ABSTRACT
The sand dunes that extend between Al Ain and Abu Dhabi in belt some 120 km long and 20 km wide were studied from geomorphological and sedimentological point of view. One hundred and thirty samples were collected and analyzed using conventional sieving methods, scanning electron microscopy, and X-ray diffraction. These sediments are classified as fine sand moderately well sorted, near symmetrical, and mesokurtic. Sands from the crests of the dunes are generally coarser and less well sorted than those from the remaining portions of the dunes. The leeward slopes are finer and better sorted than the stossward slopes. The grains are subrounded and poorly sorted. The relatively high degree of roundness may be attributed to the sands being recycled aeolian sand grains. An increase in grain roundness is associated with increase in grain size of the sands, while increasing sorting was associated with a decrease in grain size and roundness of the sands. Mechanical and chemical (dissolution) features affect the surface features of the quartz grains. The mechanical features include upturned plates, meandering ridges irregular depressions and pits, conchoidal fractures, and polygonal cracks. Chemical features are intensively imprinted on the sand grains, particularly where both dissolution and precipitation have occurred. These features include irregular solution pits, gulling, silica globules, quartz overgrowths, and smoothed surfaces. The huge sand dunes in the UAE are part of a great belt that extends from southern Iraq to northeast Saudi Arabia, formed by the prevailing winds of the last glacial period.
