Small quantities of a rare Ca-deficient dolomite have been found coexisting in thin layers and alternating with the normal Ca-rich variety in the Holocene sabkhas of southern Kuwait. The Ca-poor dolomite has a molar composition of Ca46–49, whereas the Ca-rich type is Ca51–56. The former type has been found only in two localities of the supratidal zone that are not subjected to tidal flooding today, and mostly within the fluctuating ground-water table in these zones. The thin layers are either carbonate mud-rich or pellet-rich, and the amount of Ca-poor dolomite is never more than 4 to 6 per cent by weight of the total carbonate fraction. The dolomites vary in size between 2 μm and 5 μm and exhibit characteristic rhombic crystal morphologies.