Holocene shallow-water carbonate and evaporite sediments are forming in the Khor al Bazam, a saline lagoon on the coast of Abu Dhabi, southwest Persian Gulf. The sediments are composed of (1) skeletal grains, including whole and fragmented mollusks, corals, calcareous algae, bryozoans, foraminifers, and ostracods; (2) nonskeletal grains, including oolites, pellets, and pellet aggregates; (3) carbonate mud; (4) noncarbonate minerals including gypsum, anhydrite, and terrigenous quartz; and (5) organic material incorporated within mud and carbonate grains.

Lithofacies are (1) coral and coralline-algae facies, (2) oolitic sand facies, (3) pellet-aggregate and pellet facies, (4) mud and pellet facies, (5) molluscan sand facies, (6) algal mat facies, and (7) evaporite facies.

Nonskeletal calcium carbonate sediment types are related to wave energy; oolites form in the most turbulent environments, pellet aggregates in moderately sheltered environments, and pellets and muds in areas of low wave energy.

Skeletal material is altered by blue-green algae. The grains contain algal cells and threads invested in mucilage. Respiration and photosynthesis by algae dissolve the original shell material and reprecipitate microcrystalline aragonite. Chemical changes within the investing organic material cause blackening of some of the carbonate grains.