Antecedent Topography and Sediment Dispersal: The Influence of Geologically Instantaneous Events on Basin Fill Patterns

Sincavage, R.; Liang, Man; Pickering, Jennifer; Goodbred, S. L.; Passalacqua, Paola

doi:10.1029/2021jf006539

Cited by 2 publications

(2 citation statements)

References 96 publications

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“…Cardenas et al (2023) suggested major shifts in boundary conditions may disrupt this underlying morphodynamic control on avulsion patterns. Sincavage et al (2022) presents evidence that the Bahmaputra River has preferentially filled Holocene palaeochannels generated by outburst floods rather than the topographically favourable course into the Sylhet Basin of Bangladesh. In the Bighorn Basin, the extreme outlier in the multi‐story sandbody data set (Figure 4) is found within the PETM climate event (Foreman, 2014).…”

Section: Discussionmentioning

confidence: 99%

Flow depth estimates and avulsion behaviour in alluvial stratigraphy (Willwood Formation, Bighorn Basin, Wyoming, USA)

Foreman,

Sutherland,

Todd

et al. 2023

The Depositional Record

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The size and geometry of river channels play a central role in sediment transport and the character of deposition within alluvial basins across spatiotemporal scales spanning the initiation of grain movement to the filling of accommodation generated by subsidence. This study compares several different approaches to estimating palaeoflow depths from fluvial deposits in the early Palaeogene Willwood Formation of north‐west Wyoming, USA. Fluvial story heights (n = 60) and mud plug thicknesses (n = 13) are statistically indistinguishable from one another and yield palaeoflow depth estimates of 4 to 6 m. The vertical relief on bar clinoforms (n = 112) yields smaller flow depths, by a factor of ca 0.3, with the exception that the largest bar clinoforms match story heights and mud plug estimates. This observation is consistent with modern river data sets that indicate unit bar clinoforms do not capture the reach‐mean bank‐full flow depths except in rare circumstances. Future studies should use story heights (i.e. compound bar deposits) and mud plugs to estimate bank‐full flow depths in alluvial strata. Additionally, the thickness of multi‐storied fluvial sandbodies (n = 102) and overbank cycles composed of paired crevasse splay and palaeosol deposits (n = 45) were compared. The two depositional units display statistically indistinguishable mean and median values. Building upon previous depositional models, these observations suggest basin rivers aggraded approximately one flow depth prior to major avulsion. This avulsion process generated widespread crevasse splay deposition across the floodplain. Once the main river channel stem was reestablished, overbank flooding and palaeosol development dominated floodplain settings. The depositional model implies river aggradation autogenically generated topography in the basin that was effectively filled during the subsequent avulsion. This constitutes a meso‐timescale (103–104 years) compensational pattern driven by morphodynamics that may account for the high completeness of fossil and palaeoclimate records recovered from the basin.

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Section: Discussionmentioning

confidence: 99%

Flow depth estimates and avulsion behaviour in alluvial stratigraphy (Willwood Formation, Bighorn Basin, Wyoming, USA)

Foreman,

Sutherland,

Todd

et al. 2023

The Depositional Record

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“…The provenance of the Colorado has been unchanged for about 2.5 Ma, so the tectonic evolution of the catchment cannot be a factor: the sediment source has remained the Colorado Plateau throughout this period [8]; this is supported by the compilation and modelling work of Fernandes et al [68], which shows that the Colorado Plateau has been elevated since the Paleocene. However, in their study of the Sylhet River, Sincavage et al [76] pointed out that there is a distinction between tectonic scale (10 2 km) and event scale (10 1 km) processes; they demonstrated that although tectonics created steeper and more favourable pathways into the receiving basin, the Sylhet continued to occupy a longer and less steep existing channel which had been enhanced by large flood events. Their dictum that large-scale stochastic events should have equal weight to tectonic and climatic events-in the case of the Sylhet, in the creation of pre-existing topography-is clearly applicable to the Olla Formation.…”

Section: Provenance Mixing-controls and Processesmentioning

confidence: 99%

Defining Regional and Local Sediment Sources in the Ancestral Colorado River System: A Heavy Mineral Study of a Mixed Provenance Unit in the Fish Creek-Vallecito Basin, Southern California

McGill¹,

Nicholson

Frei

et al. 2023

Geosciences

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The Colorado River has flowed across the dextral strike-slip plate boundary between the North American and Pacific plates since the latest Miocene or earliest Pliocene. The Fish Creek-Vallecito Basin (FCVB) lies on the Pacific Plate in southern California, dextrally offset from the point where the modern Colorado river enters the Salton Trough; it contains a record of ancestral Colorado River sedimentation from 5.3–2.5 Ma. The basin stratigraphy exhibits a changing balance between locally derived (L-Suite) and Colorado River (C-Suite) sediments. This paper focuses on the Palm Springs Group (PSG), a thick fluvial and alluvial sequence deposited on the upper delta plain (between 4.2–2.5 Ma) when the Colorado was active in the area, allowing the detailed examination of the processes of sediment mixing from two distinct provenance areas. The PSG consists of three coeval formations: 1) Canebrake Conglomerate, a basin margin that has coarse alluvial fan deposits derived from surrounding igneous basement; 2) Olla Formation, fan-fringe sandstones containing L-Suite, C-Suite, and mixed units; and 3) Arroyo Diablo Formation, mineralogically mature C-Suite sandstones. Stratigraphic analysis demonstrates that the river flowed through a landscape with relief up to 2000 m. Satellite mapping and detailed logging reveal a variable balance between the two suites in the Olla Formation with an apparent upward increase in L-Suite units before abrupt cessation of Colorado sedimentation in the basin. Stable heavy mineral indices differentiate L-Suite (high rutile:zircon index: RZi 40–95) from C-Suite (RZi: 0–20). Both suites have garnet:zircon index (GZi) and apatite:tourmaline index (ATi) mostly above 50, although many L-suite and mixed Olla samples have much lower ATi (20–50), suggesting that the distal floodplain was wet and the local sediment had a longer residence time there, or went through several cycles of erosion and redeposition. Heavy mineral analysis, garnet geochemical analysis, and detrital zircon U-Pb age spectra allow us to quantify the amount of mixing from different sediment sources. These data show that about 30% of the mixed units are derived from the Colorado River and that up to 20% of the L-Suite is also derived from the Colorado River, suggesting that there was mutual cannibalisation of older deposits by fluvial channels in a transitional area at the basin margin. Although this study is local in scope, it provides an insight into the extent and nature of sediment mixing in a two-source system. We conclude that most ‘mixing’ is actually interbedding from separate sources; true mixing is facilitated by low subsidence rates and the rapid migration of fluvial channels.

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Antecedent Topography and Sediment Dispersal: The Influence of Geologically Instantaneous Events on Basin Fill Patterns

Abstract: River avulsions, broadly defined as the abandonment of an active channel and the formation or occupation of a new channel, play a critical role in delta sediment dispersal and landscape evolution in fluvially dominated systems.

Cited by 2 publications

References 96 publications

Flow depth estimates and avulsion behaviour in alluvial stratigraphy (Willwood Formation, Bighorn Basin, Wyoming, USA)

Flow depth estimates and avulsion behaviour in alluvial stratigraphy (Willwood Formation, Bighorn Basin, Wyoming, USA)

Defining Regional and Local Sediment Sources in the Ancestral Colorado River System: A Heavy Mineral Study of a Mixed Provenance Unit in the Fish Creek-Vallecito Basin, Southern California

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