as sorting and selective entrainment operate.     

Sensitivity analysis of pediment development through numerical simulation and selected geospatial query

Dozens of references recognizing pediment landforms in widely varying lithologic, climatic, and tectonic settings suggest a ubiquity in pediment forming processes on mountain piedmonts worldwide. Previous modeling work illustrates the development of a unique range in arid/semiarid piedmont slope (< 0.2 or 11.3°) and regolith thickness (2–4 m) that defines pediments, despite varying the initial conditions and domain characteristics (initial regolith thickness, slope, distance from basin to crest, topographic perturbations, and boundary conditions) and process rates (fluvial sediment transport efficiency and weathering rates). This paper expands upon the sensitivity analysis through numerical simulation of pediment development in the presence of spatially varying rock type, various base level histories, various styles of sediment transport, and various rainfall rates to determine how pediment development might be restricted in certain environments. This work suggests that in landscapes characterized by soil and vegetation types that favor incisive fluvial sediment transport styles coupled with incisive base level conditions, pediment development will be disrupted by the roughening of sediment mantled surfaces, thereby creating spatial variability in topography, regolith thickness, and bedrock weathering rates. Base level incision rates that exceed the integrated sediment flux along a hillslope derived from upslope weathering and sediment transport on the order of 10^− 3 m y^− 1 restrict pediment development by fostering piedmont incision and/or wholesale removal (stripping) of regolith mantles prior to footslope pediment development. Simulations illustrate an insensitivity to alternating layers of sandstone and shale 3–15 m thick oriented in various geometric configurations (vertical, horizontal, and dip-slope) and generating different regolith hydrologic properties and exhibiting weathering rate variations up to 3-fold. Higher fluxes and residence times of subsurface groundwater in more humid environments, as well as dissolution-type weathering, lead to a thickening of regolith mantles on erosional piedmonts on the order of 10¹ m and an elimination of pediment morphology. An initial test of the model sensitivity analysis in arid/semiarid environments, for which field reconnaissance and detailed geomorphic mapping indicate the presence of pediments controlled by climatic conditions (soil hydrologic properties, vegetation characteristics, and bedrock weathering style) that are known and constant, supports our modeling results that pediments are more prevalent in hydrologically-open basins.     

Relationships Between Flow Hydraulics, Sediment Supply, Bedload Transport and Channel Stability in the Proglacial Virkisa River, Iceland

We present data from a proglacial river in Iceland that exhibits very different sedimentological characteristics when compared to its alpine counterparts. The braidplain is characterised by coarse outburst gravels that inhibit sediment transport and channel change. Bedload transport is restricted to the movement of fine-grained gravels that pass through the channel system without promoting significant changes in channel geometry. Bar forms are erosional features, inherited from the last major peak flow, rather than depositional in nature. On the basis of our observations we conclude that braidplain morphology is controlled by low frequency, high magnitude flow events, possibly associated with glacial outburst floods. This is in marked contrast to process-form relationships in more dynamic alpine proglacial channels that are characterised by high rates of sediment transport and channel change.     

Detrital zircons as palaeodrainage indicators: insights into southeastern Gondwana from Permian basins in eastern Australia

Radioisotope geochronology of detrital grains coupled with quantitative classification of grain morphology can provide valuable insight into the history of sediment transportation and recycling. Here we present ca. 750 new concordant U‐Pb ages from detrital zircon grains from a relatively understudied Permian sedimentary succession in the New England Orogen (eastern Australia), coupled with values of abrasion that provides a proxy for the relative source‐to‐sink distance. We show that cumulative proportion curves for age groups that correspond to plausible source regions provide insights into the palaeodrainage, even if the basin stratigraphy is relatively poorly constrained. This approach is particularly suitable for investigating complex depositional systems that received inflow from different provenance, such as back‐arc and intra‐cratonic basins. Using the example from eastern Australia, our results show that during the Early Permian, a large regional fluvial system transported detritus from continental Gondwana across the landscape of the former active continental margin (New England Orogen) and the simultaneously developing East Australian Rift System. In addition, a local drainage system mobilised detritus within the New England Orogen. Our new constraints for the Early Permian palaeogeography support the idea that the Lower Permian successions of the southern New England Orogen were deposited in a back‐arc region that was likely linked to a retreating subduction zone.     

Axial and transverse deep-water sediment supply to syn-rift fault terraces: Insights from the West Xylokastro Fault Block,Gulf of Corinth,Greece

Deep-water syn-rift systems develop in partially- or transiently-linked depocentres to form complicated depositional architectures, which are characterised by short transport distances, coarse grain sizes and a wide range of sedimentary processes. Exhumed systems that can help to constrain the tectono-stratigraphic evolution of such systems are rare or complicated by inversion tectonics. Here, we document a mid-Pleistocene deep-water syn-rift system fed by Gilbert-type fan deltas in the hangingwall of a rift margin fault bounding the West Xylokastro Horst block, on the southern margin of the Gulf of Corinth, Greece. Structural and stratigraphic mapping combined with digital outcrop models permit observations along this syn-rift depositional system from hinterland source to deep-water sink. The West Xylokastro Fault hangingwall is filled by two distinct sediment systems; an axial system fed by coarse-grained sediment gravity flows derived from fault-tip Gilbert-type fan deltas and a lateral system dominated by mass transport deposits fed from an evolving fault-scarp apron. Abrupt changes in stratigraphic architecture across the axial system are interpreted to record changes in relative base level, sediment supply and tectonics. Locally, depositional topography and intra-basinal structures controlled sediment dispersal patterns, from bed-scale infilling of local rugose topography above mass transport complexes, to basin-scale confinement from the fault scarp apron. These acted to generate a temporally and spatially variable, heterogeneous stratigraphic architecture throughout the basin-fill. The transition of the locus of sedimentation from a rift margin to a fault terrace through the syn-sedimentary growth of a basinward fault produced regressive surfaces updip, which manifest themselves as channels in the deep-water realm and acted to prograde the system. We present a new conceptual model that recognises coeval axial and transverse systems based on the stratigraphic architecture around the West Xylokastro fault block that emphasizes the lateral and vertical heterogeneity of rift basin-fills with multiple entry points.     

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.     

基于数字图像的中国西北地区戈壁表面砾石形貌特征研究

中国戈壁面积约66.08万km²,超过了流动沙丘和半固定沙丘的面积之和,但目前对戈壁沉积特征的研究程度相对较低。本文采用ImageJ软件,对中国西北地区戈壁原位无干扰的表面数字图像进行量算,获取了砾石覆盖度、粒径、磨圆度和形状比率等形貌参数。结果表明：中国西北地区戈壁表面的砾石覆盖度介于31.5%～84.6%,以中覆盖度为主,70%的戈壁属于空气动力学稳定表面;90%以上的戈壁表面砾石平均粒径为细砾和中砾。不同区域戈壁表面砾石磨圆度的平均值介于0.50～0.76,形状比率变化范围在1.38～2.46。戈壁表面砾石形貌特征与其成因类型密切相关：以剥蚀（侵蚀）-洪积作用为主形成的戈壁,砾石粒径较粗、形态比率较大、磨圆度低、覆盖度较高;以冲洪积为主形成的戈壁,砾石粒径和形态比率变小,磨圆度变好而覆盖度降低。砾石形貌特征可为追溯戈壁物源区和反演沉积物的搬运堆积过程提供参考。     

Time lag of syntectonic sedimentation across an alluvial basin: theory and example from the Ebro Basin, Spain

We propose and test a conceptual framework for evaluating the relative timing of different types of sedimentary indicators of tectonism in alluvial foreland basin settings. We take the first occurrence of a detrital grain from a newly exposed source‐area lithology to provide the best indicator of the onset of tectonic uplift in the source area. Source‐area unroofing may lag behind initial uplift because of the type, thickness and structure of rocks in the uplifted mountain block, drainage patterns and climate. However, once exposed, advective transport disperses grains quickly throughout fluvial systems. Because of increased subsidence rate from thrust belt loading, an increase in sedimentation rate begins coincident with tectonic load emplacement within the flexural half‐width of the basin. However, farther out into the basin increased sedimentation rates lag behind the composition signal because of time lags associated with propagation of the thrust load and attendant sediment loads into the basin. The progradation of syntectonic gravel lags behind all of these signals as a direct function of the relative proportion of gravel fraction within transported sediment and rates and geometry of subsidence, which selectively traps the coarsest grain‐size fractions in the most proximal parts of the basin. We demonstrate this signal attenuation in the syntectonic Horta–Gandesa alluvial system (late Eocene–Oligocene), exposed along the southeast margin of the Ebro Basin, Spain. The results demonstrate that: (1) the time spans between the compositional signal and the progradation of the gravel front can be geologically significant, on the order of more than a million years within as little as 20 km of the thrust front; and (2) time lags between the signals increase with distance away from the deformation front. No lag time was observed between the first appearance of a new clast composition and the arrival of gravel front when the thrust front was within a few tens of metres from the depositional site. In contrast, the time lag was 0.5–1 Myr when the thrust front was about 5–6 km away and it increased to >1 Myr when the deformation front was about 8 km away. At the most extreme position, when the thrust front was 15–20 km away, the gravel front never reached the study area.     

Changeability of Movable Bed‐Surface Particles in Natural,Gravel‐Bed Channels and Its Relation to Bedload Grain Size Distribution (Scott River,Svalbard)

The presented paper analyses the variability of grain size distribution parameters of bedload transported by the gravel‐bed Scott River (Svalbard) draining a glacier catchment with an area of 10 km². The grain size distribution analysis is one of the basic elements of identification of the fluvial transport mechanisms in gravel‐bed rivers. It is used for the determination of threshold values for bedload movement. It is also treated as an important indicator of the origin, routes of distribution, and conditions of transport and deposition of fluvial bedload. The field study in a natural proglacial gravel‐bed channel was carried out at two reaches in the mouth section of Scott River. The study revealed relatively high temporal variability and similar mean parameters of grain size distribution in conditions of low discharges. Bedload transport rates reached a mean of 71.9–76.0 kg d^?1 in channel cross‐section. Bedload texture was dominated by gravels with a proportional contribution of the fine‐grained fraction along with very fine‐grained gravels (8‐2 mm) of 38.8%. The medium‐grained fraction (16‐8 mm) constituted 33.7%, with a lower contribution from the coarse‐grained fraction (32‐16 mm) of 23.2%, and the very coarse‐grained fraction (64‐32 mm) of 4.4%. Two periods in the course of bedload transport and distribution of grain size distribution parameters were distinguished based on variation of hydro‐meteorological conditions. The first half of the measurement period was distinguished by significantly higher values of daily loads and increased contribution of the coarse‐grained and very coarse‐grained fraction (28–31% and 6.2–6.6%, respectively). During this time, the river discharged up to 94% of bedload. This resulted in a clear tendency for riverbed scouring. The second half was distinguished by generally low daily bedload transport rates (<10 kg d^?1), an increase in contribution of fine‐ and very fine‐grained gravels (42–55.6%), and a change in the tendency to aggradation. Grain size indices were more varied, and grains were usually finer and better sorted. Selective transport processes, often related to redeposition, were dominant in the channel. Along with an increase in flow velocity, conditions for material deposition became more variable. This was manifested in weaker sorting and an increase in grain diameter.     

Relationships between tectonic activity and sedimentary source-to-sink system parameters in a lacustrine rift basin: A quantitative case study of the Huanghekou Depression (Bohai Bay Basin,E China)

Lacustrine rift basins commonly preserve a fairly complete record of the sediment source-to-sink (S2S) system, and consequently may form an ideal natural laboratory for establishing quantitative relationships between the various elements within the S2S system. The tectonic-activity rate in the source (e.g., fault-growth rate and fault-activity rate), accommodation space and depositional system in the sink (e.g., areal extent and volume, as well as the depositional dip of the fan- and braid-deltas) are genetically related and their quantitative correlations are explored. The Palaeogene succession on the southwestern margin of the Huanghekou Depressionin the Bohai Bay Basin, one of the largest lacustrine rift basins in eastern China, was chosen to study these relationships, using 3-D seismic, core and well-log data. The tectonic activity was strongly related to the sediment supply, accommodation space and morphology of the sink area. Three different rates of tectonic activity are identified; these led to changes in the basic features of the S2S system that influenced each other. In Members 4 and 3 (lower unit) of the Shahejie Fm. (40.44–44.7 Ma), strong tectonic activity led to significant uplift, resulting in the widest exposure of the provenance area to erosion, to a high sediment-supply rate, to a steep slope and to a large accommodation space which controlled the development of several fan-deltas with steep progradational angles. In Member 3 (upper unit) of Shahejie Fm. (37.89–40.44 Ma) and Member 3 of Dongying Fm. (30.2–33.28 Ma), decreased tectonic activity led to slower uplifting, resulting in a wider alluvial plain, longer transport distances, a lower sediment-supply rate and less accommodation space, so that braid-deltas with larger volumes and a gentler slope developed; In Members 1 and 2 of Shahejie Fm. (33.28–37.89 Ma) and Member 2 of Dongying Fm. (26.71–30.2 Ma), still further decreasing tectonic activity led to a still lower sediment-supply rate, a more gentle depositional slope, less accommodation space, and the development of several braid-deltas with a gentle angle. The quantitative relationships established here advance our understanding of the relationships within lacustrine source-to-sink systems, especially for tectonically controlled rift basins.     

Magnetostratigraphy,age and depositional environment of the Lobo Formation,southwest New Mexico: implications for the Laramide orogeny in the southern Rocky Mountains

The Lobo Formation of southwestern New Mexico consists of spatially variable continental successions attributed to the Laramide orogeny (80–40 Myr), although its age and provenance are virtually undocumented. This study combines sedimentological, magnetostratigraphical and geochronological data to infer the timing and origin of the Lobo Formation. Measured sections of Lobo strata at two locations, Capitol Dome in the Florida Mountains and in the Victorio Mountains, indicate significant differences in depositional environments and sediment provenance. At Capitol Dome, where Lobo strata were deposited above a syncline developed in Palaeozoic strata, deposition took place in fluvial, palustrine and marginal lacustrine settings, with alluvial‐fan deposits only at the top of the formation. Combined magnetostratigraphy and a young U–Pb detrital zircon age suggest deposition of the section at Capitol Dome from ~60 to 52 Ma. The Lobo Formation in the Victorio Mountains was deposited in alluvial‐fan and fluvial settings; the age of deposition is poorly bracketed between 66 ± 2 Ma, the weighted‐mean age of two young zircons, and middle Eocene (~40 Ma), the approximate age of overlying volcanic rocks. U–Pb zircon ages from sandstones at the Victorio and Capitol Dome localities indicate that different source rocks provided sediment to the Lobo Formation. Local Proterozoic basement (~1.47–1.45 Ga) dominated the source of the Lobo Formation in the Victorio Mountains, consistent with abundant granitic clasts that are present in the proximal facies there; a diverse range of grain ages suggest that recycled Lower Cretaceous strata provided the dominant source for Lobo Formation sediment at the Capitol Dome locality. The U–Pb data suggest that the depositional systems at the two sites were not connected. Contrasts in depositional setting and detrital zircon provenance indicate that the Palaeogene Lobo Formation in southwest New Mexico was deposited in an assemblage of local depositional settings, possibly in separate structural basins, as a consequence of Laramide tectonics in the region.     

Structural controls on the stratigraphic architecture of net‐transgressive shallow‐marine strata in a salt‐influenced rift basin: Middle‐to‐Upper Jurassic Egersund Basin,Norwegian North Sea

In this study, we integrate 3D seismic reflection, wireline log, biostratigraphic and core data from the Egersund Basin, Norwegian North Sea to determine the impact of syn‐depositional salt movement and associated growth faulting on the sedimentology and stratigraphic architecture of the Middle‐to‐Upper Jurassic, net‐transgressive, syn‐rift succession. Borehole data indicate that Middle‐to‐Upper Jurassic strata consist of low‐energy, wave‐dominated offshore and shoreface deposits and coal‐bearing coastal‐plain deposits. These deposits are arranged in four parasequences that are aggradationally to retrogradationally stacked to form a net‐transgressive succession that is up to 150‐m thick, at least 20 km in depositional strike (SW‐NE) extent, and >70 km in depositional dip (NW‐SE) extent. In this rift‐margin location, changes in thickness but not facies are noted across active salt structures. Abrupt facies changes, from shoreface sandstones to offshore mudstones, only occur across large displacement, basement‐involved normal faults. Comparisons to other tectonically active salt‐influenced basins suggest that facies changes across syn‐depositional salt structures are observed only where expansion indices are >2. Subsidence between salt walls resulted in local preservation of coastal‐plain deposits that cap shoreface parasequences, which were locally removed by transgressive erosion in adjacent areas of lower subsidence. The depositional dip that characterizes the Egersund Basin is unusual and likely resulted from its marginal location within the evolving North Sea rift and an extra‐basinal sediment supply from the Norwegian mainland.