INTERNAL STRUCTURE OF AEOLIAN DUNES IN ABU-DHABI DETERMINED USING GROUND-PENETRATING RADAR

A ground-penetrating radar survey of aeolian dunes in the Al Liwa area of Abu Dhabi reveals a variety of dipping reflectors which are interp reted as primary sedimentary structures. The interpretation of the rad ar profiles has been confirmed by bulldozing trenches through the stud y area and comparing logged sections in the trenches with the radar pr ofiles. NNW- SSE-orientated radar profiles, approximately parallel to the prevailing wind direction, show two sets of dipping reflectors whi ch are interpreted as sets of cross-stratification and second- and thi rd-order bounding surfaces. Radar profiles orientated WSW-ENE across t he prevailing wind direction are dominated by concave-up reflectors wh ich are interpreted as trough-shaped scours and sets of trough cross-s tratification produced by oblique progradation of barchanoid dunes. Ne sted troughs, with small sets of trough cross-stratification within la rger troughs, may be due to reactivation following wind reversal, or t he superposition of small dunes on larger dunes and the fill of large dune troughs by smaller dunes. Convex-upwards reflectors are interpret ed as linear spurs on the convex portions of sinuous dunes or erosiona l remnants between troughs. Overall there is a tendency for the larger second-order bounding surfaces to dip downwind, which confirms Brookf ield's ideas of the relative migration paths of dunes and draa.