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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. 60.  Zig-zag structure formed by a dune with reversing lee-side spurs and scour pits; Lamb Point Tongue (Upper Triassic?) of the Navajo Sandstone, Kanab Creek, Utah.

RECOGNITION: The back-and-forth migration of the topographic features that deposited this structure is clearly exhibited by the zig-zagging cross-beds and bounding surfaces.  Measurements of cross-bed and bounding-surface attitudes showed that the cross-beds dip with a component toward the viewer, the same general dip direction as in simple cross-beds in the area (Hunter and Rubin, 1983).  Thus, the spur and scour pits that deposited this structure reversed back and forth across the outcrop plane while migrating toward the viewer; this depositional situation is simulated in Figure 59.

 

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