Other Dunes and Other Sand Deposits - Dune Worlds: How Windblown Sand Shapes Planetary Landscapes - page 94

7.10 Compound Dunes and Complex Dunes

Compound forms consist of two or more of the basic dune
types formed by some combination of sand supply and wind
regime changes, resulting in the close association of two
distinct scales of dune forms. Examples of common com-
pound dunes include coalescing barchanoid ridges, coa-
lescing star dunes, small barchans on the flanks of large
barchans, small parabolic dunes between the arms of a large
parabolic dune, and large sand ridges superposed by smaller
linear dunes. Successive generations of bedform are seen
particularly on linear dunes (which may in general be older
than other types), for example, Figs. 7.11 and 7.12 .
Ewing and Kocurek (2010) (see Chap. 19 ) have devel-
oped 'pattern analysis' approaches to disentangle successive
generations of superposed dunes, identifying, e.g., three
generations in the Namib. The computational approaches
described in Chap. 19 offer promise that it may be possible
to quantitatively relate such superposed duneforms to a
wind regime history.
It is common to see small duneforms develop somewhat
transversal to the orientation of large linear dunes. These
may result from flow along the linear forced by the presence

Fig. 7.12 A similar superposition is seen in Oman in this SPOT
image. Here the superposed smaller dunes are much more extensive
and almost hide the larger underlying uruq pattern beneath at the
bottom of the image

Fig. 7.13 Linear dune in the
Rub' Al Khali in eastern United
Arab Emirates, with regular
transverse ridges developing
along its flank. Photo J.
Radebaugh