Abstract

A coarse-grained sequence of turbidite-conglomerates at Wheeler Gorge, California, was deposited by a series of high-density, highly fluid underwater flows into deep water. Inverse grading is developed at the base of each conglomerate unit within the sequence, and one unit forcibly intruded shales to form graded sills. Reverse grading may in part be explained by Bernoulli's principle whereby pressures near the boundary of deposition tend to drive the large particles upward. The 'Bernoulli boundary layer effect' may explain reverse grading in coarse-grained turbidite deposits, in mudflows, possible ignimbrite layers, and in igneous intrusions of the 'Muskox type' which have boundaries that are finer grained than their interior parts.

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