Computer Science
Scientific paper
May 1977
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1977esrv...13....1m&link_type=abstract
Earth Science Reviews, Volume 13, Issue 1, p. 1-62.
Computer Science
150
Scientific paper
Generalized sedimentation models have been developed from a review of more than sixty recent papers on modern and ancient braided-stream deposits. Braided rivers consist of a series of broad, shallow channels and bars, with elevated areas active only during floods, and dry islands. There are three main bar types; longitudinal, comprising crudely bedded gravel sheets; transverse to linguoid, consisting of sand or gravel and formed by downstream avalanche-face progradation; and point or side bars, formed by bedform coalescence and chute and swale development in areas of low energy. Important sediment-forming processes include bar formation, channel-floor dune migration, low-water accretion and overbank sedimentation. Braided-stream deposits consist of up to three gravel facies, five sand facies and two fine-grained facies. Vertical sequences recorded in modern and ancient deposits are of several types: flood-, channel fill-, valley fill-, channel re-occupation- and point bar-cycles. Some of these fine upward and could be confused with meandering-river sequences. Facies assemblages and vertical sequences fall into four main classes, which are proposed as sedimentation models for the interpretation of ancient braided-river deposits in the surface and subsurface:Scott type: consists mainly of longitudinal bar gravels with sand lenses formed by infill of channels and scour hollows during low water.Donjek type: may be dominated by sand or gravel; distinguished by fining-upward cycles caused by lateral point-bar accretion or vertical channel aggradation. Cycles commonly are less than 3 m thick, but cycles up to 60 m may be present, representing valley-fill sequences. Longitudinal and linguoid-bar deposits, channel-floor dune deposits, bar-top and overbank deposits all may be important.Platte type: characterized by an abundance of linguoid bar and dune deposits (planar and trough crossbedding). No well-developed cyclicity, probably owing to a lack of topographic differentiation in the river (no evidence of deep, primary channels, abandoned areas or overbank areas). (4) Bijou Creek type: consists of horizontally laminated sand plus subordinate amounts of sand showing planar crossbedding and ripple marks. Formed during flash floods and may be most typical of ephemeral streams.
No associations
LandOfFree
A review of the braided-river depositional environment does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A review of the braided-river depositional environment, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A review of the braided-river depositional environment will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1882966