The Diagenesis of Middle Eocene Sandstones from the Western Thrace Basin, Turkey

The diagenetic history of the middle Eocene sandstones of the western Thrace Basin is described based on petrological analysis of samples from four boreholes. Diagenesis in the sandstones principally involves the progressive development of various types of cements in the fallowing order: chlorite authigenesis, siderite crystallization, illite rim formation, quartz overgrowths, and late Fe-calcite cement. After the formation ofthe cementation phases, there was a disssolution phase creating secondary porosity via the dissolution of carbonate and feldspars, accompanied by generation of a late kaolinite-cementing phase. The latter processes are thought to be related to generation of acidic pore waters generated by the maturation of organic matter in the middle Eocene shales.