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Pacific Coastal & Marine Science Center

Bedform Sedimentology Site: “Bedforms and Cross-Bedding in Animation”

Cross-Bedding, Bedforms, and Paleocurrents

Photographs

Photo of rock or sand showing pertinent structure or structures; see caption below.

FIG. 52b.  Structures formed by a large dune with along-crest-migrating superimposed dunes; eolian deposits in the Entrada Sandstone (Jurassic) near Page, Arizona.  This is a vertical section, and Figure 52a shows a horizontal section.

RECOGNITION: In this vertical section, the main dune that deposited the entire coset migrated from right to left and toward the viewer. The superimposed dunes migrated into the outcrop, along the lee slope of the main dune.  The structure appears to vary from one place to another on the outcrop, but the differences in appearance are due to outcrop curvature rather than real differences in the structure. At the upper right, the outcrop surface strikes in the same direction as the trend of the superimposed bedforms. Consequently, the cross-bed traces on that part of the outcrop surface parallel the bounding-surface traces, and the cross-bedding appears simple rather than compound (Fig. 46).

 

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