Deposits of Sand: Ripples Versus Dunes - Dune Worlds: How Windblown Sand Shapes Planetary Landscapes - page 64

Fig. 5.21 Exposed layers in the damp sand of Lencois Maranhenses
(a lagoon is just visible at top left) showing the arcuate former
positions of the slipface of the barchanoid dunes. Jani Radebaugh for

scale. Some wavy elemental dunes are forming in the background as
the bright sand starts to dry and organize. Photo R. Lorenz

Fig. 5.22 Simulations of bed formation by Dave Rubin of the USGS
show that the bedding pattern contains rich information that maps to
the sequence of deposition styles. In this example, dunes form layers
with additional complexity from along-crest migrating superimposed

bedforms. The bedforms have a height ratio of 0.45 and a speed ratio
of 0.3. The resulting ratio of along- to across-crest transport is 0.135;
the transport direction is oriented 82 from the crestline of the main
bedforms. Image USGS