Pacific Coastal & Marine Science Center
Bedform Sedimentology Site: “Bedforms and Cross-Bedding in Animation”
FIG. 62. Zig-zag structure deposited by dune with reversing lee-side spurs and scour pits; Navajo Sandstone (Upper Triassic? and Jurassic) near Escalante, Utah.
RECOGNITION: The set of cross-beds in the center of this photograph was deposited by a dune that migrated into the plane of the outcrop. While the dune was migrating, lee-side spurs and scour pits reversed migration direction or asymmetry, thereby creating the zig-zagging sets of cross-beds. Numbers identify the sequence in which specific sets were deposited. Note the alternating dip directions (sets 1 and 3 dip to the left in the outcrop plane; sets 2 and 4 dip to the right). The set of zig-zags is approximately 10 m thick.