Revision of Platte River Alluvial Facies Model Through Observations of Extant Channels and Barforms, and Subsurface Alluvial Valley Fills

Horn, John Daniel; Fielding, Christopher R.; Joeckel, R.M.

doi:10.2110/jsr.2012.9

Cited by 49 publications

(51 citation statements)

References 18 publications

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“…Deeper channel belts probably hosted a more complex depositional topography (Straub et al 2009;Ielpi and Ghinassi 2015), which would have induced local paleoflow dispersion (Shukla et al 1999). Direct comparison between channel flows at sites II and III are consistent with multiple fluvial trunks, indicating either frequent avulsion or coalescence of large, compound mid-channel bars into islands (Joeckel and Henebry 2008;Horn et al 2012). As shallow, braided-channel belts were active in valley-confined settings, avulsion processes appear less likely, or restricted to local phenomena (Heller and Paola 1996).…”

Section: Channel-belt Planview Stylementioning

confidence: 96%

Highly Variable Precambrian Fluvial Style Recorded In the Nelson Head Formation of Brock Inlier (Northwest Territories, Canada)

Ielpi

Rainbird

2016

Journal of Sedimentary Research

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Spectacular canyon exposures of the~1 Ga Nelson Head Formation along the modern Brock River, Northwest Territories, provide a rare opportunity to assess the deposits of pre-vegetation, braided to sinuouschannelized fluvial systems. We analyze the sedimentology, architecture, and depositional evolution of 16 stacked fluvial-channel belts at this site, demonstrating greater variability in sedimentary style and morphodynamics than is typically interpreted for Precambrian rivers. Inferences on fluvial planview based on integrated analysis of depositional architecture and paleoflow reveal complex patterns of channel-planform evolution, and four depositional stages are recognized: (1) floodbasin-splay progradation with bounding episodes of eolian reworking; (2) deposition in wandering-channel belts characterized by deep anabranches and prominent lateral accretion; (3) progressive shift towards shallow, braided-channel belts confined within alluvial valleys and dominated by downstream accretion; and (4) deposition by marine-influenced braided-channel belts with mixed downstream, lateral, and upstream accretion.Overall, the studied fluvial-channel belts point to significant morphodynamic complexity and geomorphic variability, challenging the assumption that all pre-Silurian rivers shared poor channelization and low sinuosity. Observed channel bodies also have width:thickness ratios strongly overlapping with those of rivers postdating the rise of vegetation. In both wandering-and braided-channel belts, complex patterns of channel migration, bar accretion, and dissection were the result of co-acting processes such as development of transverse-velocity zones within the channels, local paleoflow disturbance induced by depositional topography, and avulsion. In concert with the regional extent and paleoflow, and increasingly distal character of correlative stratigraphic units towards the northwest, the magnitude of the observed trunk-fluvial channels is consistent with a mature drainage capable of transecting the Laurentian craton over thousands of kilometers.

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Section: Channel-belt Planview Stylementioning

confidence: 96%

Highly Variable Precambrian Fluvial Style Recorded In the Nelson Head Formation of Brock Inlier (Northwest Territories, Canada)

Ielpi

Rainbird

2016

Journal of Sedimentary Research

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“…6). Considerable variability in sedimentary architecture is known to exist between bars in the same reach (Sambrook Smith et al, 2006;Lane et al, 2008;Ashworth et al, 2011;Horn et al, 2012;Reesink et al, 2014aReesink et al, , 2014b. Variability in locally enhanced dune preservation is tied to this variability in bar morphology, such that a deposit of a few hundred meters in width or length may not be an adequate representation of the behavior of the entire river reach.…”

Section: Ways Forward In the Analysis Of Subaqueous Dune Preservationmentioning

confidence: 99%

Extremes in dune preservation: Controls on the completeness of fluvial deposits

Reesink

Berg

Parsons

et al. 2015

Earth-Science Reviews

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Understanding sedimentary preservation underpins our ability to interpret the ancient sedimentary record and reconstruct paleoenvironments and paleoclimates. Dune sets are ubiquitous in preserved river deposits and are typically interpreted based on a model that describes the recurrence of erosion in a vertical sequence, but without considering spatial variability. However, spatial variability in flow and sediment transport will change the recurrence of erosion, and therefore dune preservation. In order to better understand the limits of these interpretations and outline the causes of potential variability in preservation potential, this paper reviews existing work and presents new observations of an extreme end-member of dune preservation: 'form-sets', formed by dunes in which both stoss-and lee-slopes are preserved intact. These form-sets do not conform to models that are based on the recurrence of erosion, since erosion does not recur in their case, and can therefore be used to evaluate the assumptions that underpin sedimentary preservation. New Ground Penetrating Radar data from the Río Paraná, Argentina, show dune fields that are buried intact within larger scale barforms. These trains of form-sets are up to 300 m in length, are restricted to unit-bar troughs in the upper 5 m of the channel deposits, occur in N 5% of the mid-channel bar deposits, show reactivation surfaces, occur in multiple levels, and match the size of average-flow dunes. A review of published accounts of form-sets highlights a diversity of processes that can be envisaged for their formation: i) abandonment after extreme floods, ii) slow burial of abandoned dune forms by cohesive clay in sheltered bar troughs and meander-neck cut-offs, iii) fast burial by mass-movement processes, and iv) climbing of dune sets due to local dominance of deposition over dune migration. Analysis of these new and published accounts of form-sets and their burial processes highlights that form-sets need not be indicative of extreme floods. Instead, form-sets are closely associated with surrounding geomorphology such as river banks, meander-neck cut-offs, and bars because this larger-scale context controls the local sediment budget and the nature of recurrence of erosion. Locally enhanced preservation by the 'extreme' dominance of deposition is further promoted by finer grain sizes and prolonged changes in flow stage. Such conditions are characteristic, although not exclusive, of large lowland rivers such as the Río Paraná. The spatial control on dune preservation is critical: although at-a-point models adequately describe near-horizontal sets of freely migrating dunes in uniform flows, they are unsuitable for inclined dune co-sets and other cases where multiple scales of bedforms interact. Spatial and temporal variations in flow and sediment transport between the thalweg and different positions on larger bar-forms can change the preservation potential of dunes within river channels. Therefore, dune set thickness distributions are likely grouped in larger-scale un...

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“…Given the profound influence of woody plant debris, Ielpi et al interpreted the multistorey channel bodies as the deposits of anabranching, island-braided sandbed rivers, with morphodynamics similar to those described for the modern Platte River (Horn et al 2012), the Tagliamento River and other island-braided, wandering, or sandy anabranching systems (Gurnell et al 2001, Tockner et al 2003.…”

Section: Ward Point Member Channel Bodiesmentioning

confidence: 99%

Sedimentology and stratigraphy of the type section of the Pennsylvanian Boss Point Formation, Joggins Fossil Cliffs, Nova Scotia, Canada

Rygel

Lally

Gibling

et al. 2015

atgeol

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The 1125-m-thick type section of the Pennsylvanian Boss Point Formation is well exposed along the shore of the Bay of Fundy in Nova Scotia. We provide the first comprehensive account of the entirety of this formation, which comprises nearly one-third of the stratigraphic thickness of the Joggins Fossil Cliffs UNESCO World Heritage Site. The basal Chignecto Bay Member (0-91.5 m) is composed of redbeds, single-storey channel bodies with northerly paleoflow, and thin palustrine limestones. The middle Ward Point Member (91.5-951.7 m) contains up to 16 megacycles composed of alternations between thick packages of braided fluvial sandstone and fine-grained deposits. Although regional studies of the Boss Point Formation suggest that the fine-grained deposits are largely composed of lacustrine sediments, these intervals consist largely of poorly drained and well-drained floodplain deposits in the type section. The facies variations and southeast-directed paleoflow in the Ward Point Member record modest uplift associated with the growth of the salt-cored Minudie Anticline. The North Reef Member (951.7-1125 m) is composed of redbeds and two distinctive multistorey channel bodies. This uppermost member records a shift to more arid, oxidizing conditions, was the precursor to a major phase of salt withdrawal, and represents a transition to the overlying Little River Formation. The sedimentological framework, revised stratigraphy, and detailed measured section and map will provide a foundation for future study of this remarkable Pennsylvanian exposure.

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Revision of Platte River Alluvial Facies Model Through Observations of Extant Channels and Barforms, and Subsurface Alluvial Valley Fills

Cited by 49 publications

References 18 publications

Highly Variable Precambrian Fluvial Style Recorded In the Nelson Head Formation of Brock Inlier (Northwest Territories, Canada)

Highly Variable Precambrian Fluvial Style Recorded In the Nelson Head Formation of Brock Inlier (Northwest Territories, Canada)

Extremes in dune preservation: Controls on the completeness of fluvial deposits

Sedimentology and stratigraphy of the type section of the Pennsylvanian Boss Point Formation, Joggins Fossil Cliffs, Nova Scotia, Canada

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