Journal articles on the topic 'Fluvial bedforms'
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1
Seminara, Giovanni. "Effect of Grain Sorting on the Formation of Bedforms." Applied Mechanics Reviews 48, no. 9 (September 1, 1995): 549–63. http://dx.doi.org/10.1115/1.3023144.
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Grain sorting is a process observed in fluvial, coastal, and estuarian environments whereby the selective transport of different fractions of a sediment mixture gives rise to a non-uniform spatial distribution of the grain size probability density function. The formation of some fluvial bedforms (bedloadsheets and sand ridges) is shown to be generated or dominantly controlled by grain sorting. However, most bedforms (river dunes, free and forced fluvial bars, coastal ripples) are moderately affected by the sorting mechanism which is invariably found to lead to a damping effect on bedform growth. Recent investigations of the above phenomena are reviewed and new methodologic aspects arising in treating the instability of flow and bed topography in the presence of mixtures are pointed out.
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Wooldridge, C. L., and E. J. Hickin. "Step-pool and cascade morphology, Mosquito Creek, British Columbia: a test of four analytical techniques." Canadian Journal of Earth Sciences 39, no. 4 (April 1, 2002): 493–503. http://dx.doi.org/10.1139/e01-087.
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The identification and geometric definition of individual cascade and step-pool bedforms are investigated in a steep, coarse-grained, mountain stream, Mosquito Creek, by testing four analytical techniques: visual identification, zero-crossing, bedform differencing, and power spectral analysis. The test is the first use of these techniques in a headwater stream, and the analysis of two bed profiles showed that visual identification was able to (i) identify, (ii) determine the geometry of, and (iii) classify the type of individual bedforms better than the other methods. The other techniques were not able to differentiate step-pools from cascades, and the large range of grain sizes and bedform heights hampered their ability to consistently identify stepped bedforms. The step-pool (pronounced, channel-spanning steps that alternate with channel-spanning pools) and cascade (multi-tiered, partially channel-spanning structures) morphology in Mosquito Creek has formed in the last 20 years as fluvial action has restructured its previously engineered, revetment-lined, planar bed. The channel bed exhibits a morphologic regularity that power spectral analysis captured as periodic fluctuations in the bed profiles, with mean wavelengths slightly greater than those identified by the other methods. Further, the active reorganization of revetment has formed stepped structures with geometries similar (i.e., height to wavelength ratios) to stepped features found in natural mountain streams. Channel slope partially controlled bedform geometry (wavelength and height), and bedform height weakly controlled individual step spacing, but there was no relation between wavelength and grain size (D90).
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Tinkler, K. J. "Fluvially sculpted rock bedforms in Twenty Mile Creek, Niagara Peninsula, Ontario." Canadian Journal of Earth Sciences 30, no. 5 (May 1, 1993): 945–53. http://dx.doi.org/10.1139/e93-079.
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Sculpted rock bedforms (s-forms) on Whirlpool Sandstone are described from the bed of Twenty Mile Creek. The morphologies identified (undulating surfaces, rises, furrows, comma forms, spindles, potholes, and transverse troughs) are those described for sculpted bedrock forms (p-forms, s-forms) developed in subglacial environments. Additional morphologies identified are undercut downsteps and quarried surfaces in the lee of bedrock rises. Morphological differences between the subglacial and fluvial forms are attributed to the difference between confined conduit flow in the subglacial case and open-channel flow in the fluvial examples. In fluvial systems the descending bedrock surface presents rock differently to oncoming flows and favours certain s-forms (quarried lee faces and undulating surfaces). In a strong-flow fluvial environment s-forms develop by wear. Dominant sediment-transport modes are large clasts (up to metre dimensions) and suspended silt–clay with a small (< 7%) hard or heavy-mineral component. Hydraulic quarrying, which removes fracture-delimited blocks from the bed, interrupts the process. Although fluvial s-forms are similar to subglacial s-forms, large stable vortices may not exist in the fluvial context over the range of effective stages. Upper regime flow is common over bedrock reaches, and flow acceleration at small downsteps (knickpoints) magnifies the duration and spatial extent of wear effective velocities.
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Nones, Michael. "Special Issue “Laboratory Geosciences: Modelling Surface Processes” in Geosciences." Geosciences 8, no. 11 (October 25, 2018): 386. http://dx.doi.org/10.3390/geosciences8110386.
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In the last decades, new and advanced measurement techniques have been developed to track the dynamics of surface processes and the formation of river bedforms, bars and island as well as complex fluvial networks, gullies and rills by means of small-scale laboratory experiments, aiming to integrate and support mathematical models [...]
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Zomer, Judith Y., Suleyman Naqshband, and Antonius J. F. Hoitink. "Short communication: A tool for determining multiscale bedform characteristics from bed elevation data." Earth Surface Dynamics 10, no. 5 (September 6, 2022): 865–74. http://dx.doi.org/10.5194/esurf-10-865-2022.
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Abstract. Systematic identification and characterization of bedforms from bathymetric data are crucial in many studies of fluvial processes. Automated and accurate processing of bed elevation data is challenging where dune fields are complex or irregular and (especially) where multiple scales co-exist. Here, we introduce a new tool to quantify dune properties from bathymetric data representing large primary and smaller superimposed secondary dunes. A first step in the procedure is to decompose the bathymetric data using a LOESS algorithm. Steep lee-side slopes of primary dunes are preserved by implementing objective breaks in the algorithm, accounting for discontinuities in the bed elevation profiles at the toe of the lee-side slope. The steep lee slopes are then approximated by fitting a sigmoid function. Following the decomposition of the bathymetric data, bedforms are identified based on a zero crossing, and morphological properties are calculated. The approach to bedform decomposition presented herein is particularly applicable where secondary dunes are large and filtering using conventional continuously differentiable functions could thus easily lead to undesired smoothing of the primary morphology. Application of the tool to two bathymetric maps demonstrates that it successfully decomposes bathymetric data, identifies primary and secondary dunes, and preserves steeper lee-side slopes of primary dunes.
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Fowler, A. C., and M. Chapwanya. "An instability theory for the formation of ribbed moraine, drumlins and mega-scale glacial lineations." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 470, no. 2171 (November 8, 2014): 20140185. http://dx.doi.org/10.1098/rspa.2014.0185.
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We present a theory for the coupled flow of ice, subglacial water and subglacial sediment, which is designed to represent the processes which occur at the bed of an ice sheet. The ice is assumed to flow as a Newtonian viscous fluid, the water can flow between the till and the ice as a thin film, which may thicken to form streams or cavities, and the till is assumed to be transported, either through shearing by the ice, squeezing by pressure gradients in the till, or by fluvial sediment transport processes in streams or cavities. In previous studies, it was shown that the dependence of ice sliding velocity on effective pressure provided a mechanism for the generation of bedforms resembling ribbed moraine, while the dependence of fluvial sediment transport on water film depth provides a mechanism for the generation of bedforms resembling mega-scale glacial lineations. Here, we combine these two processes in a single model, and show that, depending largely on the granulometry of the till, instability can occur in a range of types which range from ribbed moraine through three-dimensional drumlins to mega-scale glacial lineations.
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Fathan Al-Hakim, Abdul Fauzan, and Yan Rizal. "Fasies Sedimentasi dan Elemen Arsitektur Formasi Citalang di Desa Sidamukti, Majalengka, Provinsi Jawa Barat." Jurnal Geologi dan Sumberdaya Mineral 22, no. 3 (October 5, 2021): 177. http://dx.doi.org/10.33332/jgsm.geologi.v22i3.643.
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Daerah Majalengka merupakan satu daerah di Jawa Barat yang sangat menarik untuk dilakukan kajian geologi baik yang berkaitan dengan sedimentologi, tektonik maupun paleontologi. Salah satu objek yang menarik untuk dikaji ulang adalah Formasi Citalang, dimana uraian tentang formasi ini masih banyak terdapat perbedaan tentang satuan batuan penyusunnya, umur dan lingkungan pengendapannya. Disini kajian tentang formasi Citalang ditinjau dari sedimentologinya.Formasi Citalang di daerah penelitian Desa Sidamukti, Kabupaten Majalengka, Provinsi Jawa Barat tersusun atas 6 satuan batuan, yaitu: perselingan batupasir dan konglomerat sisipan tuf, perselingan batupasir dan batulempung, perselingan batupasir dan konglomerat, batupasir sisipan batulanau, perselingan batupasir dan konglomerat dengan sisipan batulanau, serta perselingan batupasir dan batulanau. Dari pengukuran penampang stratigrafi lintasan terpilih didapatkan 10 litofasies yang secara keseluruhan dijumpai dalam masing-masing satuan batuan, berupa: Fine Mud (Fm), Fine Silt Mud (Fsm), Massive Sandstone (Sm), Horizontal Sandstone (Sh), Low Angle Cross Lamination Sandstone (Sl), Ripple Cross Lamination Sandstone (Sr), Trough Cross Bed Sandstone (St), Gravel Matrix Supported Graded Bedding (Gmg), Gravel Clast Supported Graded Bedding (Gcg), Gravel Clast Supported Massive (Gcm). Elemen arsitektural yang terbentuk pada sistem pengendapan Formasi Citalang adalah Gravel Bar and Bedforms (GB), Sandy Bedform (SB), dan Sediment Gravity Flow (SG), yang diinterpretasikan terjadi pada lingkungan pengendapan fluvial berupa sungai teranyam.Katakunci: Formasi Citalang, elemen arsitektur, fluvial, litofasies, sungai teranyam.
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Wilson, Andrew, Niels Hovius, and Jens M. Turowski. "Upstream-facing convex surfaces: Bedrock bedforms produced by fluvial bedload abrasion." Geomorphology 180-181 (January 2013): 187–204. http://dx.doi.org/10.1016/j.geomorph.2012.10.010.
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Musa, Mirko, Craig Hill, Fotis Sotiropoulos, and Michele Guala. "Performance and resilience of hydrokinetic turbine arrays under large migrating fluvial bedforms." Nature Energy 3, no. 10 (July 30, 2018): 839–46. http://dx.doi.org/10.1038/s41560-018-0218-9.
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Yan, Ge, Heqin Cheng, Lizhi Teng, Wei Xu, Yuehua Jiang, Guoqiang Yang, and Quanping Zhou. "Analysis of the Use of Geomorphic Elements Mapping to Characterize Subaqueous Bedforms Using Multibeam Bathymetric Data in River System." Applied Sciences 10, no. 21 (October 30, 2020): 7692. http://dx.doi.org/10.3390/app10217692.
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Riverbed micro-topographical features, such as crest and trough, flat bed, and scour pit, indicate the evolution of fluvial geomorphology, and have an influence on the stability of underwater structures and overall scour pits. Previous studies on bedform feature extraction have focused mainly on the rhythmic bed surface morphology and have extracted crest and trough, while flat bed and scour pit have been ignored. In this study, to extend the feature description of riverbeds, geomorphic elements mapping was used by employing three geomorphic element classification methods: Wood’s criteria, a self-organization map (SOM) technique, and geomorphons. The results showed that geomorphic element mapping can be controlled by adjusting the slope tolerance and curvature tolerance of Wood’s criteria, using the map unit number and combination of the SOM technique and the flatness of geomorphons. Relatively flat bed can be presented using “plane”, “flat planar”, and “flat” elements, while scour pit can be presented using a “pit” element. A comparison of the difference between parameter settings for landforms and bedforms showed that SOM using 8 or 10 map units is applicable for land and underwater surface and is thus preferentially recommended for use. Furthermore, the use of geomorphons is recommended as the optimal method for characterizing bedform features because it provides a simple element map in the absence of area loss.
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Maciaszek, Piotr, Lilianna Chomiak, Robert Wachocki, and Marek Widera. "The interpretative significance of ripple-derived sedimentary structures within an upper Neogene fluvial succession of central Poland." Geologos 25, no. 1 (April 1, 2019): 1–13. http://dx.doi.org/10.2478/logos-2019-0001.
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Abstract Sedimentary structures discussed in the present study are genetically linked to ripples that consist of pure sand or alternating sand and mud layers. All types of ripple-related structures, such as climbing-ripple cross-lamination and heterolithic bedding, i.e., flaser, wavy and lenticular (nodular), have been identified for the first time in fluvial strata that have been characterised previously as commonly massive. These small-scale bedforms, produced by migrating ripples, have been documented in a fluvial channel of late Neogene age in central Poland. The abundance and co-occurrence of the structures discussed and their spatial distribution provide evidence of their formation under very low-energy conditions, when flow velocity changed markedly, but was often significantly less than 0.5 m/s. Therefore, these ripple-derived sedimentary structures are here recognised as typical of channel fills of an anastomosing river.
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Noll, C. A., and M. Hall. "FLUVIAL ARCHITECTURE AND THE TECTONIC CONTROL ON DEPOSITION OF ONSHORE EUMERALLA FORMATION, OTWAY RANGES, VICTORIA: IMPLICATIONS FOR EXPLORATION IN THE EARLY CRETACEOUS OTWAY BASIN." APPEA Journal 43, no. 1 (2003): 99. http://dx.doi.org/10.1071/aj02005.
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Spectacular outcrops of the terrestrial Aptian-Albian Eumeralla Formation are exposed in the Skenes Creek– Wongarra region, located on the eastern margin of the Otway Ranges, Victoria. The succession comprises mudstone-dominated floodplain and lacustrine successions and fluvially-derived sandstones. Lithofacies observed in the study area comprise intraformational and exotically derived conglomerate, massive and planar laminated sandstone, trough and tabular cross-bedded sandstone, ripple laminated sandstone, interbedded sandstone and mudstone, massive to laminated mudstone and thin coal seams. Architectural analysis of the fluvial system reveals these lithofacies are arranged into architectural elements that include channel elements, sandy bedforms, downstream and lateral accretion elements, laminated sand sheets and overbank fines elements.The fluvial system is characterised by low-sinuousity, braided river channels with high width to depth ratios. Palaeocurrent data indicates that the generally westward palaeoflow is interpreted to have been diverted into local axial-through drainage patterns by active northeast trending normal faults. One of these, the Skenes Creek Fault, is also likely to have structurally isolated floodplain and lacustrine successions from the main channel belt, leading to the deposition of an anomalously thick coal measure sequence in the hanging wall of the fault. The local study therefore provides insight into regional lithofacies and potential source rock distributions, and the associated tectonostratigraphic evolution of the Eumeralla Formation in the eastern Otway Basin. While the nature of the Eumeralla Formation sandstone does not lend itself to good reservoir properties, the geometry and internal structure of the sands provide an excellent model for other fluvial sandstone reservoir reconstructions.
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Guerit, Laure, Xiao-Ping Yuan, Sébastien Carretier, Stéphane Bonnet, Sébastien Rohais, Jean Braun, and Delphine Rouby. "Fluvial landscape evolution controlled by the sediment deposition coefficient: Estimation from experimental and natural landscapes." Geology 47, no. 9 (July 10, 2019): 853–56. http://dx.doi.org/10.1130/g46356.1.
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Abstract The evolution of a fluvial landscape is a balance between tectonic uplift, fluvial erosion, and sediment deposition. The erosion term can be expressed according to the stream power model, stating that fluvial incision is proportional to powers of river slope and discharge. The deposition term can be expressed as proportional to the sediment flux divided by a transport length. This length can be defined as the water flux times a scaling factor ζ. This factor exerts a major control on the river dynamics, on the spacing between sedimentary bedforms, or on the overall landscape erosional behavior. Yet, this factor is difficult to measure either in the lab or in the field. Here, we propose a new formulation for the deposition term based on a dimensionless coefficient, G, which can be estimated at the scale of a landscape from the slopes of rivers at the transition between a catchment and its fan. We estimate this deposition coefficient from 29 experimental catchment–alluvial fan systems and 68 natural examples. Based on our data set, we support the idea of Davy and Lague (2009) that G is a relevant parameter to characterize the erosional and transport mode of a fluvial landscape, which can be field calibrated, with a continuum from detachment-limited (G = 0) to transport-limited behavior (G >0.4 from the studied examples).
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Daryono, Sapto Kis, Carolus Prasetyadi, Eko Teguh Paripurno, Sutanto Sutanto, and Aditya Zaenalfi Faozi. "Facies and architectural analysis of Paleogen fluvial deposits of the measured section of Rambangnia and Air Napalan Rivers in Palembang Sub-basin." Journal of Earth and Marine Technology (JEMT) 3, no. 1 (October 12, 2022): 24–33. http://dx.doi.org/10.31284/j.jemt.2022.v3i1.3606.
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Paleogene fluvial deposits have an important problem as pre-rift deposits, which occur before or at the same time as the formation of the basin. The research results on facies analysis and interpretation of the depositional environment of Paleogene deposits located in the Garba Hills will later explain and describe the history of the formation and stratigraphic evolution of sedimentary rocks in the South Sumatra Basin, reflected in the lithological and facies characteristics. The facies analysis was carried out on a stratigraphic cross-section with a thickness of ± 107.37 meters and ± 11.06 meters on the measurement path of the Rambangnia River and Air Napalan River, which are located in the Ogan Komering Ulu area, South Sumatra. Seven lithofacies developed on two measured paths are matrix supported gradded gravel (Gmg), gravel matrix supported Massive (Gmm), through cross-bedded (St), massive sandstone (Sm), horizontally bedded sandstones (Sh), parallel laminated siltstone and claystone (F1), massive siltstones and mudstones (Fsm). Asosiasi fasies didapatkan berupa Sedimentary Gravity Flow (SG), Gravel Bars (GB), Sandy Bedforms (SB), channel (CH), Overbank fine (FF). The interpretation of the depositional environment shows a fluvial environment, the type of braided river with a gravel braided rivers model with sedimentary gravity flows.Paleogene fluvial deposits have an important problem as pre-rift deposits, which occur before or at the same time as the formation of the basin. The research results on facies analysis and interpretation of the depositional environment of Paleogene deposits located in the Garba Hills will later explain and describe the history of the formation and stratigraphic evolution of sedimentary rocks in the South Sumatra Basin, reflected in the lithological and facies characteristics. The facies analysis was carried out on a stratigraphic cross-section with a thickness of ± 107.37 meters and ± 11.06 meters on the measurement path of the Rambangnia River and Air Napalan River, which are located in the Ogan Komering Ulu area, South Sumatra. Seven lithofacies developed on two measured paths are matrix supported gradded gravel (Gmg), gravel matrix supported Massive (Gmm), through cross-bedded (St), massive sandstone (Sm), horizontally bedded sandstones (Sh), parallel laminated siltstone and claystone (F1), massive siltstones and mudstones (Fsm). Asosiasi fasies didapatkan berupa Sedimentary Gravity Flow (SG), Gravel Bars (GB), Sandy Bedforms (SB), channel (CH), Overbank fine (FF). The interpretation of the depositional environment shows a fluvial environment, the type of braided river with a gravel braided rivers model with sedimentary gravity flows.
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Shan, Xin, Xuefa Shi, Peter D. Clift, Ashraf Ali Seddique, Shengfa Liu, Chengpeng Tan, Jianguo Liu, Rased Hasan, Jingrui Li, and Zhaojun Song. "Sedimentology of the modern seasonal lower Ganges River with low inter-annual peak discharge variance, Bangladesh." Journal of the Geological Society 178, no. 1 (October 9, 2020): jgs2020–094. http://dx.doi.org/10.1144/jgs2020-094.
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The Ganges River, one of the largest rivers on Earth, is a typical monsoonal and flood-controlled system but has low inter-annual peak discharge variability. The seasonal discharge can reach 70 000 m3 s−1 during the wet season but maintains a low base flow of 500–3000 m3 s−1 during the dry season. However, the constancy in peak discharge every year categorizes the lower Ganges River as a river with low inter-annual peak discharge variability. This paper examines the modern lower Ganges River by conducting a detailed process-oriented investigation of the main channel, channel margin and overbank deposits, supplemented by satellite image observation and comparison with other modern fluvial systems. The channel and braid bar deposits show a dominance of small-scale to medium-scale cross-sets, with a variety of accretion processes constructing braid bars. The braid bar and channel deposits are typical of facies models of rivers with low inter-annual peak discharge variance. In contrast, the channel flank deposits are dominated by planar lamination, massive sand and mud couplets, and some ripple cross-lamination, with very little cross-bedding. Characteristic channel margin deposits represent sediments that accumulated by high-speed flows, multiple-surge and rapidly depositing flows, rapid or regular waning flows and hyperconcentrated flows. The overbank deposits predominantly comprise current ripples with long, thin bedforms and soft sediment deformation structures, which record flow transformation on the muddy flat topography and the processes of an unstable river bank. Our study shows that the channel margin and floodplain deposits are entirely different from those of the braid bar and channel. The bedform distribution of the fluvial deposits here (main channel, channel margin and overbank) may be an important tool in the identification of similar seasonal rivers with low inter-annual peak discharge variance and in the interpretation of fluvial processes.Supplementary material: The sediment texture and the depositional age is available at: https://doi.org/10.6084/m9.figshare.c.5144403
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Moskalewicz, Damian, Robert J. Sokołowski, and Stanisław Fedorowicz. "River response to climate and sea level changes during the Late Saalian/Early Eemian in northern Poland – a case study of meandering river deposits in the Chłapowo cliff section." Geologos 22, no. 1 (March 1, 2016): 1–14. http://dx.doi.org/10.1515/logos-2016-0001.
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Abstract Fluvial sediments in the Chłapowo cliff section were studied in order to reconstruct their palaeoflow conditions and stratigraphical position. Lithofacies, textural and palaeohydraulic analyses as well as luminescence dating were performed so as to achieve the aim of study. Sedimentary successions were identified as a record of point bar cycles. The fluvial environment probably functioned during the latest Saalian, shortly after the retreat of the Scandinavian Ice Sheet. Discharge outflow was directed to the northwest. The river used the older fluvioglacial valley and probably was directly connected to the Eem Sea. Good preservation and strong aggradation of point-bar cycles were related to a rapid relative base level rise. The meandering river sediments recognised showed responses to climate and sea level changes as illustrated by stratigraphical, morphological and sedimentological features of the strata described. The present study also revealed several insights into proper interpretation of meandering fluvial successions, in which the most important were: specific lithofacies assemblage of GSt (St, Sp) → Sl → SFrc → Fm (SFr) and related architectural elements: channel/sandy bedforms CH/SB → lateral accretion deposits LA → floodplain fines with crevasse splays FF (CS); upward-fining grain size and decreasing content of denser heavy minerals; estimated low-energy flow regime with a mean depth of 1.6–3.3 m, a Froude number of 0.2–0.4 and a sinuosity of 1.5.
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Fambrini, Gelson Luís, Virgínio Henrique M. L. Neumann, José Acioli B. Menezes-Filho, Wellington F. Da Silva-Filho, and Édison Vicente De Oliveira. "Facies architecture of the fluvial Missão Velha Formation (Late Jurassic–Early Cretaceous), Araripe Basin, Northeast Brazil: paleogeographic and tectonic implications." Acta Geologica Polonica 67, no. 4 (December 1, 2017): 515–45. http://dx.doi.org/10.1515/agp-2017-0029.
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Abstract Sedimentological analysis of the Missão Velha Formation (Araripe Basin, northeast Brazil) is the aim of this paper through detailed facies analysis, architectural elements, depositional systems and paleocurrent data. The main facies recognized were: (i) coarse-grained conglomeratic sandstones, locally pebbly conglomerates, with abundant silicified fossil trunks and several large-to-medium trough cross-stratifications and predominantly lenticular geometry; (ii) lenticular coarse-to-medium sandstones with some granules, abundant silicified fossil wood, and large-to-medium trough cross-stratifications, cut-and fill features and mud drapes on the foresets of cross-strata, (iii) poorly sorted medium-grained sandstones with sparse pebbles and with horizontal stratification, (iv) fine to very fine silty sandstones, laminated, interlayered with (v) decimetric muddy layers with horizontal lamination and climbing-ripple cross-lamination. Nine architectural elements were recognized: CH: Channels, GB: Gravel bars and bed forms, SB: Sand bars and bedforms, SB (p): sand bedform with planar cross-stratification, OF: Overbank flow, DA: Downstream-accretion macroforms, LS: Laminated sandsheet, LA: Lateral-accretion macroforms and FF: Floodplain fines. The lithofacies types and facies associations were interpreted as having been generated by alluvial systems characterized by (i) high energy perennial braided river systems and (ii) ephemeral river systems. Aeolian sand dunes and sand sheets generated by the reworking of braided alluvial deposits can also occur. The paleocurrent measurements show a main dispersion pattern to S, SE and SW, and another to NE/E. These features imply a paleodrainage flowing into the basins of the Recôncavo-Tucano-Jatobá.
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Praeg, Dan, Bruno d’Anglejan, and James P. M. Syvitski. "Seismostratigraphy of the Middle St. Lawrence Esturary: A Late Quaternary Glacial Marine to Estuarine Depositional/Erosional Record." Géographie physique et Quaternaire 46, no. 2 (November 28, 2007): 133–50. http://dx.doi.org/10.7202/032899ar.
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ABSTRACTA buried bedrock trough 350 m deep extends 100 km above Saguenay Fjord beneath the North Channel of the middle estuary. Four of five regional seismostratigraphic units are recognized in and adjacent to the trough; unit 1 (glacial ice-contact) and older sediments might also be present beneath the largely unpenetrated trough axis. Units 2 and 3 represent thick glacial marine sediments deposited in the >550 m deep waters of the Goldthwait Sea after glacial withdrawal ca. 13 ka BP: lower draped muds 10-20 m thick (unit 2) suggest deposition proximal to a retreating ice margin, while upper onlapping muds > 290 m thick (unit 3) record distal basin-filling; lateral transition to a coarse-grained proximal wedge 5*260 m thick (unit 2) is indicated by unit 3 reflectors rising and strengthening towards the Saguenay entrance, where a stable ice-margin ca. 13-11 ka BP supplied sediment to the lower and middle estuary. Unit 4 corresponds to lobes over 30 m thick on both sides of the upper North Channel, recording marginal input from glacial fluvio-deltaic sources. Unit 5 (estuarine sands, gravels and muds =£30 m thick) unconformably overlies glacial units. A smooth unconformity surface records erosion (at least 15 m, to axial depths >150m) by strong currents; irregular relief above depths of 25-50 m might relate to relative sea levels below present ca. 7-6 ka BP. Sand bedforms (apparently inactive) occur at the estuary floor, and possibly buried beneath estuarine muds; buried bedforms would imply an early Holocene genesis. Greatest thicknesses of estuarine mud coincide with adjacent fluvial discharges. Sandy/gravelly veneers form the estuary floor in most places. Mass displacement has disturbed units 3 and 5 along the northern, and locally southern, walls of the North Channel.
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MARTINIUS, ALLARD W., and STUART GOWLAND. "Tide-influenced fluvial bedforms and tidal bore deposits (Late Jurassic Lourinhã Formation, Lusitanian Basin, Western Portugal)." Sedimentology 58, no. 1 (September 23, 2010): 285–324. http://dx.doi.org/10.1111/j.1365-3091.2010.01185.x.
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Yepez, Santiago Paul, Alain Laraque, Carlo Gualtieri, Frédéric Christophoul, Claudio Marchan, Bartolo Castellanos, Jose Manuel Azocar, Jose Luis Lopez, and Juan Alfonso. "Morphodynamic change analysis of bedforms in the Lower Orinoco River, Venezuela." Proceedings of the International Association of Hydrological Sciences 377 (April 16, 2018): 41–50. http://dx.doi.org/10.5194/piahs-377-41-2018.
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Abstract. The Orinoco River has the third largest discharge in the world, with an annual mean flow of 37 600 m3 s−1 at its outlet to the Atlantic Ocean. Due to the presence of the Guiana Shield on the right bank, the lower reach of the Orinoco has a plan form characterized by contraction and expansion zones. Typical 1–1.5 km wide narrow reaches are followed by 7–8 km wide reaches. A complex pattern of bed aggradation and degradation processes takes place during the annual hydrological regime. A series of Acoustic Doppler Current Profiler (ADCP) transects were collected on an expansion channel in the Orinoco River, specifically over a fluvial island, representative of the lower Orinoco. In this study, temporal series of bathymetric cartography obtained by ADCP profiles combined with Differential Global Position System (DGPS) measurements (with dual-frequency), were used to recover the local displacement of bed forms in this island. The principal aims of this analysis were: (1) to understand the dynamics and evolution of sand waves and bars at this section and (2) to quantify the volume (erosion vs. accretion) of a mid-channel bar with dunes by applying DEM of Difference (DoD) maps on time series of bathymetric data. This required sampling with ADCP transects during the months of: May 2016; November 2016 and April 2017. Each bathymetric transect was measured twice, 1 day apart and on the same trajectory obtained by a GPS receptor. The spatial analysis of these ADCP transects is presented as a novel tool in the acquisition of time series of bathymetry for a relatively deep section (∼20 m) and under variable flow conditions.
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Adams, David L., and Andrea Zampiron. "Short communication: Multiscalar roughness length decomposition in fluvial systems using a transform-roughness correlation (TRC) approach." Earth Surface Dynamics 8, no. 4 (December 9, 2020): 1039–51. http://dx.doi.org/10.5194/esurf-8-1039-2020.
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Abstract. In natural open-channel flows over complex surfaces, a wide range of superimposed roughness elements may contribute to flow resistance. Gravel-bed rivers present a particularly interesting example of this kind of multiscalar flow resistance problem, as both individual grains and bedforms may contribute to the roughness length. In this paper, we propose a novel method of estimating the relative contribution of different physical scales of in-channel topography to the total roughness length, using a transform-roughness correlation (TRC) approach. The technique, which uses a longitudinal profile, consists of (1) a wavelet transform which decomposes the surface into roughness elements occurring at different wavelengths and (2) a “roughness correlation” that estimates the roughness length (ks) associated with each wavelength based on its geometry alone. When applied to original and published laboratory experiments with a range of channel morphologies, the roughness correlation estimates the total ks to approximately a factor of 2 of measured values but may perform poorly in very steep channels with low relative submergence. The TRC approach provides novel and detailed information regarding the interaction between surface topography and fluid dynamics that may contribute to advances in hydraulics, bedload transport, and channel morphodynamics.
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Pannone, Marilena, and Annamaria De Vincenzo. "Theoretical Investigation of Equilibrium Dynamics in Braided Gravel Beds for the Preservation of a Sustainable Fluvial Environment." Sustainability 13, no. 3 (January 25, 2021): 1246. http://dx.doi.org/10.3390/su13031246.
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Gravel bars have an important role in the exchange between surface and subsurface waters, in preventing and mitigating riverbank erosion, in allowing the recreational use of rivers, and in preserving fluvial or riparian habitats for species of fishes, invertebrates, plants, and birds. In many cases, gravel bars constitute an important substrate for the establishment and development of ground flora and woody vegetation and guarantee higher plant diversity. A sustainable management of braided rivers should, therefore, ensure their ecological potential and biodiversity by preserving a suitable braiding structure over time. In the present study, we propose an analytical–numerical model for predicting the evolution of gravel bars in conditions of dynamical equilibrium. The model is based on the combination of sediment balance equation and a regression formula relating dimensionless unit bedload rate and stream power. The results highlight the dependence of the evolving sediment particles’ pattern on the ratio of initial macro-bedforms longitudinal dimension to river width, which determines the gradual transition from advective and highly braiding to diffusive transport regime. Specifically, the tendency to maintain braiding and flow bifurcation is associated with equilibrium average bed profiles and, therefore, equilibrium average stream power characterized by the maximum period that does not exceed transverse channel dimension.
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Bramante, James F., J. Taylor Perron, Andrew D. Ashton, and Jeffrey P. Donnelly. "Experimental quantification of bedrock abrasion under oscillatory flow." Geology 48, no. 6 (March 18, 2020): 541–45. http://dx.doi.org/10.1130/g47089.1.
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Abstract Although wave-driven abrasion of submarine bedrock affects the evolution of rocky coasts and reefs globally, the dependence of the abrasion rate on wave forcing and sediment availability remains poorly quantified. We performed experiments in which an artificial substrate was abraded by varying amounts of coarse-grained sediment subjected to oscillatory flows. In these experiments, the bedrock incision rate scaled by the square of bedrock tensile strength (I, m yr–1 MPa2) varied with mean root-mean-square (rms) velocity (<urms>, m s–1) according to a power law, I = 1.0<urms>4.2 (angle brackets indicate time-averaging over an entire experiment). Additionally, the relationship between sediment load and bedrock incision rate demonstrates tools and cover effects similar to abrasion in fluvial environments, such that incision is fastest at intermediate sediment loads. However, because oscillatory flows accumulate sediment into bedforms, the increased bedrock exposure reduces the efficiency of the cover effect for high sediment loads relative to unidirectional flow. Our results provide an empirical model that can be used to predict bedrock incision rates in nearshore environments based on wave forcing.
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ROE, SIGNE-LINE. "Cross-strata and bedforms of probable transitional dune to upper-stage plane-bed origin from a Late Precambrian fluvial sandstone, northern Norway." Sedimentology 34, no. 1 (February 1987): 89–101. http://dx.doi.org/10.1111/j.1365-3091.1987.tb00562.x.
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Cheviron, B., and R. Moussa. "Determinants of modelling choices for 1-D free-surface flow and erosion issues in hydrology: a review." Hydrology and Earth System Sciences Discussions 12, no. 9 (September 8, 2015): 9091–155. http://dx.doi.org/10.5194/hessd-12-9091-2015.
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Abstract. This review paper investigates the determinants of modelling choices, for numerous applications of 1-D free-surface flow and erosion equations, across multiple spatiotemporal scales. We aim to characterize each case study by its signature composed of model refinement (Navier-Stokes: NS, Reynolds-Averaged Navier-Stokes: RANS, Saint-Venant: SV or Approximations of Saint-Venant: ASV), spatiotemporal scales (domain length: L from 1 cm to 1000 km; temporal scale: T from 1 second to 1 year; flow depth: H from 1 mm to 10 m), flow typology (Overland: O, High gradient: Hg, Bedforms: B, Fluvial: F) and dimensionless numbers (Dimensionless time period T*, Reynolds number Re, Froude number Fr, Slope S, Inundation ratio Λz, Shields number θ). The determinants of modelling choices are therefore sought in the interplay between flow characteristics, cross-scale and scale-independent views. The influence of spatiotemporal scales on modelling choices is first quantified through the expected correlation between increasing scales and decreasing model refinements, identifying then flow typology a secondary but mattering determinant in the choice of model refinement. This finding is confirmed by the discriminating values of several dimensionless numbers, that prove preferential associations between model refinements and flow typologies. This review is intended to help each modeller positioning his (her) choices with respect to the most frequent practices, within a generic, normative procedure possibly enriched by the community for a larger, comprehensive and updated image of modelling strategies.
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Cheviron, Bruno, and Roger Moussa. "Determinants of modelling choices for 1-D free-surface flow and morphodynamics in hydrology and hydraulics: a review." Hydrology and Earth System Sciences 20, no. 9 (September 14, 2016): 3799–830. http://dx.doi.org/10.5194/hess-20-3799-2016.
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Abstract. This review paper investigates the determinants of modelling choices, for numerous applications of 1-D free-surface flow and morphodynamic equations in hydrology and hydraulics, across multiple spatiotemporal scales. We aim to characterize each case study by its signature composed of model refinement (Navier–Stokes: NS; Reynolds-averaged Navier–Stokes: RANS; Saint-Venant: SV; or approximations to Saint-Venant: ASV), spatiotemporal scales and subscales (domain length: L from 1 cm to 1000 km; temporal scale: T from 1 s to 1 year; flow depth: H from 1 mm to 10 m; spatial step for modelling: δL; temporal step: δT), flow typology (Overland: O; High gradient: Hg; Bedforms: B; Fluvial: F), and dimensionless numbers (dimensionless time period T*, Reynolds number Re, Froude number Fr, slope S, inundation ratio Λz, Shields number θ). The determinants of modelling choices are therefore sought in the interplay between flow characteristics and cross-scale and scale-independent views. The influence of spatiotemporal scales on modelling choices is first quantified through the expected correlation between increasing scales and decreasing model refinements (though modelling objectives also show through the chosen spatial and temporal subscales). Then flow typology appears a secondary but important determinant in the choice of model refinement. This finding is confirmed by the discriminating values of several dimensionless numbers, which prove preferential associations between model refinements and flow typologies. This review is intended to help modellers in positioning their choices with respect to the most frequent practices, within a generic, normative procedure possibly enriched by the community for a larger, comprehensive and updated image of modelling strategies.
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Dix, George R., and Marianne P. Molgat. "Character of the Middle Ordovician Sauk-Tippecanoe sequence boundary in the Ottawa Embayment (eastern Ontario): possible evidence for platform-interior, Taconic tectonism." Canadian Journal of Earth Sciences 35, no. 6 (June 1, 1998): 603–19. http://dx.doi.org/10.1139/e98-017.
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In eastern Ontario, a Middle Ordovician disconformity that separates predominantly sandstone of the Rockcliffe Formation from underlying dolomite of the Carillon Formation (Beekmantown Group) has, historically, been considered equivalent to the Sauk-Tippecanoe sequence boundary. The character of the formation contact varies considerably, and includes (1) rare, serrated micropinnacles (centimetres in height); (2) smoothed, irregular to undulose erosional bedforms along shallow (<30 cm) incised channels at least ten's of metres in width; (3) a planar boundary with no obvious evidence of erosion; (4) compaction effects across the boundary, as well as within uppermost Carillon and lowermost Rockcliffe strata; and (5) interbedding of Carillon- and Rockcliffe-like lithologies. The latter two observations suggest that, locally, the disconformity represents a relatively minor gap in time. Local, irregular paleotopography is interpreted as some combination of paleokarst, mechanical erosion, and differential sediment loading. The Carillon-to-Rockcliffe transition, from peritidal carbonates to marine or estuarine sandstones, is punctuated by local, anomalous structural and stratigraphic features: ptygmmatically folded fractures, local disconformities, and deposition, then differential erosion of high-energy fluvial-dominated sediments. Differential erosion, fracturing, and paleokarst are local, anomalous attributes of the pre-Carillon paleosurface as well. Combined, these events bracket Carillon deposition, and are interpreted to reflect local platform-interior tectonism coincident with onset of distal Taconic orogenesis. Platform-interior expression of distant, developing changes in plate-boundary dynamics may be linked to incipient basement reactivation along an underlying, shallowly buried Proterozoic fault system, later manifest as the Ottawa-Bonnechere Graben.
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Dalla Barba, Federico, and Francesco Picano. "Direct numerical simulation of the scouring of a brittle streambed in a turbulent channel flow." Acta Mechanica 232, no. 12 (October 13, 2021): 4705–28. http://dx.doi.org/10.1007/s00707-021-03075-5.
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AbstractThe natural processes involved in the scouring of submerged sediments are crucially relevant in geomorphology along with environmental, fluvial, and oceanographic engineering. Despite their relevance, the phenomena involved are far from being completely understood, in particular for what concerns cohesive or stony substrates with brittle bulk mechanical properties. In this frame, we address the investigation of the mechanisms that govern the scouring and pattern formation on an initially flattened bed of homogenous and brittle material in a turbulent channel flow, employing direct numerical simulation. The problem is numerically tackled in the frame of peridynamic theory, which has intrinsic capabilities of reliably reproducing crack formation, coupled with the Navier–Stokes equations by the immersed boundary method. The numerical approach is reported in detail here and in the references, where extensive and fully coupled benchmarks are provided. The present paper focuses on the role of turbulence in promoting the brittle fragmentation of a solid, brittle streambed. A detailed characterization of the bedforms that originate on the brittle substrate is provided, alongside an analysis of the correlation between bed shape and the turbulent structures of the flow. We find that turbulent fluctuations locally increase the intensity of the wall-stresses producing localized damages. The accumulation of damage drives the scouring of the solid bed via a turbulence-driven fatigue mechanism. The formation, propagation, and coalescence of scouring structures are observed. In turn, these affect both the small- and large-scale structures of the turbulent flow, producing an enhancement of turbulence intensity and wall-stresses. At the small length scales, this phenomenology is put in relation to the formation of vortical cells that persist over the peaks of the channel bed. Similarly, large-scale irregularities are found to promote the formation of stationary turbulent stripes and large-scale vortices that enhance the widening and deepening of scour holes. As a result, we observe a quadratic increment of the volumetric erosion rate of the streambed, as well as a widening of the probability density of high-intensity wall stress on the channel bed.
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Best, Jim, and Christopher R. Fielding. "Describing fluvial systems: linking processes to deposits and stratigraphy." Geological Society, London, Special Publications 488, no. 1 (2019): 152–66. http://dx.doi.org/10.1144/sp488-2019-056.
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AbstractThe period since the 1960s witnessed significant progress in our ability to decipher the clastic rock record from a wide range of sedimentary environments, and spanning many spatio-temporal scales, from millimetric to that of the sedimentary basin, and involving processes acting on timescales of seconds to millions of years. This review assesses advances in four areas of fluvial sedimentology: the nature of alluvial dunes, the role of fine-grained suspended sediment, the linking of facies models and channel planform, and the reconstruction of drainage networks within ancient sedimentary successions. The synthesis reveals that we require new thinking and research to: (1) address the range of stratification produced by dunes and their palaeohydraulic implications; (2) evolve new bedform phase diagrams capable of incorporating the reality that many fluids transport fine-grained sediment, both in flow and within the bed, which may significantly modify the bedform morphology and phase space when compared with existing bedform stability diagrams; (3) develop new alluvial facies models in which planform channel pattern is not the fundamental discriminant; and (4) re-establish consideration of process mechanics as the heart of developing ideas and debates concerning fluvial deposit preservation and alluvial architecture.
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Newson, M. D., and C. L. Newson. "Geomorphology, ecology and river channel habitat: mesoscale approaches to basin-scale challenges." Progress in Physical Geography: Earth and Environment 24, no. 2 (June 2000): 195–217. http://dx.doi.org/10.1177/030913330002400203.
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The physical component of river channel (instream) habitat is of acknowledged significance, particularly in headwater streams; furthermore, physical habitats have been heavily impacted by human needs for river services: principally flood defence (channel modification) and water resources (flow regulation). Despite the control exercised on physical habitats by fluvial geomorphology (channel shape, bed material size, bedforms and bars) and flow regime (including the varying hydraulics of flow around these forms), their interaction has hitherto lacked a distinctive spatial formulation and biological validation. This article describes the challenges faced by a need (in both theoretical and practical areas) to understand the detail of physical habitat conditions in stream channels. A number of mesoscale approaches are emerging, both from ecology and geomorphology. We outline the field validation of a ‘habitat hydraulics’ approach to the interaction between river discharge and channel form. Qualitative ‘flow types’ are shown to be representative of discrete hydraulic conditions within mesoscale units of the channel bed described as ‘physical biotopes’. The approach is compared with parallel ecological research on ‘mesohabitats’ and ‘functional habitats’. The extent, pattern and discharge-variability of physical biotopes can be surveyed in the field and used as a spatial guide to biological sampling (in this case for benthic invertebrates). Biological patterns (at the scale sampled here) appear to respond first to the river continuum concept’s longitudinal zonation of the channel, but there is a marked secondary signal in statistical analyses from the pattern of biotopes. Given the promise of the physical biotope approach, its logical extension in predictive mode is via the hierarchical concepts shared by freshwater ecologists and geomorphologists; however, there is little agreement on scale terminology, hierarchical principles and, above all, a truly geo-morphological channel classification, based on reaches, into which mesoscale habitat typologies could be fed. Assuming a relationship between biological diversity and that of physical biotopes it should be the aim of river managers, whether intervening in the channel form or its flow regime, to optimize certain parameters of the pattern of biotopes; these parameters should be a focus for future research. Both the rapid survey and proper description of these patterns will benefit from the application of remote-sensing technology, improved instruments for microscale hydraulic studies and a GIS approach based upon the spatial principles of landscape ecology.
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McMahon, William J., and Neil S. Davies. "Physical and biological functioning in Proterozoic rivers: evidence from the archetypal pre-vegetation alluvium of the Torridon Group, NW Scotland." Scottish Journal of Geology 56, no. 1 (October 11, 2019): 1–29. http://dx.doi.org/10.1144/sjg2019-013.
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In modern rivers, vegetation affects hydrological, geomorphological and sedimentological functioning, so extant fluvial systems can provide only partial analogues for those rivers that operated before the evolution of land plants. However, pre-vegetation rivers were the norm for the first 90% of Earth's history and so a better understanding of their sedimentary product can provide insights into both the fundamental underlying mechanisms of river behaviour and the ways in which fluvial processes operated on ancient Earth. In addition to a short review of the history of research into pre-vegetation alluvium, this paper presents a fieldwork-based case study of the later Proterozoic Torridon Group, which contains some of the most extensive and easily accessible exposures of pre-vegetation alluvium worldwide. Three alluvial architectural deposits have been recognized: (1) channel-bedform deposits (c. 80%); (2) barform deposits (c. 20%); and (3) out-of-channel deposits (≪1%). Channel-bedform deposits have erosional bases and most frequently stack vertically to form thick multistorey channel-bedform sequences. The preferential preservation of these deposits, which record the deepest parts of river channels, suggests that channel migration had a dominant control on preservation in the Torridon Group. Less frequently, channel-bedform deposits pass upwards into a genetically related barform deposit. Barform preservation in these instances is interpreted to be due to channel avulsion, which protected the barforms from reworking. Channel-bar thickness, measured from the basal erosional surface of a channel-bedform deposit to the top of its associated barform deposit, indicates minimum water depths of 1.7 to 8.0 m. Downstream-accreting barform deposits are most frequent, but lateral and upstream modes of accretion are also well represented. Dominant southeastward-palaeoflow directions imply that the Torridonian rivers were sourced from the Grenvillian Mountain Belt. The preserved architectural deposits and narrow dispersal of palaeocurrent data are explained by interpreting the Torridon Group as the alluvium of dominantly low-sinuosity rivers, with signatures recording autogenic fluvial adjustments. In the few rare instances where out-of-channel deposits are preserved, they contain fossil evidence for microbial mats, which prove that not all Proterozoic river systems were wholly abiotic. The overall characteristics of the Torridon alluvium, in terms of its ubiquitous highly tabular beds of sand-grade or coarser material, make it an archetypal example of pre-vegetation alluvium as known globally.Thematic collection: This article is part of the SJG Collection on Early-Career Research available at: https://www.lyellcollection.org/cc/SJG-early-career-research
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Nicholas, A. P., P. J. Ashworth, M. J. Kirkby, M. G. Macklin, and T. Murray. "Sediment slugs: large-scale fluctuations in fluvial sediment transport rates and storage volumes." Progress in Physical Geography: Earth and Environment 19, no. 4 (December 1995): 500–519. http://dx.doi.org/10.1177/030913339501900404.
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Variations in fluvial sediment transport rates and storage volumes have been described previously as sediment waves or pulses. These features have been identified over a wide range of temporal and spatial scales and have been categorized using existing bedform classifications. Here we describe the factors controlling the generation and propagation of what we term sediment slugs. These can be defined as bodies of clastic material associated with disequilibrium conditions in fluvial systems over time periods above the event scale. Slugs range in magnitude from unit bars (Smith, 1974) up to sedimentary features generated by basin-scale sediment supply disturbances (Trimble, 1981). At lower slug magnitudes, perturbations in sediment transport are generated by local riverbank and/or bed erosion. Larger-scale features result from the occurrence of rare high- magnitude geomorphic events, and the impacts on water and sediment production of tectonics, glaciation, climate change and anthropogenic influences. Simple sediment routing functions are presented which may be used to describe the propagation of sediment slugs in fluvial systems. Attention is drawn to components of the fluvial system where future research is urgently required to improve our quantitative understanding of drainage-basin sediment dynamics.
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Daryono, Sapto Kis, Sutanto Sutanto, Carolus Prasetyadi, and Eko Teguh Paripurno. "Architecture Elements of the Lemat Formation of the Lubuk Bernai Region, Batang Asam District, Tanjung Jabung Barat Regency, Jambi Province." Journal of Earth and Marine Technology (JEMT) 3, no. 1 (October 12, 2022): 1–10. http://dx.doi.org/10.31284/j.jemt.2022.v3i1.3396.
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The study of facies analysis and interpretation of the depositional environment of the Lemat Formation located at Bukit Tiga Puluh aims to clarify the problems found in Paleogene sediments in the South Sumatra Basin. A detailed analysis of the fluvial facies has been carried out in the Lubuk Bernai track. A number of observations, profiling, and measured stratigraphic section have been carried out. The stratigraphy of the study area can be divided into 5 units from old to young, namely the Mentulu-metamorphic sandstone unit, Lemat conglomerate unit, Lemat gravel-sandstone unit, Benakat volcanic-siltstone unit, and the alluvial deposit unit. The stratigraphic relationship between Mentulu metamorphic-sandstone unit and Lthe emat conglomerate unit is nonconformity. The relationship between Lthe emat conglomerate unit and Lemat gravel-sandstone unit and Benakat volcanic-siltstone unit is interfingering. The relationship between alluvial deposit units with Lemat conglomerate units and Lemat gravel-sandstone units is aan ngular unconformity. Analysis of lithofacies and architectural elements of the study area showed a fluvial depositional environment. The resulting architectural elements are 8 associations: SG (sedimentary gravity flow), GB (gravel bedform), SB (sandy bedform), CH (channel), DA (downstream accretion), HO (scour-hollow fill), AC (abandoned channel) and FF (overbank fine). The depositional environment of the Lemat Formation; Lemat conglomerate unit in alluvial fans environment, Lemat gravel sandstone unit in the shallow environment, gravel-bed braided river. In the Benakat tuffaceous-siltstone unit, it was deposited in a flashy, ephermal, sheet flood, sand-bed river environment.
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Morales, Juan A., Claudio Lozano, and Mouncef Sedrati. "Calculated Potential Bedload Versus Real Transported Sands along the Guadiana River Estuary (Spain–Portugal)." Journal of Marine Science and Engineering 7, no. 11 (November 5, 2019): 393. http://dx.doi.org/10.3390/jmse7110393.
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The Guadiana estuary is a coastal system located in the southwest of the Iberian Peninsula and is the natural border between Portugal and Spain. It is a rock-bounded estuary which extends along more than 40 km and is characterized by a semidiurnal mesotidal regime. This paper represents an approach to the bedload transport across two flow sections located in the fluvial and marine domains. In the fluvial profile, the most frequent bedform is the plane bed. In the marine area the bed of the deep channel is composed of well-sorted sand, while a lateral bar displays partially cohesive sediments with dominant fine sands in a matrix of clayey silts. Data were acquired during spring and neap tides. Near-bottom water velocities were registered by an acoustic Doppler current profiler (ADCP). Density and bed rugosity were determined in sediment samples. These data were employed using Bagnold’s equation (1963) to quantify the potential bedload (Qb). Further, real bedload values (Sb) were obtained by using Poliakoff traps. The comparison of the results of Qb under both ebb and flood conditions demonstrated a clear river-to-sea net transport in both sectors. The values of Sb were lower than those of Qb in every condition. The sand input across the fluvial estuary cannot supply the potential bedload in the lower domain of the channel, thereby causing a deficit that explains this lack of agreement between potential and real transport.
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Kurniawan, Alamsyah, Andi Egon, Karina Aprilia Sujatmiko, and Ardi Iman Malakani. "Hydrodynamic Modelling of Tidally-Influenced Fluvial Zone, a study case of Palembang, Indonesia." ILMU KELAUTAN: Indonesian Journal of Marine Sciences 27, no. 1 (March 1, 2022): 83–92. http://dx.doi.org/10.14710/ik.ijms.27.1.83-92.
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The development planning of a tidally-influenced fluvial zone poses a complex interaction between river discharge and its effect on the tidal patterns, especially in the dense population and high economic activity like Palembang located in South Sumatra Indonesia. Previous studies on numerical modelling in this area have focused on the flood; however, the hydrodynamic modelling described interaction between river discharge and tidal is not described in more detail. The present study aims to better understand the zone by using a combination of numerical modelling and qualitative assessment of in situ measurement data. Hence, the water level condition in the study area is a mix of tidal and river discharge. A 2D-hydrodynamic modeling has been successfully conducted to assess their interaction in this zone properly by using the commercial software, called MIKE21 FM. This study describes setting up the computational model, boundary location, type of forcing (tidal and non-tidal), bedform roughness, turbulent viscosity and extensive calibration and validation. In situ measurement indicates that the site's water level and flow characteristic is complex, a mixture of tidal force from the downstream and river flows from the upstream in which seasons play an important role. It is found that comparing model outputs and the measurement data in the study area for the validation and verification process effectively describes the hydrodynamic condition in the fluvial-estuarine transition area of Palembang. As the model shows good reliability, the long term hydrodynamic in line with transport model should be developed to support the Palembang area rapid development.
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Chaney, A. J., C. J. Cubitt, and B. P. J. Williams. "RESERVOIR POTENTIAL OF GLACIO-FLUVIAL SANDSTONES: MERRIMELIA FORMATION, COOPER BASIN, SOUTH AUSTRALIA." APPEA Journal 37, no. 1 (1997): 154. http://dx.doi.org/10.1071/aj96009.
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Sedimentological analysis of cored sections within the Merrimelia Formation (basal Gidgealpa Group, Cooper Basin, S.A.) reveals a complex glacigenic environment, including glacio-lacustrine, deltaic, shorezone, fluvial, aeolian and other terrestrial facies. These facies are observed within terminoglacial and proglacial environments, and interfinger constantly throughout the Merrimelia Formation, exhibiting rapid environment change related to position of the ice sheet. Detailed sedimentological and petrological analysis, suggests that Tirrawarra sandstone-type facies belongs within the Merrimelia depositional realm. Provenance data indicates that the lithic component of the Tirrawarra Sandstone, is sourced from reworked Merrimelia coeval depositional facies. A high proportion of labile grains, which are commonly observed in the Merrimelia Formation, are only observed rarely in the Tirrawarra Sandstone (sensu stricto). It is proposed that the fluvial sandstones of the Merrimelia Formation are part of the same fluvial deposystem as the Tirrawarra Sandstone (sensu stricto) and the two sandstone sequences are the natural progression of coarsening sediment as more detritus was released from melting glaciers. It is suggested that there no longer remains any sedimentological, stratigraphical or petrographical reasons why the Tirrawarra Sandstone should not be included within the Merrimelia Formation. It is further proposed that all the braided glacio- fluvial sandstones within the Merrimelia Formation and Tirrawarra Sandstone (sensu stricto) be grouped together as 'Tirrawarra-type' facies within the Merrimelia glacigenic domain.The concept that the glacio-fluvial sandstones within the Merrimelia Formation are of the same genetic origin as the Tirrawarra Sandstone (sensu stricto), must point to the economic potential of similar sandstones found throughout the Merrimelia Formation. The thickness, sediment style and lateral extent of the proglacial braidplains is controlled by the duration of glacial melting. The Merrimelia Formation reveals a sequence of major freezing and thawing episodes with the overlying Patchawarra Formation representing the cessation of glacial influence in the Cooper Basin. Therefore, the youngest 'Tirrawarra-type' sandstone facies found at the top of the Merrimelia Formation is likely to contain the least amount of labile grains, a highly rigid siliceous framework and will be well sorted. The risk of lower reservoir quality increases down section where, with time, freezing dominated over thawing and the sediments were less rinsed, and where the resultant sandstones are more likely to be thin, more poorly sorted and chemically immature with a high proportion of labile framework grains. Thus compositional variation, controlling the diagenetic overprint, together with sandstone facies and bedform style exert profound control on the reservoir quality in the Tirrawarra-Moorari Field area, on potential gas reservoirs in the Merrimelia Formation.
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Le Guern, Jules, Stéphane Rodrigues, Thomas Geay, Sébastien Zanker, Alexandre Hauet, Pablo Tassi, Nicolas Claude, Philippe Jugé, Antoine Duperray, and Louis Vervynck. "Relevance of acoustic methods to quantify bedload transport and bedform dynamics in a large sandy-gravel-bed river." Earth Surface Dynamics 9, no. 3 (May 27, 2021): 423–44. http://dx.doi.org/10.5194/esurf-9-423-2021.
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Abstract. Despite the inherent difficulties in quantifying its value, bedload transport is essential for understanding fluvial systems. In this study, we assessed different indirect bedload measurement techniques with a reference direct bedload measurement in a reach of a large sandy-gravel-bed river. An acoustic Doppler current profiler (aDcp), the dune tracking method (DTM) and hydrophone measurement techniques were used to determine bedload transport rates by using calibration with the reference method or by using empirical formulas. This study is the first work which attempted to use a hydrophone to quantify bedload rates in a large sandy-gravel-bed river. Results show that the hydrophone is the most efficient and accurate method for determining bedload fluxes in the Loire River. Although further work is needed to identify the parameters controlling self-generated sediment noise, the calibration procedure adopted in this study allows a satisfactory estimation of bedload transport rates. Moreover, aDcp and hydrophone measurement techniques are accurate enough to quantify bedload variations associated with dune migration.
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GASTALDO, R. A. "The Relationship Between Bedform and Log Orientation in a Paleogene Fluvial Channel, Wei elster Basin, Germany: Implications for the Use of Coarse Woody Debris for Paleocurrent Analysis." PALAIOS 19, no. 6 (December 1, 2004): 587–97. http://dx.doi.org/10.1669/0883-1351(2004)019<0587:trbbal>2.0.co;2.
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DAVIES, NEIL S., JOHN C. GOSSE, ALEXANDRA ROUILLARD, NATALIA RYBCZYNSKI, JIN MENG, ALBERTO V. REYES, and JARLOO KIGUKTAK. "WOOD JAMS OR BEAVER DAMS? PLIOCENE LIFE, SEDIMENT AND LANDSCAPE INTERACTIONS IN THE CANADIAN HIGH ARCTIC." PALAIOS 37, no. 6 (June 28, 2022): 330–47. http://dx.doi.org/10.2110/palo.2021.065.
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ABSTRACT During the mid-Pliocene (Zanclean, ca. ∼ 3.9 Ma), parts of the Canadian High Arctic experienced mean annual temperatures that were 14–22°C warmer than today and supported diverse boreal-type forests. The landscapes of this vegetated polar region left behind a fragmented sedimentary record that crops out across several islands in the Canadian Arctic Archipelago as the Beaufort Formation and correlative strata. Paleoecological information from these strata provides a high-fidelity window onto Pliocene environments, and prominent fossil sites yield unparalleled insights into Cenozoic mammal evolution. Significantly, many of the strata reveal evidence for life-sediment interactions in a warm-climate Arctic, most notably in the form of extensive woody debris and phytoclast deposits. This paper presents original field data that refines the sedimentological context of plant debris accumulations from the anactualistic High Arctic forests, most notably at the ‘Fyles Leaf Beds' and ‘Beaver Pond' fossil-bearing sites in the ‘high terrace deposits' of central Ellesmere Island. The former is a remarkably well-preserved, leaf-rich deposit that is part of a complex of facies associations representing lacustrine, fluvio-deltaic and mire deposition above a paleotopographic unconformity. The latter yields tooth-marked woody debris within a peat layer that also contains a rich assemblage of vertebrate and plant fossils including abundant remains from the extinct beaver-group Dipoides. Here we present sedimentological data that provide circumstantial evidence that the woody debris deposit at Beaver Pond could record dam-building in the genus, by comparing the facies motif with new data from known Holocene beaver dam facies in England. Across the Pliocene of the High Arctic region, woody debris accumulations are shown to represent an array of biosedimentary deposits and landforms including mires, driftcretions, woody bedforms, and possible beaver dams, which help to contextualize mammal fossil sites, provide facies models for high-latitude forests, and reveal interactions between life and sedimentation in a vanished world that may be an analogue to that of the near-future.
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Koller, Débora Karine, Ana Luiza de Oliveira Borges, Eduardo Puhl, and Rafael Manica. "Prediction of the bedforms generated by density currents based on fluvial phase diagrams." RBRH 22 (September 18, 2017). http://dx.doi.org/10.1590/2318-0331.0217160021.
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ABSTRACT Density currents, whose movement takes place by the density difference between the flow and the ambient fluid around it, can interact with the substract generating bedforms similar to the fluvial environments. However, there are no specific bedform phase diagrams capable to predict this type of phenomenon. This study aims to compare the prediction of fluvial bedforms phase diagram with those generated by experimental saline currents. Bedforms were generated in two-dimensional tilting plexiglass flume submerged in a larger tank filled with water with three different mobile beds and varied values of discharge and salt concentration. It was observed three types of bedform (lower plane bed, ripples and dunes), which, with the concomitant calculation of hydrodynamic parameters (mean velocity, energy and mobility) allowed the use of the phase diagram. It was observed that the fluvial phase diagrams did not present good predictions for bedforms generated by density currents. This fact is associated to the hydrodynamics differences (velocity and concentration profiles) and the limitation of the dimensional parameters in the extrapolation of results. Therefore, it is indicated the need to draw up a proper phase diagram to density currents.
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Branß, Till, Francisco Núñez-González, and Jochen Aberle. "Fluvial levees in compound channels: a review on formation processes and the impact of bedforms and vegetation." Environmental Fluid Mechanics, April 2, 2022. http://dx.doi.org/10.1007/s10652-022-09850-9.
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AbstractNatural levees are wedge-shaped morphological features developing along the boundaries of mass flows. When they form in fluvial landscapes, they can have multiple implications for river management of trained inland rivers. This paper summarizes the present knowledge in regard to the formation and evolution of so-called fluvial levees of trained inland river sections and provides novel hypotheses in regard to the significance of bedforms and vegetation strips along the floodplain on levee formation, evolution, and characteristics. The hypotheses that (i) bedforms contribute to levee formation by altering the interface hydraulics between the main channel and the floodplain and enhancing entrainment of sediment into suspension and (ii) vegetation stripes along the floodplain additionally affect the interface hydraulics resulting in a changed levee geometry are supported by combining existing knowledge on bedform dynamics and flow-vegetation-sediment interaction with results reported in recent flume studies.
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Guala, M., M. Heisel, A. Singh, M. Musa, D. Buscombe, and P. Grams. "A Mixed Length Scale Model for Migrating Fluvial Bedforms." Geophysical Research Letters 47, no. 15 (August 3, 2020). http://dx.doi.org/10.1029/2019gl086625.
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Ulak, Prakash Das. "Paleohydrological reconstruction of the Siwalik Group along the Tinau Khola section, west-central Nepal Himalaya." Journal of Nepal Geological Society 39 (September 25, 2009). http://dx.doi.org/10.3126/jngs.v39i0.31485.
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Neogene fluvial sedimentary sequences of the Siwalik Group are extensively accumulated in the southern frontal part of the Himalaya and well exposed in the Tinau Khola section of the west-central Nepal Himalaya. The group reveals a coarsening upwards succession in general but many fining-upwards fluvial successions on a scale from several to tens of metres is established in each lithological unit. The paleohydrological characteristics have been estimated using thickness of fining upwards fluvial successions, their grain diameters, and bedforms. The paleohydrology suggests an increase in flow velocity, channel slope gradient, and discharge of the fluvial system. Paleovelocity varies from 0.17 to 5.31 m/s, paleochannel gradient and paleodischarge change from l.13x10-5 to 7.33x10-4 m/m and 101 to 104 m3/s, respectively towards the stratigraphic top. These progressively changing paleohydrological characteristics reflect the southward propagation of thrusts caused by the upheaval of the Himalaya.
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Cardenas, Benjamin T., Michael P. Lamb, Zane R. Jobe, David Mohrig, and John M. Swartz. "Morphodynamic Preservation of Fluvial Channel Belts." Sedimentary Record 21, no. 1 (January 19, 2023). http://dx.doi.org/10.2110/001c.66285.
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The fluvial sedimentary record is largely composed of deposits from relatively common flow events, rather than more catastrophic scour-and-fill events. At the scales of bedforms, such deposits are preserved within the stratigraphic record because they rapidly accumulate within, and are protected by, morphodynamic topographic depressions that occur naturally in the fluvial system as a result of feedbacks between flow, sediment transport, and topography. Examples include the preservation of ripples in front of dunes, dunes in front of bars, and bars within channels. Here, we used 3D seismic data that images preserved channel belts to test the hypothesis that alluvial-ridge basins, morphodynamic depressions formed between raised channel beds due to decreasing sedimentation rates away from channels in alluvial settings, are a source of topography driving channel-belt-scale preservation. Using the 3D seismic data, we measured the stratigraphic positions of channel belts, as well as their lengths, widths, sinuosities, and centerline orientations in the 3D seismic dataset. Results are consistent with well-preserved channel belts steered by alluvial-ridge-basin topography. Further, the thickness of the channel-belt interval exceeds the relief of any one alluvial-ridge basin, suggesting the volume records the filling of multiple alluvial-ridge basins and that the process is common. Characterizing the stratigraphic signature of alluvial-ridge basins is necessary for understanding contrasting fluvial architectures where external forcings prevented their formation.
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Wörman, Anders, Aaron I. Packman, Lars Marklund, Judson W. Harvey, and Susa H. Stone. "Fractal topography and subsurface water flows from fluvial bedforms to the continental shield." Geophysical Research Letters 34, no. 7 (April 4, 2007). http://dx.doi.org/10.1029/2007gl029426.
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Ulak, Prakash Das, and Katsuhiro Nakayama. "Neogene fluvial systems in the Siwalik Group along the Tinau Khola section, west central Nepal Himalaya." Journal of Nepal Geological Society 25 (December 1, 2001). http://dx.doi.org/10.3126/jngs.v25i0.32072.
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Along the Tinau Khola section of west central Nepal, the Siwalik Group is a 4 km thick pile of fluvial sedimentary sequence of mudstone, sandstone and conglomerate. It is exposed between the Main Boundary Thrust (MBT) to the north and the Frontal Churia Thrust (FCT), also known as the Main Frontal Thrust (MFT), in the south. The Siwalik Group is lithologically divided into the Arung Khola, Binai Khola and Chitwan formations, in ascending order. Six facies associations (FA1 to FA6) are recognised within the group based on grain size distribution, nature of bedforms, and sandstone-mudstone ratio. The fine-grained sediments of the Lower and Middle members of the Arung Khola Formation belong to the FA1-facies association and were interpreted to have deposited by a low-discharge, low -relief meandering fluvial system. The multiple accumulated thin-layered muddy sandstone sequence in the Upper Member of the Arung Khola and the Lower Member of the Binai Khola formations belong to FA2 and FA3- facies associations and were deposited by a flood flow-dominated meandering fluvial system. The deep sandy braided facies association (FA4) and shallow sandy braided facies association (FA5) are well developed in the Middle and Upper members of the Binai Khola Formation, respectively. The gravelly braided facies association (FA6) is recognised in the Chitwan Formation.
The palaeomagnetically well-studied section of the Tinau Khola allows precise dating of the major change of fluvial system during the deposition of the Siwalk Group. The environment of predominantly shallow meandering rivers with low relief and low-discharge during the time of deposition of the Arung Khola Formation changed at 9.9 Ma and flooding in the rivers dramatically increased due to the intensification of monsoon precipitation. This hydrographic change also brought the change in facies from the earlier FA1 facies to FA2 and FA3 facies. Change from meandering to braided system occurred at 8.2 Ma because of the obvious regional tectonic upliftment of the Higher Himalaya bringing into FA4 and FA5-facies associations. Finally the FA6-facies association was developed due to the large gravelly braided system development at 2.5 Ma as a result of the Main Boundary Thrust movement along the frontal part of the Himalaya.
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Flemming, Burg, and Keith Martin. "The Breede River estuary (Cape Province, South Africa): A historical perspective on hydrology, geomorphology, and sedimentology." Geo-Marine Letters 41, no. 1 (February 25, 2021). http://dx.doi.org/10.1007/s00367-021-00686-8.
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AbstractA hitherto unpublished historical dataset of the Breede River estuary, Western Cape, South Africa, that was collected in the summer season of 1983 is presented. Bathymetric, physiographic, and sedimentological data were collected at 1–1.5-km intervals between the mouth and the Malgas ferry crossing at km 35. The remaining estuary up to km 52 was not surveyed. Sedimentologically, the estuary could be divided into a lower marine sand reach (mouth to km 5), a mixed sand/mud reach (km 5–18.5), and a fluvial sand reach upstream of km 18.5. Hydrological data were collected at three midstream anchor stations (mouth, km 14.5, and km 24) which were occupied for complete tidal cycles. Five parameters were recorded: tidal elevation, current velocity, salinity, temperature, and light transmittance. Pronounced velocity asymmetries of the tides were revealed by phase delays between the times of low (high) water and corresponding slack water (turn of the tide), as well as considerable up-estuary delays in the occurrence of high and low tides. The mode of tidal wave propagation was synchronic (constant height) up to a distance of ~23 km at spring high tide and ~13 km at neap high tide, from where it proceeded in hyposynchronic mode (progressive decrease in height). Peak surface velocities reached 1.5 m/s at Station 1 (mouth), 0.6 m/s at Station 2 (km 14), and 0.45 m/s at Station 3 (km 24). The marine sand reach and parts of the mixed sand/mud and fluvial sand reaches were distinctly flood dominated as revealed by the orientation of bedforms. Salt water intrusion reached up to km 25, where river background levels were reached. Suspended sediment concentrations (turbidity) varied from 55–85 mg/l at the mouth, 65–200 mg/l in the mixed sand/mud reach, and 55–85 mg/l in the fluvial sand reach. At the time of observation, the Breede River estuary was in a well-mixed hydrological state. The fluvial sand reach displayed numerous, up to 18-m-deep scour pools. Grain-size distributions revealed distinct differences between the individual estuary sections, the sand/mud, and marine sand reaches, in particular, being characterized by up to four, mostly mixed hydraulic populations. Offshore seismic profiles suggest that the Duiwenhoks River, located 14 km to the east of the Breede mouth, was a tributary of the latter during Pleistocene sea-level lowstands. From a global perspective, the Breede River estuary conforms physically to typical small estuaries that are only marginally impacted by human interferences.
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Flor-Blanco, G., G. Flor, and L. Pando. "Dynamics and sedimentary assessment of a rock-bounded estuary: a case study—Tina Mayor (NW Spain, Iberian Peninsula)." Environmental Earth Sciences 81, no. 13 (June 25, 2022). http://dx.doi.org/10.1007/s12665-022-10471-0.
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AbstractBased on a comprehensive study of the Tina Mayor estuary, a conceptual morphosedimentary model is proposed for one of the best-preserved limestone sectors of the Iberian Peninsula. This mesotidal and rock-bounded estuary consists of a significant proportion of quartzitic gravel fractions, which is distinctive compared to the other nearby estuaries of Northwest Spain on the Iberian Peninsula. Fluvial discharges allow for high coarse fraction inputs to be distributed to all the geomorphological estuarine zones, particularly the mouth, the bay and the inner areas. Moreover, the narrowing of the rocky boundary affects the outermost sector of the mouth of the estuary, developing two coarse grain spits; the inner being much more extensive, while tidal flats occupy a greater reclaimed area than the natural ones. The dominant sedimentary flow regime was established based on tidal and current records during a tidal cycle. The flood currents crossing the bay change trajectory at the mouth boundary as a result of rocky narrowing from the western mouth to the eastern inner side in a reverse response to the Coriolis effect. Estuarine morphosedimentary units are mapped, including the large and minor bedforms in each estuarine zone. These have been characterised according to the average values of the granulometric parameters (coarsest 1-percentile grain size or centile, mean size, sorting, skewness and kurtosis), as well as the carbonate (bioclast) percentage, including the trend maps of the mean size, sorting and biogenic carbonate content. Furthermore, taking into account the mean tidal amplitude and mixing waters (QF/QT), a suitable classification can be established for any type of estuary, including the characteristics of the confinement of the estuary mouth.
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Griffis, N., R. Mundil, I. Montanez, D. Le Heron, P. Dietrich, and R. Iannuzzi. "A Carboniferous Apex for the late Paleozoic Icehouse." Geological Society, London, Special Publications 535, no. 1 (February 2023). http://dx.doi.org/10.1144/sp535-2022-256.
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Abstract Icehouse climate systems occur across an abbreviated portion of Earth history, comprising ∼25% of the Phanerozoic record. The Late Paleozoic Ice Age (LPIA) was the most extreme and longest lasting glaciation of the Phanerozoic and is characterized by periods of acute continental scale glaciation, separated by periods of ice minima or ice-free conditions on the order of <10 6 years. The late Paleozoic glaciogenic record of the Paraná and Kalahari basins of southern Gondwana form one of the largest, best preserved, and well calibrated records of this glaciation. In the Carboniferous, the eastern and southern margins of the Paraná Basin and the Kalahari Basin were characterized by subglacial conditions, with evidence for continental and upland glaciers. In the latest Carboniferous, these basins transitioned from subglacial reservoirs to ice-free conditions evidenced by the widespread deposition of marine deposits juxtaposed on subglacial bedforms. High-precision U-Pb zircon CA-TIMS geochronologic constraints from volcanic ash deposits in the deglacial marine black shales of the Kalahari Basin and from fluvial and coal successions, which overlie marine deposits in the Paraná, indicate subglacial evidence in these regions is constrained to the Carboniferous. The loss of ice in these regions is congruent with a late Carboniferous peak in p CO 2 and widespread marine anoxia in the late Carboniferous. The permeant retreat of glaciers in basinal settings, despite an early Permian p CO 2 nadir, highlight the influence of short-term perturbations on the longer-term CO 2 record and suggests an ice-threshold had been crossed in the latest Carboniferous. A definitive driver for greenhouse gases in the LPIA, such as abundant and sustained volcanic activity or an increased biologic pump driven by ocean fertilization, is unresolved for this period. Lastly, the proposed Carboniferous apex for the high-latitude LPIA record is incongruent with observations from the low-latitude tropics where an early Permian peak is proposed.
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Leary, Kate C. P., and Vamsi Ganti. "Preserved Fluvial Cross Strata Record Bedform Disequilibrium Dynamics." Geophysical Research Letters 47, no. 2 (January 20, 2020). http://dx.doi.org/10.1029/2019gl085910.
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