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Journal ArticleDOI

Sedimentology and Bar Formation in the Upper Kicking Horse River, a Braided Outwash Stream

01 Mar 1974-The Journal of Geology (University of Chicago Press)-Vol. 82, Iss: 2, pp 205-223
TL;DR: Bar formation and sediment distribution patterns were examined in a 4-mile braided reach of the upper Kicking Horse River at Field, British Columbia, which was mainly supplied by meltwater from icefields straddling the continental divide at the British Columbia-Alberta boundary in the southeastern Canadian Cordillera as mentioned in this paper.
Abstract: Bar formation and sediment distribution patterns were examined in a 4-mile braided reach of the upper Kicking Horse River at Field, British Columbia, which is mainly supplied by meltwater from icefields straddling the continental divide at the British Columbia-Alberta boundary in the southeastern Canadian Cordillera. Marked diurnal variations in discharge, suspended sediment concentration, and water temperature occur during peak summer melting periods when rates of sediment transport and bar formation are greatest. Bed material is mostly limestone and dolomite gravel which undergoes rapid fining in the downstream direction. Gravel bars occurring in a wide variety of shapes and sizes comprise the dominant bed forms. Most exposed braid bars have undergone complex depositional and erosional histories and rarely show simple or consistent patterns of grain size or structures, either internal or superficial. Active bars with simple histories and predominantly depositional morphologies are termed "unit bars." Fo...
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors proposed a new method of analysis for fluvial facies, which subdivides fluvic deposits into local suites consisting of one or more of a set of eight basic three-dimensional architectural elements.

1,804 citations

Journal ArticleDOI
TL;DR: A review of more than sixty recent papers on modern and ancient braided-stream deposits can be found in this article, where several sedimentation models have been developed from a review of recent work.

1,755 citations

Journal ArticleDOI
TL;DR: A Symposium entitled "Classification of Large-Scale Flow-Transverse Bedforms" was convened at the 1987 Mid-Year Meeting of SEPM in Austin, Texas with the purpose of examining the problems involved in classifying large subaqueous flow-transverse bedforms developed in fluvial, intertidal, and marine environments, and recommending changes in nomenclature.
Abstract: A Symposium entitled "Classification of Large-Scale Flow-Transverse Bedforms" was convened at the 1987 Mid-Year Meeting of SEPM in Austin, Texas with the purpose of examining the problems involved in classifying large subaqueous flow-transverse bedforms developed in fluvial, intertidal, and marine environments, and recommending changes in nomenclature. The consensus of the participants is that despite the wide spectrum of morphologies of large-scale flow-transverse bedforms (excluding antidunes), they all occupy a similar position in the lower-flow-regime sequence between ripples and upper plane bed. The wide variety of forms is a reflection of secondary effects such as channelization, fluctuating water levels, and unsteady and reversing flows. The bedforms appear not to fall into size classes with naturally occurring boundaries but rather form a continuum with spacing from just under 1 m to over 1,000 m. The symposium panel proposes, therefore, that they should have only one name, DUNE. Dune is preferred as it has historical precedence over other terms in use, such as megaripple and sand wave. The term "dune" should be modified by primary descriptors of shape (i.e., 2-D or 3-D) and size based on spacing (small (0.6-5 m), medium (5-10 m), large (10-100 m) or very large (> 100 m) and the adjective subaqueous when it is important to distinguish them from eolian dunes. The panel recommends a morphologically based classification that is descriptive, with an underlying genetic rationale. Second order descriptors such a sediment size and bedform superposition may be used to describe more thoroughly the variety of subaqueous dunes in nature.

1,022 citations

Journal ArticleDOI
TL;DR: The fine to very coarse sandstones, gravelly sandstones and intraformational conglomerates of the mid to upper Brownstones are excellently exposed in large fresh road cuttings near Ross-on-Wye in the southern Welsh Borders.

549 citations

Journal ArticleDOI
TL;DR: The South Saskatchewan River has a long term average discharge of 275 m3/sec, with flood peaks in the range of 1500 to 3800 m 3/sec as discussed by the authors, and the dominant channel bedforms are dunes, which deposit trough cross bedding.
Abstract: The South Saskatchewan River has a long term average discharge of 275 m3/sec, with flood peaks in the range of 1500 to 3800 m3/sec. South of Saskatoon, the four major types of geomorphological elements recognised are channels, slipface-bounded bars, sand flats and vegetated islands and floodplains. Major channels are 3-5 m deep, up to 200 m wide, and flow around sand flats which are 50-2000 m long, and around vegetated islands up to 1 km long. At areas of flow expansion, long straight-crested cross-channel bars form. During falling stage, a small part of the crest of the cross-channel bar may become emergent, and act as a nucleus for downstream and lateral growth of a new sand flat. The dominant channel bedforms are dunes, which deposit trough cross bedding. Cross-channel bars deposit large sets of planar tabular cross bedding. Sand flats that grow from a nucleus on a cross-channel bar are mostly composed of smaller planar tabular sets, with some parallel lamination, trough cross-bedding, and ripple cross-lamination. A typical facies sequence related to sand flat growth would consist of in-channel trough cross-bedding, overlain by a large (1-2 m) planar tabular set (cross-channel bar), overlain in turn by a complex association mostly of small planar tabular cross-beds, trough cross-beds and ripple cross-lamination. By contrast, a second stratigraphic sequence can be proposed, related only to channel aggradation. It would consist dominantly of trough cross-beds, decreasing in scale upward, and possible interrupted by isolated sets of planar tabular cross-bedding if a cross-channel bar formed, but failed to grow into a sand flat. During final filling of the channel, ripple cross-lamination and thin clay layers may be deposited. In the S. Saskatchewan, these sequences are a minimum of 5 m thick, and are overlain by 0.5-1 m of silty and muddy vertical accretion deposits.

535 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a bar on the Brazos River near Calvert, Texas, has been analyzed in order to determine the geologic meaning of certain grain size parameters and to study the behavior of the size fractions with transport.
Abstract: A bar on the Brazos River near Calvert, Texas, has been analyzed in order to determine the geologic meaning of certain grain size parameters and to study the behavior of the size fractions with transport. The bar consists of a strongly bimodal mixture of pebble gravel and medium to fine sand; there is a lack of material in the range of 0.5 to 2 mm, because the source does not supply particles of this size. The size distributions of the two modes, which were established in the parent deposits, are nearly invariant over the bar because the present environment of deposition only affects the relative proportions of the two modes, not the grain size properties of the modes themselves. Two proportions are most common; the sediment either contains no gravel or else contains about 60% gravel. Three sediment types with characteristic bedding features occur on the bar in constant stratigraphic order, with the coarsest at the base. Statistical analysis of the data is based on a series of grain size parameters modified from those of Inman (1952) to provide a more detailed coverage of non-normal size curves. Unimodal sediments have nearly normal curves as defined by their skewness and kurtosis. Non-normal kurtosis and skewness values are held to be the identifying characteristics of bimodal sediments even where such modes are not evident in frequency curves. The relative proportions of each mode define a systematic series of changes in numerical properties; mean size, standard deviation and skewness are shown to be linked in a helical trend, which is believed to be applicable to many other sedimentary suites. The equations of the helix may be characteristic of certain environments. Kurtosis values show rhythmic pulsations along the helix and are diagnostic of two-generation sediments.

6,310 citations

Journal ArticleDOI
TL;DR: In this article, a straight, four-mile tract of the Donjek River, Yukon, Canada is braided throughout, discharging about 50,000 cfs in flood.
Abstract: A straight, four-mile tract of the Donjek River, Yukon, Canada is braided throughout, discharging about 50,000 cfs in flood. The active part of the tract shows upper regime flow in the main channels, and lacks vegetation. Higher, older levels are former river courses, partly or completely vegetated, with continuous flow (principally lower regime) only in the main channels. Comparing channel (width:depth) and topographic indices, the younger surfaces are more strongly dissected because of active channel cutting, whereas channels on older levels are subject to infilling. The sediments vary from clays to coarse gravels; most are poorly sorted. CM plots permit division into three main groups: silt and mud of low energy environments such as abandoned channels, gravel of high energy channel-bar complexes, and a variable intermediate group which fills channels under medium-energy conditions. Seven facies are distinguished on textural, floral, and sedimentary structural characteristics. Facies relations are mostly gradational within channels, commonly fining upwards. They are more complex between channels, and invariably erosional. The origin and directional significance of hierarchical orders of sedimentary structures were studied. Six hundred and sixty measurements of small-scale structures (mostly ripples) show moderate within-bar and between-bar variation, and give a grand vector mean 22 degrees from the river trend. Bisectors of channel directional arcs (maximum and average ranges) approximate the river trend within 5 degrees.

378 citations

Journal ArticleDOI
TL;DR: In this paper, relative abundances of planar cross-stratification and horizontal stratification, as well as bed-relief indices were measured in sandstones and conglomerates of the Lower Silurian Shawangunk Conglomerate, Green Pond Conglerate, and Tuscarora Sandstone in New Jersey and Pennsylvania.
Abstract: Studies of the South Platte-Platte River in Colorado and Nebraska substantiate Ore9s (1964) conclusion that braided patterns in streams are created mainly by accretion of longitudinal bars and dissection of transverse bars. Distribution of bars in the South Platte-Platte River depends on texture of the bed load. Coarse, poorly sorted sediment favors formation of longitudinal bars, and finer grained, better sorted materials form transverse bars. The relative proportion of transverse to longitudinal bars increases downstream, following the river9s tendency to fractionate its load into finer sizes downstream. This is accompanied by an increase in the ratio of planar cross-stratification to horizontal stratification and a decrease in cross-channel topographic relief expressed as a bed-relief index. Relative abundances of planar cross-stratification and horizontal stratification, as well as bed-relief indices were measured in sandstones and conglomerates of the Lower Silurian Shawangunk Conglomerate, Green Pond Conglomerate, and Tuscarora Sandstone in New Jersey and Pennsylvania. These formations display downslope trends similar to those of the South Platte and Platte Rivers, and, combined with paleocurrent, grain-size distribution, and other data, suggest that the coarse eastern facies (Green Pond, Shawangunk) represent proximal braided stream deposits with longitudinal bars that grade westward and northwestward into finer grained distal braided stream sediments (Tuscarora) characterized by transverse bars.

309 citations

Journal ArticleDOI
TL;DR: The greater part of the water and sediment discharge in the Tana River takes place in the weeks following the ice break-up and flood, and during this time the river discharge changes rapidly with an ov...
Abstract: The greater part of the water and sediment discharge in the Tana River takes place in the weeks following the ice break-up and flood. During this time the river discharge changes rapidly with an ov...

240 citations