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The AAPG/Datapages Combined Publications Database

CSPG Special Publications


Fluvial Sedimentology — Memoir 5, 1977
Pages 577-586
Fluvial Facies Models

Vertical Sequence and Sand Body Shape in Alluvial Sequences

J. D. Collinson


The type of channel which deposited coarse member sand bodies in alluvial sequences has largely been deduced from coarse member - fine member ratios, palaeocurrent patterns and the internal organisation of grain size and sedimentary structures. The shape of the sand bodies has seldom been considered an important piece of evidence and has more often been a predictive target. Work on modern rivers shows that no one vertical sequence typifies a particular type of channel but that different channel types generate diverse suites of sequences which give scope for ambiguity in interpretations. For highly sinuous streams, the maximum lateral extent of the sand bodies generated by point bar migration can be predicted by empirical equations. Comparisons of predicted maximum lateral extents with the dimensions of ancient sandstone bodies shows that some sandstones, previously interpreted as of point bar origin, are more likely to be the products of low sinuosity streams or of sheet floods.

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