Page 61 - Sedimentology and Stratigraphy

Processes of Transport and Sedimentary Structures
48 Nichols/Sedimentology and Stratigraphy 9781405193795_4_004 Final Proof page 48 26.2.2009 8:16pm Compositor Name: ARaju

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Fig. 4.4 The lift force resulting from the
Bernoulli effect causes grains to be
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Fig. 4.5 The Hju ¨lstrom diagram shows the relationship between the velocity of a water flow and the transport of loose grains.
Once a grain has settled it requires more energy to start it moving than a grain that is already in motion. The cohesive
properties of clay particles mean that fine-grained sediments require relatively high velocities to re-erode them once they are
deposited, especially once they are compacted. (From Press & Siever 1986.)