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Pacific Coastal & Marine Science Center

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

Cross-Bedding, Bedforms, and Paleocurrents

Dip plots, static images, and captions

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Dip plot; see caption below.
Static image of cross-section; see caption below.

FIG. 42b.  Structures formed by bedforms with along-crest- migrating in-phase sinuosities.  Fig. 42a (A) Rate of along-crest migration of sinuosities is equal to the rate of lateral migration of the main bedform.  Fig. 42b (B) Rate of along-crest migration of sinuosities is approximately four times the rate of lateral migration of the main bedform.

RECOGNITION: These structures are most easily recognized in horizontal sections, because such sections display both the lateral migration of the bedforms and the along-crest displacement of the crestline sinuosities.  Like other structures deposited by oblique bedforms, this structure has dip patterns in which cross-beds and bounding surfaces are asymmetrically distributed relative to the center of the plot and relative to each other.  Note the divergence between the trough axes and the cross-bed dip directions.

ORIGIN: Deposition of these structures requires sinuous bedforms that are oblique to the resultant transport direction.  An example of real bedforms with along-crest-migrating sinuosities is shown in Figure 70.

 

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