Pacific Coastal and Marine Science Center
Bedform Sedimentology Site: “Bedforms and Cross-Bedding in Animation”
FIG. 65. Structure formed by two-dimensional bedforms with downslope-migrating superimposed bedforms with sinuous, out-of- phase crestlines. Similar structures have been reported from ancient marine deposits by Anastas et al. (1997, fig. 11a).
RECOGNITION: This structure is superficially similar to the structure produced by sinuous out-of-phase bedforms migrating across a horizontal surface (Fig. 34), but two obvious differences arise from the downslope migration of the superimposed bedforms. First, sets of cross-beds deposited by the superimposed bedforms are grouped in larger sets deposited by the main bedforms. Second, downslope migration of the superimposed bedforms causes the bounding surfaces that they scour to dip downcurrent.
ORIGIN: This example is similar to that in Figure 25, but the superimposed bedforms in the example shown here are three- dimensional.