Channel Sinuosity Research Articles

Architecture and geomorphology of fluvial channel systems in the Arabian Basin

The architecture and geomorphology of fluvial channel system plays an important role in the interpretation of its sedimentary processes and characterization of the ability for subsurface storage. In the Arabian Basin, this system is considered a new petroleum play after a century of carbonate-play dominance with enormous petroleum reserves. In addition, the presence of publicly available 3D seismic refection data in the Arabian Basin is very limited, providing a condition that fluvial channel system knowledge becomes publicly less understood. Therefore, our study utilizes 3D seismic reflection data and aims to (1) interpret seismic facies and architecture, (2) map the unit thickness and lateral distribution, and (3) calculate morphometry of the Late Carboniferous to Early Permian fluvial channel systems in the Arabian Basin, and discuss its sedimentary processes, development and petroleum prospectivity. Seismic facies and seismic attribute analysis revealed three distinct fluvial channel systems including their crevasse-splay and flood plain. The channels are characterized by isolated bright on the RMS amplitudes, spectral decomposition, variance and sweetness with sinuous geomorphology and lobes (crevasse-splay) and variation of amplitude values in hummocky to sub-parallel and parallel (flood plain) reflection configuration. The morphometric analysis shows three clusters on the scaling relationship between maximum channel width and meander belt width, as well as the minor variation on the channel sinuosity index. These results indicated the dominance of the bed-load sediment transport mechanism in the fluvial depositional environment with a single-story channel body architecture. These factors provide the ability for fluvial channel systems in the studied area to act as petroleum reservoir as well as potential source rock, cap rock and stratigraphic traps. Furthermore, a single-story channel body indicated poorly connected among them, both in lateral and vertical extends that required horizontal wellbore for drainage the reservoir. Our study revealed that fluvial channel systems in the Arabian Basin has potentiality both in petroleum prospectivity as well as subsurface storage (carbon dioxide, waste, hydrogen). In addition, the workflow presented here could be applicable to characterize the fluvial channel system from 3D seismic reflection data in other basins, worldwide.

Modeling the Tilt of Bend‐Traversing Turbidity Currents: Implications for Sinuous Submarine Channel Development

AbstractThe controls on the development of submarine channel sinuosity are contested: slope gradient and Coriolis forcing have both been recognized as key governing factors: gradient via an inverse relationship (low sinuosity at high slope and vice versa), and Coriolis forcing through its effect on sedimentation patterns (reducing lateral bend migration, and hence sinuosity development, at high latitudes and/or in large channels). Using theoretical models to calculate the bulk properties of channelized turbidity currents, this study investigates the joint role of the Coriolis force and parameters including channel size, downchannel slope and turbidity current properties in the development of submarine channel sinuosity. Model validation is undertaken through the comparison of the calculated turbidity current tilting against the measured tilting of channel levees in the Northwest Atlantic Mid‐Ocean Channel; this approach is then used to evaluate the controls on channel sinuosity in nine other modern seafloor channels. The results indicate that the Coriolis force only becomes significant when the size of the channel, the slope gradient and flow conditions are within appropriate ranges instead of solely being dependent on latitude. Thus, thick and dense (≥1% bulk sediment concentration) flows traveling within steep‐gradient, small‐scale channels were shown to be relatively less susceptible to flow modification by Coriolis forcing even at high latitudes. On the other hand, thin and dilute (≪1% bulk sediment concentration) flows in shallow‐gradient, large‐scale channels showed susceptibility to Coriolis forcing at all latitudes. These results offer new insights into submarine channel evolution and intra‐channel sedimentation patterns.

Channel Sinuosity Effects on Inland Transport in the Riverine Region of Ilaje, Nigeria

Transportation is an essential tool for regional social and economic growth, as well as national development. Transport has a vital social and environmental impact that cannot be overlooked. The character of naturally functioning rivers varies greatly and does not remain constant since it is mainly determined by several of physical factors and processes, among which is river sinuosity. Understanding how the inland waterways change with time and the effect or consequences of these changes on the lifestyle and economic activities of the inhabitants becomes very important. This study focused on revealing the changes that had occurred in the planforms of Igbokoda-Idiogba/Ayetoro waterways in Ilaje, Ondo state; its effects on inland transport taking cognisance of sinuosity index. It assessed morphological changes of navigable rivers in the study area from 1972-2022; the effects of river sinuosity on inland transport in the study area were considered. The study deployed geospatial techniques to assess the decadal changes of changing patterns of the channel’s sinuosity taking cognizance of the sinuosity index and formula. However, the study shows the capabilities of geospatial techniques in monitoring river morphology. The study revealed significant changes in the channel’s sinuosity and consequential effects of the changes. Sustainable transport measures for safety and efficiency were recommended.

Neotectonic impact on drainage development in the Eastern Himalayan foreland basin

The present study intends to divulge the complex drainage evolution in connection to neotectonic controls focusing the Jaldhaka and Raidak River interfluve on the eastern Himalayan Foreland Basin (HFB). It involves analysing the surface and sub-surface changes in the fluvial system's evolution with field and geospatial evidence bearing geomorphic markers, sediment analogy and channel morphological properties. The channel orientation, planimetry and the channel longitudinal process anomaly were attributed solely from the geospatial perspective as surface evidence of neotectonic controls. The results unveil an intense neotectonic control on channel development–from structurally guided channel avulsion that shaped the presently active course of the Torsa River to deformation-guided channel morphological changes. Moreover, relatively higher deflection angles, intense channel sinuosity and tight meandering bends forming along the structural elements symptomizes the structure-controlled drainage development in recent times. Furthermore, sediment analogy from deep well logs and shallow subsurface trenches was analysed to obtain subsidence-driven fluvial sequences and geochronology of sedimentary deformation in channel beds and floodplains. The Optically Stimulated Luminescence (with fading correction) technique-based determination of shallow sub-surface sediment's age indicates occurrences of palaeoseismic events between 1.6 ka (±0.1 ka) and 1.35 ka (±0.2 ka) as well as between 1.35 ka (±0.2 ka) and 1.14 ka (±0.1 ka) had resulted in channel bed sagging while stress impacted the formation of syn-sedimentary folding. The palaeoseismic events that led to relative subsidence are evident in upward sediment stacking (channel fill) sequences being observed at multiple trenches. The deep sub-surface staking of channel floor deposition lenses is also evident of basin subsidence that influenced channel oscillations of reoccupation type.

Reach scale channel planform dynamics of transboundary River Jaldhaka within Himalayan Foreland Basin

ABSTRACT The slopes of Himalayan piedmont and foothill plain are being modified by the Himalayan origin river systems. In this study, spatiotemporal dynamics of channel planform of braided River Jaldhaka have been estimated using United States Army Map (1956) and landsat satellite images (1980-MSS, 1990-TM, 2000-TM, 2010-ETM+ and 2022-OLI) for the delineation of banklines, channel length, sinuosity index, braiding index, channel widths, identification of partial channel avulsion sites and bankline migration using Digital Shoreline Assessment System (DSAS) toolbar. Linear Regression Rate, Net Bankline Movement and End Point Rate were also calculated. Results revealed that the lower reach is more sinuous (maximum average channel sinuosity 1.65) compared with reach-I (1.29) and II (1.11)). The maximum channel width was in the year 2022 (968.6 m) and minimum average channel width was in 1956 (239.87 m). The maximum BI value (3.55) has been calculated in the sub reach-2 (SR-2, reach-I). Similarly, DSAS output shows maximum average EPR values (6.43 m/year) in lower reach which was most erosion prone bank. Bank facies study showed that non-cohesive bank materials accelerate rapid rate of channel avulsion and bank erosion. The variation of discharge, velocity, presence of vegetation and anthropogenic interventions controls the nature of planform changes of Jaldhaka River.

Application of Oversampling Techniques for Enhanced Transverse Dispersion Coefficient Estimation Performance Using Machine Learning Regression

The advection–dispersion equation has been widely used to analyze the intermediate field mixing of pollutants in natural streams. The dispersion coefficient, manipulating the dispersion term of the advection–dispersion equation, is a crucial parameter in predicting the transport distance and contaminated area in the water body. In this study, the transverse dispersion coefficient was estimated using machine learning regression methods applied to oversampled datasets. Previous research datasets used for this estimation were biased toward width-to-depth ratio (W/H) values ≤ 50, potentially leading to inaccuracies in estimating the transverse dispersion coefficient for datasets with W/H > 50. To address this issue, four oversampling techniques were employed to augment the dataset with W/H > 50, thereby mitigating the dataset’s imbalance. The estimation results obtained from data resampling with nonlinear regression method demonstrated improved prediction accuracy compared to the pre-oversampling results. Notably, the combination of adaptive synthetic sampling (ADASYN) and eXtreme Gradient Boosting regression (XGBoost) exhibited improved accuracy compared to other combinations of oversampling techniques and nonlinear regression methods. Through the combined ADASYN–XGBoost approach, it is possible to enhance the transverse dispersion coefficient estimation performance using only two variables, W/H and bed friction effects (U/U*), without adding channel sinuosity; this represents the effects of secondary currents.

Temporal change in channel form and hydraulic behaviour of a tropical river due to natural forcing and anthropogenic interventions

ABSTRACT Assessing the degradation of river channels is crucial in the Anthropocene era, particularly in the deltaic areas worldwide. The present study aims to investigate the degradation of the Mathabhanga-Churni River giving emphasis on the temporal change of channel morphology and hydraulic behaviour and comparing the current situation with the historical past based on planform morphology and meander geometry of 118 meander loops, and width, depth, cross-sectional area, and hydraulic behaviour (velocity, discharge, stream power) at 47 cross-sections. The absence of lateral dynamicity, the static character of channel sinuosity during the last century (1913–2018), and the constant meander morphology reflects the static meander geometry and degradation of the river. The reduction of average channel width, depth, and cross-sectional area supports the falling trend of channel forms. Findings on hydraulic behaviour indicate declining discharge (~50% reduction during 1915–2018) that induces the present-day downscaled velocity and lowered stream power. Neotectonics (eastward tilting of the Bengal delta) and anthropogenic stressors such as stream crossings, agriculture on river beds, brickfields, and urbanisation have a severe impact on the hydromorphology of the channel, turning the active river into a stagnant and polluted channel.

Limited Evidence of Late Quaternary Tectonic Surface Deformation in the Eastern Tennessee Seismic Zone, United States

ABSTRACT The ∼300-km-long eastern Tennessee seismic zone, United States, is the secondmost seismically active region east of the Rocky Mountains. Seismicity generally occurs below the Paleozoic fold-and-thrust belt within the Mesoproterozoic basement, at depths of 5–26 km, and earthquake magnitudes during the instrumental record have been moment magnitude (Mw) ≤4.8. Evidence of surface deformation may not exist or be difficult to detect because of the vegetated and soil-mantled landscape, landslides, locally steep topography, anthropogenic landscape modification, or long, irregular recurrence intervals between surface-rupturing earthquakes. Despite the deep seismicity, analog models indicate that accumulation of strike-slip or oblique-slip displacement at depth could be expected to propagate upward through the Paleozoic section, producing a detectable surficial signal of distributed faulting. To identify potential surface deformation, we interrogated the landscape at different spatial scales. We evaluated morphotectonic and channel metrics, such as channel sinuosity and catchment-scale hypsometry. In addition, we mapped possible fault-related topographic features on 1-m lidar data. Finally, we integrated our observations with available bedrock and Quaternary surficial mapping and subsurface geophysical data. At a regional scale, most morphotectonic and channel metrics have a strong lithologic control. Within smaller regions of similar lithology, we observe changes in landscape metrics like channel sinuosity and catchment-scale hypsometry that spatially correlate with new lineaments identified in this study and previously mapped east–west Cenozoic faults. These faults have apparent left-lateral offsets, are optimally oriented to slip in the current stress field, and match kinematics from the recent focal mechanisms, but do not clearly preserve evidence of late Pleistocene or Holocene tectonic surface deformation. Most newly mapped lineaments might be explained by either tectonic or nontectonic origins, such as fluvial or karst processes. We also reevaluated a previously described paleoseismic site and interpret that the exposure does not record evidence of late Pleistocene faulting but instead is explained by fluvial stratigraphy.

Timescale of the Morphodynamic Feedback Between Planform Geometry and Lateral Migration of Meandering Rivers

AbstractAcross varied environments, meandering channels evolve through a common morphodynamic feedback: the sinuous channel shape causes spatial variations in boundary shear stress, which cause lateral migration rates to vary along a meander bend and change the shape of the channel. This feedback is embedded in all conceptual models of meandering channel migration, and in numerical models, it occurs over an explicit timescale (i.e., the model time step). However, the sensitivity of modeled channel trajectory to the time step is unknown. In numerical experiments using a curvature‐driven model of channel migration, we find that channel trajectories are consistent over time if the channel migrates ≤10% of the channel width over the feedback timescale. In contrast, channel trajectories diverge if the time step causes migration to exceed this threshold, due to the instability in the co‐evolution of channel curvature and migration rate. The divergence of channel trajectories accumulates with the total run time. Application to hindcasting of channel migration for 10 natural rivers from the continental US and the Amazon River basin shows that the sensitivity of modeled channel trajectories to the time step is greatest at low (near‐unity) channel sinuosity. A time step exceeding the criterion causes over‐prediction of the width of the channel belt developed over millennial timescales. These findings establish a geometric constraint for predicting channel migration in landscape evolution models for lowland alluvial rivers, upland channels coupled to hillslopes and submarine channels shaped by turbidity currents, over timescales from years to millennia.

Assessment of On-going tectonic deformation in the Goriganga River Basin, Eastern Kumaon Himalaya Using Geospatial Technology

The Goriganga river basin lies in the Northeast Kumaon Himalaya and is found suitable for assessing active tectonics at different scales. In addition, this study focuses on the assessment of ongoing tectonic activity through morphotectonic measurement of the Goriganga river basin, which is an ideal location for such analysis and Goriganga river basin transects with three major domains of Himalaya’s lithotectonic structures viz., Tethys, Vaikrita, and Lesser Himalayan Domain. To realize this task, the ASTER Digital Elevation Model was used and found suitable to extract different morphotectonic indices such as Stream Length Gradient (SL), Hypsometric Integral (HI), Length of Overland Flow (Lg), Drainage Density (Dd) and Channel Sinuosity (Cs). Results of these important indices, including SL (18- 4737) HI (0.26- 0.57), and Lg (0.08- 0.19) depict greater variability in the tectonics activity while these values are correspondingly high in the close proximity of lithotectonic units, showing strong tectonic activity. In the extreme south, the Rauntis Gad basin strongly influences tectonism due to transecting syncline and anticline as well as unknown active faults.

Morphotectonic assessment of the Gaula river basin, Kumaun lesser Himalaya, Uttarakhand

Morphotectonics is a discipline of geomorphology that explores how landforms are formed or modified by tectonic action. In the present study we uthe sed application of geospatial technology to evaluate the active deformation owing to Main Boundary Thrust (MBT) and Ramgarh Thrust (RT) in Outer part of Kumaun Lesser Himalaya. Active deformation inside river valleys is ascribed downcuttinging and incision of bedrock, offset of river channel, lateral migration of the river, and development of Knickpoints. Therefore, we used quantitative geo-mathematical analysis of The Gaula river basin using ASTER DEM along with survey of India Toposheet (1:50,000) supplemented by field observations. Four morphotectonic metrics, including the basin elongation ratio, the asymmetry factor, the channel sinuosity, and the hypsometric integral, were derived to examine the relative index of active tectonics (RIAT). We applied Stream Power Incision Model (SPIM) by analysing the steepness index (Ksn) using the stream power law. Additionally, a comprehensive evaluation of tributary streams of the Gaula watershed has been carried out to understand relative tectonic activity. Further we used Chi integral (χ) to measure transience dynamics and geometric disequilibrium of Gaula basin. We conclude that most sub-basins are tectonically enhanced, structurally organized and elongated in nature. The landform in the study area is largely controlled by presence of MBT, RT and subsidiary thrusts spread over in the vicinity. Based on our activity classes we concluded that approximately 31% of the area in Gaula river basin falls in very active whereas ∼34% is potentially active. Furthermore, we suggest that the results will be very useful for estimation of hazard potential zones in sub-Himalayan region of foothill zone of Kumaun Himalaya.

Fluvial-style migration controls autogenic aggradation in submarine channels: Joshua Channel, eastern Gulf of Mexico

Abstract There has been debate over the processes acting on deep-water channels, with comparisons made to the evolution of meandering fluvial systems. We characterized a three-dimensional seismic-reflection dataset of the Joshua deep-water channel–levee system located in the eastern Gulf of Mexico and interpreted 13 horizons showing its kinematic evolution over a 25 km reach. Over this reach, we documented channel migration through systematic bend expansion and downstream translation, which was sustained through channel aggradation as sinuosity increased from 1.25 to 2.3 at abandonment. An abrupt decrease in sinuosity was associated with a neck cutoff, which changed the subsequent migration direction of the channel in that locality. These processes are analogous to the evolution of meandering fluvial systems. We show that increasing channel sinuosity correlates to a reduction in channel slope and hypothesize that this promoted increasingly depositional turbidity currents that led to channel aggradation. Using a simple forward stratigraphic model in which vertical movements of the channel are governed by a stream power law, we show how aggradation can be driven autogenically. Trends in sinuosity, aggradation and slope are in broad agreement between the Joshua Channel and the model. This highlights the potential importance of intrinsic channel processes as a control on system evolution.

Historical disconnection from floodplain alters riparian forest composition, tree growth and deadwood amount

Riparian forests are among the most dynamic but threatened terrestrial ecosystems. Their dynamism and conservation depend on historical changes in river geomorphology, which can be evaluated through changes in channel sinuosity. However, we lack long-term assessments on sinuosity and how they impact riparian forest composition, tree growth and deadwood amount. To fill this research gap, we reconstructed river sinuosity in 14 sites across the middle Ebro basin, north-eastern Spain, using historical aerial photographs taken in 1927, 1956, 1998–2003 and 2014–2015. Relationships between sinuosity, stand composition and deadwood amount and decay degree were calculated. We also reconstructed radial growth of the major tree species (Populus alba, Populus nigra, Fraxinus angustifolia, Salix alba and Ulmus minor) in two sites to evaluate how coupled it was with changes in river flow after dam building. From 1927 to 2015, sinuosity decreased passing from 1.39 to 1.20. The river dynamics were altered in the 1950s and 1960s after dam and dyke building. Sites with high sinuosity values in 1956 corresponded to mature stands with large P. nigra individuals. Sinuosity was negatively related to F. angustifolia (rs = −0.83, p < 0.001) and P. alba (rs = −0.64, p = 0.02) abundance, whereas sites dominated by P. alba and U. minor presented abundant decayed deadwood. A loss of sinuosity and a contraction of the riverbank gradient increased disconnection of active channel from floodplain, with a mixing of more (e.g., P. nigra) and less phreatophytic species (e.g., U. minor). River flow diversion reduced growth and increased the tree-to-tree P. alba growth coherence. Hydrological droughts contributed to growth decline and dieback of U. minor, which is sensitive to spring river flow. Conservation and restoration of riparian forests must consider historical changes in river geomorphology related to human activities.

The Igarapé Weir decelerated transport of contaminated sediment in the Paraopeba River after the failure of the B1 tailings dam (Brumadinho)

The B1 dam of Córrego do Feijão Mine, owned by Vale, S.A. mining company and located on the Ferro-Carvão stream, collapsed and injected 2.8 Mm3 of clayey, silty, and sandy iron- and manganese-rich tailings into the Paraopeba River (Minas Gerais state, Brazil). The accident occurred on 25 January 2019 and the tailings have been co-transported with coarser natural sediment since then, being partly trapped in the Igarapé Weir reservoir located on the Paraopeba River nearly 45 km downstream the injection point. The general purpose of the current study was to model suspended sediment transport in the vicinity of the Igarapé Weir aiming to assess the concomitant barrier effect imposed by this structure. Specifically, the spatial distributions of suspended clay, silt, and very fine-grained sand fractions (CSS) of sediment were mapped around the Igarapé Weir under low-flow (16 m3/s) and high-flow (5 to 10,000 years return period stream discharge; 699–2,699 m3/s) regimes, using RiverFlow2D as the modelling tool. The concentrations of the various grain materials in the upstream and downstream sectors were quantified linking the barrier effect to concentration reductions in the direction of stream flow. It was also a study goal to calculate differences of iron and manganese concentrations in the sediment + tailings mixtures along the Paraopeba River. The study results showed reductions in the CSS between 6.6% and 18%, from upstream to downstream of the Igarapé Weir, related with backwater effects, free and submerged hydraulic jumps, bank sedimentation in periods of high flow, and streambed sedimentation controlled by channel sinuosity and tailings density. These reductions were accompanied by drops in the concentrations of iron and manganese present in the clay and silt fractions, which varied between 6% and 42% under low flows and between 16% and 44% under high flows. Bank sedimentation was viewed as a potential threat to the riparian vegetation in the long-term. Dredging is the potentially most effective mitigation measure to help lead the Paraopeba River to a pre-rupture condition. The retention of sediment + tailings transported in suspension is less effective than the trapping of bedload sediment + tailings behind the Igarapé weir. The efficacy of sediment trapping is expected to be larger for natural sediment because it is much coarser than the tailings. In that context, the simulations revealed for the low-flow period that 33.6% of the sediment deposition comprised suspended transport of natural sediment (thus, was comprised 66.4% of bedload transport), this proportion rose to 86.9% for mixtures of natural sediment + tailings, a result that did not differ much for the high-flow periods.

Contribution of GIS to Hydromorphometric Characterization of the Nkoup Watershed (Nun Plain-Cameroon)

The Nkoup watershed (10°35’-10°47’E and 5°27’-5°42’N) is a volcanic zone situated in Nun Plain West Cameroon. The high fertility of the soils makes it a strategic agropastoral area where water resources are heavily exploited and used for several purposes. Due to human activities, soils and water resources are deteriorating, giving birth to water pollution and hydromorphological hazards. This work aims to determine the hydromorphometric parameters of the Nkoup watershed so that the data obtained help in the sustainable management of water resources and conservation of soil. To achieve this aim, various data were collected from DEM dataset derived from SRTM and processed in specialized software (QGIS and ArGIS). The simplified hydrological balance was calculated using the upstream approach. The Nkoup watershed has: Axial length Lax = 25.8 km, Axial Width Wax = 11.1 km, Perimeter P = 132.6 km, Area A = 173.7 km2 , Average Altitude Ha = 1726.3 m, Compactness Index Icomp = 2.8, Relief ratio Rr = 3.9 m/km, Circularity ratio Rc = 0.1, Elongation ratio R = 0.1, Drainage texture ratio Rt = 0.6, Drainage density Dd = 0.5 km/km2 . Stream Frequency Fs = 0.4, Channel Sinuosity Index CSI = 0.8, Stream gradient Sg = 0.6 and global slope Index Ig = 6.8 m/km. The specific height Difference Ds = 89.4 m shows moderate relief. The precipitation and evapotranspiration are unevenly distributed. With P = 187.7 mm/an, ETP = 953.4 mm/an, Q = 4.2 m3 /s, R = 762.5 mm/an, ETR = 832.3 mm/an and I = 282.9 mm/an. The Nkoup, 36.9 km long, has a sinuous aspect due to the low slope and the high CSI. The piezometric levels vary according to the seasons and the groundwater flow follows the N-S direction as surface flow.

The delta-fluvial evolution of a lacustrine basin with gentle slope and low sedimentation rate: A case study of the Fudong Slope, Junggar Basin, Northwest China

Gentle slope belts of lacustrine basins are important areas for the generation of stratigraphic petroleum reservoirs controlled by sedimentary systems. Based on coring, well logging, 3D seismic and analytical test data, the sedimentary system and sandbody distribution characteristics of the Jurassic Toutunhe Formation (J2t) in the Fudong slope of the Junggar Basin were analysed. The results indicated that the Fudong slope showed the characteristics of low sediment input. Sediments mainly originated from the Shaqi uplift, and the sediment input gradually weakened from the early to the late J2t stages. The sedimentary system evolved from a delta to a meandering river, resulting in a delta front facies in the 1st member (J2t1) and a meandering river facies in the 2nd (J2t2) and 3rd (J2t3) members of the Toutunhe Formation. A sedimentary evolution pattern for the gentle slope with low sediment input was established. Thick deltaic sandbodies developed locally in the J2t1 stage. However, meandering rivers with high sinuosities predominantly developed and resulted in a striped geometry in the J2t2 and J2t3 members. Moreover, the meandering sandbodies exhibited an anastomosing morphology after multistage superposition. The channel and point bar facies in J2t2 were more developed than those in J2t3 because of sediment input differences. Under low-sediment input conditions, the sedimentary environment of the gentle slope belt in the lacustrine basin was controlled by changes in the palaeoclimate, palaeogeomorphology, gradient (slope) and base level. Palaeoclimate was the main factor controlling the evolution of the sedimentary environment. Palaeogeomorphology and slope controlled the distribution of sedimentary microfacies, channel sinuosity and sandbodies. Base-level change restricted the sandbody superimposition style. Under the low sediment input conditions of the Fudong slope, the subaqueous distributary channels of the delta environment and the point bars of the meandering river environment in the transitional belt of the Fudong slope are the main potential targets for stratigraphic petroleum reservoirs, whilst the 2nd member of the Toutunhe Formation (J2t2) is the main favourable interval for stratigraphic reservoir exploration.

Turbidite channel-levée transitions: insights from the Tachrift system (Complex 6, Taza-Guercif Basin, NE Morocco)

This contribution reports on the outcrop of one (Complex 6, hereafter) of multiple turbidite channel-levée complexes making the Tachrift system (Late Tortonian- early Messinian), beautifully exposed in NE Morocco as part of the clastic fill of the Taza-Guercif Basin. Geological mapping was integrated with facies analysis on 46 logs and physical stratigraphic correlations. Complex 6 consists of three sandstone-rich units labelled A, B, and C that progressively increase in grain-size and are laterally stacked in a SE-ward shifting fashion. Particularly, channel- fills and correlative levées of Units B and C have contrasting architectural styles which likely reflect changes in flow parameters (e.g., grain size, volume, density stratification etc.), channel sinuosity, and morphodynamics. Owing to magnificent 3D exposures, the ongoing study of Complex 6 outcrops will provide sedimentological characterization of channel-fills and correlative levée deposits, insights into evolution of their parent channel from inception trough abandonment, and sub-seismic lithological calibration of subsurface analogues.

Chronological evolution of Holocene floodplain of river Raidak within the Himalayan foreland basin, India

The present study aims to investigate the evolution of river networks and floodplain geomorphological features of river Raidak within the dynamic Himalayan foreland basin regime over 65 year's timescale (1955–2020). High resolution satellite images and old maps have been used to prepare the floodplain geomorphological maps. Additionally, field verification technique has been adopted to improve the accuracy of floodplain landforms mapping. Sedimentary log analysis was conducted in order to identify the floodplain types and fluvial architectural elements in the floodplain. The nature of channel oscillation has been assessed using different parameters (channel length, channel width, sinuosity, bank line migration and erosion-accretion area). Results showed that progressive migration of meander bends and channel shifting on a recent past time-scale have resulted into many floodplain geomorphic features such as cut-offs, palaeochannel, backswamps, abandoned channel and meander scroll bar on Holocene floodplain surface. These floodplain landforms are more prominent on the middle and lower part of the floodplain. Numerical investigation showed variation in channel sinuosity of the middle and lower reach of river Raidak-I (1.85, 1.64 and 1.73 during the year 1955, 1987 and 2020 respectively) suggesting channel lengthening and shortening during different time period through mender development and cut-offs formation. Result also shows spatiotemporal variation in channel width and increasing trend of erosion-accretion area during the period 1987–2020. The sedimentary log analysis suggests non-cohesive medium energy (specific stream power varies between 10 and 300 Wm-2) floodplain of principal class B characterized with meandering and braided channel pattern, multiple sequence of Holocene sediments and existence of different floodplain landforms. Different natural processes (variable discharge, frequent floods, active tectonics, meander migration and channel shifting) and human interferences (channelization, mining activities, construction of cross-sectional structures and land use changes) have been responsible for evolution and morphological modification of Raidak river system and their floodplains.

Evaluation of neotectonic activity using watershed geomorphic analysis: A case study in the west of Dokan Lake, Kurdistan Region, Iraq

The Iraqi Kurdistan Region's landscapes are the product of a complex merging of the effects of the collision between the Arabian and Eurasian plates and various geomorphic processes. A study of the Khrmallan drainage basin in the west of Dokan Lake, based on a morphotectonic study is a significant contribution to our understanding of the Neotectonic activity in the High Folded Zone. This study investigated an integrated method of detail morphotectonic mapping and geomorphic indices' analysis for determining the signal of Neotectonic activity, using the digital elevation model (DEM) and satellite images. The detailed morphotectonic map, along with extensive field data, revealed considerable variation in the relief and morphology of the study area, and eight morphotectonic zones were recognized. The presence of a high anomalous value in stream length gradient (SL) ranges from 19 to 769, increasing the channel sinuosity index (SI) reaching 1.5, and the tendency of basin shifting through the transverse topographic index (T) ranging from 0.02 to 0.5, conclude that the study area is tectonically active. The strong relationship between the growth of the Khalakan anticline and the activation of faulting is concurrent with the collision of the Arabian and Eurasian plates. A hypothesis of an antecedent can be applied to the Khrmallan valley.

Reconstructing paleosinuosity and sedimentary mass balance in the Upper Triassic Shinarump paleoriver in Utah and Arizona, U.S.A.

ABSTRACT The Upper Triassic Shinarump Member forms the basal part of the Chinle Formation in the western interior United States and was deposited by a continental-scale fluvial system which ran approximately 2,500 km from the Ouachita Orogen in the east into the Auld Lang Syne marine basin in the west. Previous studies of the Shinarump Member have concluded that the deposits represent a braided-river system but have not produced estimates for paleo-sinuosity and paleo-discharge. Recent advances in sedimentology allow detailed morphometric assessment of the nature of the river system that deposited the Shinarump Member enabling us to produce quantitative estimates for these parameters. We therefore present architectural data from the Shinarump Member in northern Arizona and Utah, supported by lithofacies data and 39 sandstone petrographic analyses, and a dataset of 4,298 paleocurrent measurements from trough cross-strata. Lithofacies and architectural analysis supports previous interpretations of the Shinarump and equivalent strata as braided-river deposits. Petrographic analysis shows that the Shinarump is dominated by monocrystalline quartz and exhibits low spatial variation in composition, ranging from 85.4% to 99.8% total quartz. Paleocurrent measurements are used to calculate the channel sinuosity of the fluvial system as varying between 1.02 and 1.77, with a median value of 1.33 (compared to the Yangtze River, ranging from 1.05 to 1.50 and the Ganges–Brahmaputra, ranging from 1.05 to 1.13 in their lower 250 km). Paleohydrological estimates using data from the architectural surveys produce slope estimates from 2.01 × 10–4 to 6.51 × 10–4 and bankfull discharge estimates from 4.36 × 103 m3 s–1 to 2.38 × 104 m3 s–1 for individual channels, comparable to extant continental-scale fluvial systems. Estimates of lifetime sediment transport volume range from 7.75 × 104 km3 to 6.09 × 105 km3, which are in order-of-magnitude agreement with estimates for the volume of the depositional sink (1.35 × 105 km3 to 4.17 × 105 km3). These results demonstrate the potential for paleohydrologic estimates to provide new avenues for analysis of heavily studied units.