SABKHA CYCLES IN THE ARAB/DARB FORMATION OFF THE TRUCIAL COAST OF ARABIA

SUMMARY Study of 176 ft. (53.7 m) of core from the Arab/Darb Formation of the Umm Shaif Field, Abu Dhabi Marine Areas, has revealed a sequence of sediments which can be related to nine distinct cycles of sabkha formation. The sabkha cycle consists of a basal algal grainstone/boundstone (which is interpreted as a shoal) passing upwards through lagoonal dolomite, intertidal algal mat and into a final supratidal development of nodular anhydrite and associated dolomite. Dolomiti‐sation and the formation of nodular anhydrite were early‐stage products of diagenesis. Poikilotopic anhydrite is common in the lagoonal dolomites but it is thought that this was not formed until the sediment was completely lithified. Stylolites, although of small amplitude, are more common in dolomite than in limestone; a generalisation which is at variance with earlier observations.