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ABSTRACT

A ground-penetrating radar survey of aeolian dunes in the Al Liwa area of Abu Dhabi reveals a variety of dipping reflectors which are interpreted as primary sedimentary structures. The interpretation of the radar profiles has been confirmed by bulldozing trenches through the study area and comparing logged sections in the trenches with the radar profiles. NNW— SSE-orientated radar profiles, approximately parallel to the prevailing wind direction, show two sets of dipping reflectors which are interpreted as sets of cross-stratification and second- and third-order bounding surfaces. Radar profiles orientated WSW—ENE across the prevailing wind direction are dominated by concave-up reflectors which are interpreted as trough-shaped scours and sets of trough cross-stratification produced by oblique progradation of barchanoid dunes. Nested troughs, with small sets of trough cross-stratification within larger troughs, may be due to reactivation following wind reversal, or the superposition of small dunes on larger dunes and the fill of large dune troughs by smaller dunes. Convex-upwards reflectors are interpreted as linear spurs on the convex portions of sinuous dunes or erosional remnants between troughs. Overall there is a tendency for the larger second-order bounding surfaces to dip downwind, which confirms Brookfield's ideas of the relative migration paths of dunes and draa.