Holocene dolomites in supratidal carbonate beds south of Abu Dhabi are polygenetic. The overall distribution of most authigenic dolomite is controlled primarily by a pre-Holocene Pleistocene sand topography.

Two types of dolomites are present: (1) a series of disordered calcium-rich dolomites (Ca⁵²Mg⁴⁸-Ca⁵⁷Mg⁴³), and (2) a disordered stoichiometric dolomite (Ca⁵⁰Mg⁵⁰). Dolomitic carbonate muds contain various combinations of calcium-rich dolomite species and/or stoichiometric dolomite.

Calcium-rich dolomites have two origins. A major part is formed by reaction of aragonite and magnesium calcite with seawater-derived brines ("marine dolomite"), and a minor but locally significant part is formed by reaction of aragonite and calcite with continental groundwaters. The stoichiometric dolomite is detrital and of wind-blown origin. Authigenic dolomites form the major fraction, but locally 25% is detrital dolomite.

Distribution of authigenic "marine dolomite" is controlled by interrelated factors of (1) sedimentary facies, (2) surface relief, and (3) frequency of seawater flooding. These factors are in turn controlled by the pre-Holocene sand topography. Dolomitization is most extensive (to 100% dolomite) in buried, former intertidal sediments composed of an algal-laminated aragonitic mud facies and a burrowed aragonitic mud facies. Rocks in the latter facies are more completely dolomitized, probably because of their greater permeability. An underlying subtidal skeletal aragonitic mud facies is only partly dolomitized (5-15% dolomite).

The dolomitized buried facies attain their greatest areal distribution underlying elongate supratidal areas of low relief. These areas, because of their relief and orientation, are frequently flooded with sea-water resulting in input of brines with ^mCa²⁺/^mMg²⁺ ratios > 30 for dolomitization. These supratidal areas of low

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relief are ancestral to tidal channels cut into the underlying Pleistocene sandstone beds.

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