Sedimentological characteristics and morphology of the aeolian sand dunes in the eastern part of the UAE: a case study from Ar Rub' Al Khali

The Umm Az Zimul-Al Wijan area is located in the southeastern part of the U AE and covers about 1600 km(2). It is bounded to the east by the Oman Mount ains and to the south and west by the extensive dune area of,Ar Rub Al Khal i. Field investigation revealed the common occurrence of parallel to sub-pa rallel sand ridges with a general east-west orientation. Also present, but less frequent, are barchan, barchanoid and star dunes. Interdune areas are classified into four types that include: dolomite, mixed ancient sabkha and ophiolitic rock fragments, mixed sand sheet and ophiolitic rock fragments, and recent sabkha. The textural characteristics of the sand forming the du nes are unimodal with a modal class in fine sand size, moderately to very w ell sorted, positively skewed and mesokurtic. Quartz grains are mainly subr ounded to subangular. The similarity in roundness properties in different d une types in the eastern province of the UAE seems not to be influenced by dune form. Based on the heavy mineral suites and the angularity of quartz g rains, it is believed that the sand sediments are mostly derived from the u ltrabasic rocks forming the ophiolitic sequence of the Oman Mountains, acid ic rocks of Iran and from the coastal area. (C) 1999 Elsevier Science B.V. All rights reserved.