FACIES ANALYSIS AND EARLY DIAGENESIS OF THE MIDDLE-LATE EOCENE DAMMAMFORMATION, ABU-DHABI, UNITED-ARAB-EMIRATES

Within onshore Abu Dhabi, United Arab Emirates, the Middle-Late Eocene Dammam Formation can be separated into three distinct units on the ba sis of lithological analysis. Petrographic analysis shows these units to consist of interbedded yellow-brown marl and shale with gray biocla stic packstone/grainstones and mudstone/wackestones. Dolomite and gyps um occur locally in the upper half of the section A lithostratigraphy and facies analysis of the Dammam suggests cycling between the grain-s upported and mud-supported limestones, and with pulses of terrigenous material producing the marry and shaley interbeds. The diagenetic hist ory of the Dammam is dominantly a reduction of porosity primarily due to secondary cementation by two generations of calcite and the recryst allization of unstable grains and cement, as opposed to dissolution In addition, dolomitization, which often has the effect of creating good secondary porosity, which is only local in extent. The Dammam of the onshore Abu Dhabi is interpreted in the area to represent a transition al period between the more restricted limestones of the underlying Low er Eocene Rus Formation and the more complex sub-environments of the o verlying Oligocene Asmari Formation.