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The Liwa area is located in the south–central part of the UAE along the northeastern upwind margin of the Ar Rub' Al Khali sand sea and covers about 3694 km 2 . It has one type of dunes: a mega-barchan that is compound and complex in form characterized by the superimposition of smaller dunes. Due to the giant size of barchans, interdune areas appear as closed depressions that vary in shape from irregular, elongate, triangular, to circular or semi-circular. These depressions are mostly covered with small barchans or sabkha deposits with patches of gypcrete in their upper parts. Scattered flat-top mounds are also observed in interdune areas. The size of dunes in Liwa is directly controlled by Quaternary climatic changes: multiple generations are superimposed on one another separated by calcretic horizons. The climate during dune formation alternated between relatively arid to humid. The dune sands are unimodal with a modal class of fine sand, moderately to very well sorted, and near symmetrical and mesokurtic. Quartz grains are mainly subrounded to subangular. Based on the heavy-mineral suites, the sand came mostly from the ultrabasic rocks that form the ophiolitic sequence of the Oman Mountains, the acidic rocks of Iran, and from the Arabian Shield.

The Umm Az Zimul–Al Wijan area is located in the southeastern part of the UAE and covers about 1600 km 2 . It is bounded to the east by the Oman Mountains and to the south and west by the extensive dune area of Ar Rub' Al Khali. Field investigation revealed the common occurrence of parallel to sub-parallel 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 dunes are unimodal with a modal class in fine sand size, moderately to very well sorted, positively skewed and mesokurtic. Quartz grains are mainly subrounded to subangular. The similarity in roundness properties in different dune 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 grains, it is believed that the sand sediments are mostly derived from the ultrabasic rocks forming the ophiolitic sequence of the Oman Mountains, acidic rocks of Iran and from the coastal area.

Near-surface sediments in southern Kuwait show extensive development of duricrusts. The host materials are siliciclastic sandstones of the post-Eocene Kuwait Group. Inland, the duricrusts are dominantly pedogenic calcrete (with some silcrete and gypcrete), whereas within 10–20 km of the coast, dolomite is the dominant duricrust mineral. Both these dolocretes and the inland calcretes display a similar maturation sequence in which carbonate-rich nodules develop and coalesce, carbonate progressively replacing and displacing detrital grains. The dolomite of the dolocretes forms mosaics of crystals typically 10–70 μm in size, varying from simple rhombs to spherulites. An intermediate morphology, named artichoke dolomite from its appearance in SEM, is particularly abundant. Authigenic palygorskite is associated with the dolomite. Dissolution of cores or zones within dolomite crystals has occurred. Calcite is present as sparry crystals (always post-dating dolomite) and is the expected precipitate from present-day soil and groundwaters. Chemical analyses of dolomite show highly negative values of δ 13 C (− to − 10.7‰ PDB) and δ 18 O varying from + 0.6 to + 3.3‰ PDB. The oxygen isotope values are interpreted as reflecting evaporation of a marine-based fluid. Manganese values of around 1000 ppm show that this fluid was reducing. Strontium data show variability reflecting mineral-fluid reactions. The general absence of metastable carbonates and presence of zoning in dolomite crystals suggests that meteoric dilution of seawater also occurred. Given that the duricrusts lack biogenic features, the light carbon isotope values are taken to indicate oxidation of seeping hydrocarbons. The dolocretes are interpreted as groundwater precipitates near the water table of a brackish water body formed at a time of higher relative sea level than today.

Epigenetic barite concretions embedded within reworked mud balls occur in the upper Kuwait Group fluviatile clastic in southern Kuwait. The barite was precipitated displacively within flood plain muds during an epigenetic stage, possibly as a result of mixing of barium-rich brines with sulfate rich water. The mud balls formed during erosion of the barite-bearing flood plain mud layers by flood mass wasting.