ABSTRACT
The Alamain hypersaline lagoons are perennial water bodies developed within the coastal sabkha flats of the northern margin of the Western Desert. This sabkha depression and the lagoons re isolated from the Mediterranean Sea by an oolitic carbonate ridge. The sediments of 12 cores were studied by XRD, SEM and DTA.
These lagoonal settings were always occur at the point of carbonate precipitation and where the hydrological conditions stable. However, the identification of scattered sulfate minerals may indicate infrequent periods of increased brine concentration.
The typical mineral association is comprised of aragonite, calcite and dolomite, intermixed with wind blown or dune washed quartz and feldspar. Aragonite and calcite occur as primary biogenic precipitates as well as diagenetic cements. Ferroan and non-ferroan dolomites are commonly found as primary precipitates in intergranular pore spaces of aggregate grains. Replacement dolomite is less frequent and commonly replaces aragonite in mollusc debris.
