Lithostratigraphy of the Middle Eocene Dammam Formation in Qatar, Arabian Gulf: effects of sea-level fluctuations along a tidal environment

Abstract

The Middle Eocene Dammam Formation dominates the surface exposure of Qatar. It consists of shales followed by limestone and is topped by dolomitic limestone. It is subdivided, from oldest to youngest, into the Midra Shale, Dukhan, Umm Bab and Abaruq members. Three patterns of facies dominate the formation. Shale–marl facies in the lower part, mudstone/wackestone/packstone facies in the middle part and argillaceous dolomitic wackestone/packstone facies in the upper part. The main fauna of the Dammam Formation include Nummulites, Alveolines, Linderines, shark teeth, molluscs and echinoderms. The Nummulites species are common, particularly within the middle members (Dukhan and Umm Bab members). Coarsening-upward parasequences reflect the cyclicity of the Eocene Dammam Formation in Qatar. At least three short-lived transgressive/regressive cyclothems can be recognized in sediments of the formation. These small-scale cycles resulted from fluctuations in sea level. A local hiatus is believed to separate these cycles in northeastern Qatar. A warm shallow marine environment was predominant as indicated by extensive dolomitization and the presence of Alveolines, Linderines and Nummulites with globular tests.