Generic autogenic behaviour in fluvial systems

Postma, George

doi:10.1002/9781118920435.ch1

Cited by 11 publications

(9 citation statements)

References 54 publications

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“…The cyclic‐step hypothesis is further corroborated by the characteristic facies transitions from structureless and deformed facies to well‐stratified facies within the accretion sets. Such transitions have been rendered characteristic in upstream‐migrating cyclic steps (Postma et al., ; Postma & Cartigny, ; Postma, ). Cyclic steps migrate upstream as erosion occurs in supercritical‐flow conditions upstream of a hydraulic jump, whereas high rates of deposition occur at the transition to subcritical flow downstream (Kostic & Parker, ; Cartigny et al., ) (Fig.…”

Section: Channel Macroformsmentioning

confidence: 99%

“…Backsets form at the downstream edge of the hydraulic‐jump scour when the hydraulic jump migrates upstream at a steady rate (Ono et al., ). The highest deposition rates occur at the hydraulic jump, resulting in structureless or graded deposits (Postma et al., ; Postma & Cartigny, ; Postma, ) (Fig. B and C).…”

Section: Channel Macroformsmentioning

confidence: 99%

“…Cartigny et al., ). Upstream migration of a hydraulic jump then results in a vertical succession where erosional scours are overlain by structureless deposits (F1.8) that transition upward into better stratified deposits, such as F1.3, F1.5, F1.6 and F2.2 (Postma et al., ; Postma & Cartigny, ; Postma, ). However, structureless facies (F1.8) as well as soft‐sediment deformation (F1.9) can also be linked to partial collapse and slumping of the hydraulic‐jump scour walls, such as demonstrated during experiments (Cartigny et al., ).…”

Section: Channel Macroformsmentioning

confidence: 99%

See 2 more Smart Citations

Variable‐discharge‐river macroforms in the Sunnyside Delta Interval of the Eocene Green River Formation, Uinta Basin, USA

Wang

Plink‐Björklund

2020

Sedimentology

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An outcrop dataset from the early Eocene Sunnyside Delta Interval of the Green River Formation in the Uinta Basin, Utah, USA, documents alluvial channel lithosomes. The abundance of Froude supercritical-flow sedimentary structures, together with an abundance of high-deposition-rate sedimentary structures, in-channel bioturbation and pedogenic modification, in-channel muds and thick soft-clast conglomerates, identify these lithosomes as deposits of variable-discharge rivers. These recognition criteria are part of an emerging facies model for variable-discharge rivers. This facies model, however, yet lacks robust recognition criteria for macro-scale or bar-scale stratal patterns of variable-discharge rivers. This study presents a dataset that corroborates some known stratal patterns and provides examples of hitherto unknown bar-scale stratal patterns of variable-discharge rivers, including: (i) low-angle downstream-accretion sets that may form as washed-out sheets in high sediment supply conditions or downstream of hydraulic jumps; (ii) high-angle upstreamaccretion sets that imply deposition from systematically upstream-migrating channel-scale hydraulic jumps (cyclic steps); (iii) concave-up, upward-flattening high-angle downstream-accretion sets that are consistent with aggradation in channel-scale hydraulic-jump scours; (iv) upstream-accretion and lateralaccretion sets that may be linked to high-magnitude flood reworking of point bars; and (v) aggradation or vertical-accretion sets of ambiguous origin. These unconventional stratal patterns are compared to the established bar strata, such as those formed by point bars and braid bars and a discussion is provided on formative conditions for the here documented unconventional strata. This work highlights a need for further studies on the effect of discharge variability on bar formation and on the link between river morphology and bar types.

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Section: Channel Macroformsmentioning

confidence: 99%

Section: Channel Macroformsmentioning

confidence: 99%

Section: Channel Macroformsmentioning

confidence: 99%

See 1 more Smart Citation

Variable‐discharge‐river macroforms in the Sunnyside Delta Interval of the Eocene Green River Formation, Uinta Basin, USA

Wang

Plink‐Björklund

2020

Sedimentology

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“…However, understanding autogenic dynamics that act over longer timescales (centuries and longer) requires other approaches like reduced-scale physical and numerical experiments-which allow us to effectively speed up time (Paola et al 2009)-along with studies of ancient sedimentary deposits that record real-world case studies of landscape and seascape dynamics. Insights from physical and numerical experiments have produced hypotheses about the nature of and controls on sedimentary autogenics (e.g., Muto & Steel 2004;Kleinhans 2005;Kim et al 2006Kim et al , 2014Jerolmack & Paola 2007;Clarke et al 2010;Reitz et al 2010;Straub & Esposito 2013;Straub & Wang 2013;Karamitopoulos et al 2014;Postma 2014;Li et al 2016), which have more recently begun to be tested in field settings (Hajek et al 2010Hofmann et al 2011;Straub & Pyles 2012;Flood & Hampson 2014;Reitz et al 2015;Hampson 2016). Physical controls on autogenic dynamics in fluvial-deltaic systems have been particularly well studied, and scaling approaches have helped overcome limitations associated with often poor absolute age dating in deep time stratigraphy.…”

Section: Approaches To Studying Autogenic Dynamicsmentioning

confidence: 99%

Autogenic Sedimentation in Clastic Stratigraphy

Hajek

Straub

2017

Annu. Rev. Earth Planet. Sci.

127

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Internally generated, or autogenic, terrestrial and marine sediment-transport dynamics can produce depositional patterns similar to those associated with climatic, tectonic, or sea level changes. A central challenge in accurately interpreting the sedimentary archive is determining what scales and types of deposits reflect autogenic controls on sedimentation in different environments. Autogenic sediment-transport dynamics commonly result from intermittent sediment storage in transient landforms, which produces episodic, spatially discontinuous sedimentation across a basin. The transition from localized, variable sedimentation to even, basin-wide sedimentation marks the shift from stochastic landscape dynamics to deterministic deposition responding to the long-term balance between sediment supply and the creation of space to accommodate sediment. This threshold can be measured in a wide variety of stratigraphic successions and has important bearing on whether climatic, tectonic, or sea level signals can be recognized in physical sedimentary deposits.

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“…Prior studies recognized the importance of an acceleration term for stratigraphic signals, specifically the completeness of the stratigraphic record (Sadler & Strauss, 1990). The general idea is that a rapid change in sediment supply, even if small in total magnitude, can trigger a transient response at the Earth's surface, as the system is unable to remain in equilibrium with forcing conditions (Postma, 2014). If the period of the signal is short, it might not produce a thick enough sedimentary response to withstand reworking prior to burial beneath the active surface.…”

Section: Storage Of Geomorphic Signals In Stratigraphymentioning

confidence: 99%

A Stratigraphic Framework for the Preservation and Shredding of Environmental Signals

Toby

Duller

Angelis

et al. 2019

Geophysical Research Letters

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The stratigraphic record contains unique information about past landscapes and environmental change. Whether landscapes faithfully transmit signals of environmental change to stratigraphy is unknown because autogenic processes, such as river avulsion, can obscure signals prior to long‐term stratigraphic storage. We develop a theoretical framework that predicts when a sediment flux signal will be transferred from the landscape to stratigraphy. This threshold magnitude is a function of signal duration. The magnitude is set by the maximum rate of autogenic volume change of the landscape, which decreases with increasing time window. Physical delta experiments, specifically designed to test our theory, demonstrate that only sediment supply signals with a magnitude greater than the threshold are stored in stratigraphy, supporting our theory. This framework allows us to assess the fidelity of the stratigraphic record to archive past signals of environmental change and predict the short‐ and long‐term impact of current anthropogenic forcing on landscapes.

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Generic autogenic behaviour in fluvial systems

Cited by 11 publications

References 54 publications

Variable‐discharge‐river macroforms in the Sunnyside Delta Interval of the Eocene Green River Formation, Uinta Basin, USA

Variable‐discharge‐river macroforms in the Sunnyside Delta Interval of the Eocene Green River Formation, Uinta Basin, USA

Autogenic Sedimentation in Clastic Stratigraphy

A Stratigraphic Framework for the Preservation and Shredding of Environmental Signals

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