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<p>Eocene <i>Nummulites</i> banks play a significant role as potential hydrocarbon reservoirs. However, the impact of biological accumulation and sedimentary and diagenetic alterations on these rocks remains debated. Recent investigations of the El-Ramliya-Akheider block in northern Egypt utilized microfacies analysis, biometric measurements, and the analysis of taphonomic features to explore the origins of <i>Nummulites</i> accumulations. The first site, El-Ramliya, includes a well-bedded <i>Nummulites</i> bank- facies in ancient mid-ramp marine settings. The nummulitic wacke-/floatstone microfacies indicated auto-to parautochthonous origins, while the nummulitic pack-/rudstone microfacies suggested reworking by storm surges and wave action, potentially leading to para-to allochthonous origins. At the second site, Akheider, the biohermal <i>Nummulites</i> accumulation resembled a barrier, with deeper forebank molluscan nummulitic facies to the southeast. Both sites also featured A-form nummulitic wackestone microfacies in a back-bank lagoonal setting, likely formed under unfavorable ecological conditions. The dominance of porcelaneous Larger Benthic Foraminifera and mollusks in pack-/rudstone and wackestone microfacies indicated inner ramp back-bank lagoonal environments vertically upward from El-Ramliya banks and at the northwestern extension of Akheider bank. This tropical to subtropical ramp environment experienced warm, shallow marine conditions with variable nutrient levels. Storm events and eustatic sea level changes influenced the depositional cycles, leading to distinct transgressive and regressive phases within the <i>Nummulites</i> banks. The evolution of these accumulations reflects <i>Nummulites</i>’ ecological preferences, fluctuating sea levels, and warm middle Eocene climatic conditions.</p> Graphical abstract <p></p>

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Origin and evolution of Middle Eocene Nummulites accumulation in the El-Ramliya-Akheider Block, north Eastern Desert, Egypt: new sedimentological insights in a storm-dominated ramp setting

  • 期刊论文

  • 发表日期：

    2025年2月1日

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  • George Henry,
  • Mounir El-Azabi,
  • Walid Kassab

摘要

Eocene Nummulites banks play a significant role as potential hydrocarbon reservoirs. However, the impact of biological accumulation and sedimentary and diagenetic alterations on these rocks remains debated. Recent investigations of the El-Ramliya-Akheider block in northern Egypt utilized microfacies analysis, biometric measurements, and the analysis of taphonomic features to explore the origins of Nummulites accumulations. The first site, El-Ramliya, includes a well-bedded Nummulites bank- facies in ancient mid-ramp marine settings. The nummulitic wacke-/floatstone microfacies indicated auto-to parautochthonous origins, while the nummulitic pack-/rudstone microfacies suggested reworking by storm surges and wave action, potentially leading to para-to allochthonous origins. At the second site, Akheider, the biohermal Nummulites accumulation resembled a barrier, with deeper forebank molluscan nummulitic facies to the southeast. Both sites also featured A-form nummulitic wackestone microfacies in a back-bank lagoonal setting, likely formed under unfavorable ecological conditions. The dominance of porcelaneous Larger Benthic Foraminifera and mollusks in pack-/rudstone and wackestone microfacies indicated inner ramp back-bank lagoonal environments vertically upward from El-Ramliya banks and at the northwestern extension of Akheider bank. This tropical to subtropical ramp environment experienced warm, shallow marine conditions with variable nutrient levels. Storm events and eustatic sea level changes influenced the depositional cycles, leading to distinct transgressive and regressive phases within the Nummulites banks. The evolution of these accumulations reflects Nummulites’ ecological preferences, fluctuating sea levels, and warm middle Eocene climatic conditions.

Graphical abstract