Toggling between expansion and translation

Johnston, Shelby Lynn; Holbrook, John

doi:10.1002/9781119424437.ch3

Cited by 11 publications

(6 citation statements)

References 61 publications

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“…This may reflect the effect of toggling between expansion and translation on intra-point bar erosion (cf. Johnston & Holbrook, 2019), for example, as seen in Case 18 (Figure S1).…”

Section: Resultsmentioning

confidence: 68%

“…This likely reflects how the rate of erosion of developing point bars remains relatively steady in time under conditions of constant style of meander transformation; this situation may be best depicted by meanders undergoing progressive bend tightening. When changes of meander transformation styles occur, instead, more significant intra-point-bar erosion commonly takes place (Durkin et al, 2018;Hagstrom et al, 2019;Johnston & Holbrook, 2019). Significant erosion can occur when formerly expansional meanders commence a trajectory of downstream migration, for example, where channel banks encounter less erodible substrates, such as valley walls or abandoned channel fills (Ghinassi et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

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Evaluation of Morphodynamic Controls on the Preservation of Fluvial Meander‐Belt Deposits

Yan

Colombera

Mountney

2021

Geophysical Research Letters

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“…This may reflect the effect of toggling between expansion and translation on intra-point bar erosion (cf. Johnston & Holbrook, 2019), for example, as seen in Case 18 (Figure S1).…”

Section: Resultsmentioning

confidence: 68%

Section: Discussionmentioning

confidence: 99%

Evaluation of Morphodynamic Controls on the Preservation of Fluvial Meander‐Belt Deposits

Yan

Colombera

Mountney

2021

Geophysical Research Letters

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“…The rarity of compound, UFR‐dominated lateral and mid‐channel bars likely also reflects highly erosive and chaotic scour during discrete storm discharges and reflects the challenges this condition poses to maintaining the steady and repetitive flow that contributes to bar accretion and migration. In contrast, compound lateral and midchannel bars are typical and prevalent in perennial lower‐flow‐regime channels with more protracted flows and less variable discharge conditions that do not tend to scour and clear entire channel sectors during discrete flood events (Leopold & Wolman, 1957; Blondeaux & Seminara, 1985; Bridge, 2003; Moody & Meade, 2014; Johnston & Holbrook, 2018). However, channel filling by low‐angle, approximately transverse bars accreted from single or multiple flood events (Plink‐Björklund, 2015; Wang & Plink‐Björklund, 2019) occurred in at least some Dockum channels (Figs 4C and 10).…”

Section: Architectural Elementsmentioning

confidence: 99%

Structures, architecture, vertical profiles, palaeohydrology and taphonomy of an upper‐flow‐regime‐dominated fluvial system, the Triassic Dockum Group of the Palo Duro Canyon, Texas

Walker

Holbrook

2022

Sedimentology

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Triassic strata of the Tecovas and Trujillo formations in the Palo Duro Canyon of West Texas record deposition dominated throughout by upper‐flow‐regime channel flow. These strata provide an opportunity for new insights into the architecture, floodplain/channel processes, vertical profiles, palaeohydrology and taphonomy typical of broader upper‐flow‐regime‐dominated fluvial systems. Thicker channel‐fills (ca 2 m, aspect ratio ca 24) host upper‐plane‐bed, symmetrical antidune, breaking‐antidune, chute‐and‐pool, and cyclic‐step structures. The thinner channel‐fill population (<1 m, aspect ratio ca 35) comprises upper‐plane‐bed and some antidune structures. Some of the larger channel fills developed low‐angle downstream‐accreting bars, with rare examples of laterally accreting side‐attached bars. This appears to be the first documentation of an ancient upper‐flow‐regime side‐attached bar. Lamina orientation of structures parallel accretion surfaces because these followed the original bed surface, and structures drop in flow regime down the bar surfaces as formative Froude numbers also declined. A generalized vertical sequence for large upper‐flow‐regime channel storeys has upper‐plane‐bed structures above the basal scour, transitioning upward into higher flow regime structures (for example, antidunes, cyclic steps, etc.), then back to a mix of upper‐plane‐bed and antidunes or lower‐flow‐regime structures towards the top. The Tecovas Formation and overlying Trujillo Sandstone both bear layers of cross‐cutting laterally amalgamated valley fills, multivalleys, and are separated by a regional sequence boundary. Calculated palaeodischarges for Tecovas (ca 90 m3/s) and Trujillo (ca 76 m3/s) rivers record flow at the stage where symmetrical antidunes were deposited. These discharges occurred at some point on the falling limb of a flood hydrograph of currently unknown shape. Slopes for the rivers were on the order of 10−4 to 10−5, consistent with typical continental‐interior rivers. Large and flashy discharge was, thus, the likely cause for supercritical‐flow conditions instead of excessive slopes. Rivers in both the Tecovas and Trujillo formations record a fluvial system developed in a tropical to subtropical megamonsoonal environment. The tendency for preservation of metre‐scale channel‐fills and catastrophic inundations of floodplains and lakes in single floods has also made the Dockum Group a prolific preserver of large Triassic vertebrates.

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“…Although rivers with high suspended load and seasonal discharge can produce mud‐rich and cyclically‐organized deposits (Jablonski & Dalrymple, 2016; Johnston & Holbrook, 2019; Simon et al ., 2019), the abundance of mud and the rhythmic deposition are commonly considered as a signature of tidal processes (Bridges & Leeder, 1976; Barwis, 1978; Boersma & Terwindt, 1981; De Mowbray, 1983; Terwindt, 1988; Kvale et al ., 1989; Tessier & Gigot, 1989; Choi et al ., 2004; Pearson & Gingras, 2006; Santos & Rossetti, 2006; Dalrymple & Choi, 2007; Hubbard et al ., 2011; Fustic et al ., 2012; Kvale, 2012; Croix & Dashtgard, 2014, 2015; Rossi et al ., 2017). In tidal environments, mud can occur: (i) as laminae which define sedimentary structures (Van Straaten, 1954; Reineck, 1970; Dalrymple et al ., 1991; Tessier, 1993; Choi, 2010, 2011; Martinius & Van den Berg, 2011); (ii) as layers (for example, fluid mud Harris et al ., 2004; Ichaso & Dalrymple, 2009; Longhitano et al ., 2012; Chen et al ., 2015); and (iii) as intervals within the inclined heterolithic stratification (Bridges & Leeder, 1976; Barwis, 1978; De Mowbray, 1983; Thomas et al ., 1987; Choi et al ., 2004, 2013; Fagherazzi et al ., 2004; Rebata‐H.…”

Section: Introductionmentioning

confidence: 99%

Sedimentology of a hypertidal point bar (Mont‐Saint‐Michel Bay, north‐western France) revealed by combining lidar time‐series and sedimentary core data

et al. 2021

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Intertidal meanders developed on salt marshes are known to expand and produce inclined heterolithic stratification rich in fine‐grained sediments and to bear evidence for rhythmic deposition in the upper part of the inner meander bend (i.e. the upper part of the point bar). This occurs because the lower point‐bar deposits are washed by strong currents, which remove mud drapes and develop discontinuous record of tidal cycles. Although these criteria are widely accepted, facies models for tidal point bars still lack a three‐dimensional perspective and overlook the along‐bend variability of sediment distribution. The present study focuses on a hypertidal point bar belonging to the upper‐intertidal domain of the Mont‐Saint‐Michel Bay (France), and it analyses the sedimentology of a 3D time‐framed accretionary package formed between 28 March 2012 and 29 November 2012 by means of lidar topographic data, geomorphological field surveys and sedimentological core data. To define the 3D time‐framed accretionary package, data from thirteen lidar (light detection and ranging) topographic surveys were used to create the point‐bar synthetic stratigraphy. Data show that over the study period the point bar expanded alternating deposition along its seaward and landward sides, pointing out the occurrence of depositional patterns more complex than a simple progressive expansion of the bend. The thickest deposits were accumulated in the point‐bar‐apex zone, where the largest amount of mud was also stored. High sediment accretion in the bend‐apex zone is ascribed to the development of low‐energy conditions due to flow and bed configuration. High accretion rate of the point‐bar‐apex zone promoted also a better preservation of rhythmites, which are almost missing from deposits accumulated along the point‐bar sides. This study remarks that preservation of mud and tidal rhythmites within intertidal‐point‐bar deposits is controlled, not only by their elevation with respect to the tidal range, but also by their location along the point bar.

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Toggling between expansion and translation

Cited by 11 publications

References 61 publications

Evaluation of Morphodynamic Controls on the Preservation of Fluvial Meander‐Belt Deposits

Evaluation of Morphodynamic Controls on the Preservation of Fluvial Meander‐Belt Deposits

Structures, architecture, vertical profiles, palaeohydrology and taphonomy of an upper‐flow‐regime‐dominated fluvial system, the Triassic Dockum Group of the Palo Duro Canyon, Texas

Sedimentology of a hypertidal point bar (Mont‐Saint‐Michel Bay, north‐western France) revealed by combining lidar time‐series and sedimentary core data

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