Microfacies analysis and depositional environments of the Middle Eocene (Bartonian) Qurn Formation along Qattamiya—Ain Sokhna district, Egypt

Abstract

The exposed Middle Eocene (Bartonian) Qurn Formation along Qattamiya—Ain Sokhna district is measured, sampled and microscopically investigated. Besides, the vertical distribution of the chemical oxides and strontium (Sr) has been determined to identify their petrographic, geochemical characteristics and interpret their depositional environments. The facies analysis (lithofacies, microfacies, and biofacies) of the studied rocks revealed the recognition of three microfacies associations: (1) restricted lagoon facies association (FT1–FT3), (2) open lagoon facies association (FT4–FT7), and (3) shoal facies association (FT8–FT9). Lithofacies and microfacies analysis of Middle Eocene rocks along Qattamiya—Ain Sokhna district reflect carbonate inner ramp regime ranging from restricted lagoon to shoal buildup depositional conditions. These identified inner ramp microfacies are changed eastward to mid-ramp, while they are represented westward by tidal flat and shallow lagoonal facies. The vertical distribution of both CaO and MgO revealed that MgO is related mainly to the dolomitization process rather than primary deposition. The vertical distribution of Sr in the studied carbonate samples matches with that of SiO2, thus may be related to the warm environmental conditions.