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.
Highlights
Carbonate inner- to outer-ramps occur along the continental margin of Tethys (Santanu et al 2018)
At several intervals of the studied Abu Shama section, the rich-miliolid grainstone and packstone microfacies types can be recorded and reflect a restricted inner ramp depositional environment. These protected shallow-marine facies are changed into molluscan and echinoid grainstone and rudstone microfacies that can be deposited in an open lagoon environment
The lower part of the studied Qurn Formation in Qattamiya section is characterized by enrichment of miliolid, echinoids, and larger foraminiferal tests of Nummulites sp with rare planktonic foraminifera revealing a restricted inner ramp depositional environment
Summary
Carbonate inner- to outer-ramps occur along the continental margin of Tethys (Santanu et al 2018). These are dominated by larger benthic foraminifera, including nummulitid and alveolinid (Adabi et al 2008). The studying of larger foraminifera provides crucial evidence for paleoenvironmental settings of Paleogene carbonates (Bassi et al 2013; Hadi et al 2016). There is a well-defined Eocene sequence extending through east Cairo in an East–West direction. The Eocene rocks in Egypt are marked by varied lithologies and depositional environments ranging from continental to lagoonal, to outer neritic conditions (Sallam et al 2015a). The lithological complexity of these rock units and the influence of tectonic movements associated with the opening of
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