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<p>The Como Member of the N’zémé Asso Formation (early Aptian) represents a continental sedimentary succession deposited within the North-Gabon Coastal Basin. This study presents a detailed facies analysis of four drill cores recovered from borehole CN1, located on Coniquet Island (18 Km SE of Libreville). Systematic macroscopic sedimentological description led to the identification of twenty-five sedimentary facies (F1-F25), grouped into four facies associations (FA-I to FA-IV). FA-I records a transitional fluvio-lacustrine system dominated by unidirectional fluvial currents evolving towards marginal lacustrine conditions. FA-II represents a deep, anoxic to dysoxic lacustrine environment characterised by organic matter preservation, framboidal pyrite deposits, and turbiditic sedimentation, corresponding to a flooding maximum. FA-III reflects a prograding deltaic system with variable hydrodynamic conditions and episodes of carbonate precipitation in an alkaline lacustrine setting. FA-IV documents a shallow carbonate lake-to-playa environment subjected to intense evaporation under arid-to-semi-arid climatic conditions, constituting a pre-evaporite phase that directly precedes the evaporite materials of the overlying Ezanga Formation. The vertical succession of these associations records a complex palaeoenvironmental evolution driven by post-rift thermal subsidence and a major climatic transition from arid towards progressively more humid climate during the early Aptian. These results provide new insights into the sedimentary and palaeoenvironmental evolution of the North-Gabon Coastal Basin and contribute to a broader understanding of Early Cretaceous continental basins along the West African margin.</p>

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Facies analysis and depositional environment of the Como member (N’zémé Asso formation, early Aptian) deposits in North Gabon Basin

  • 期刊论文

  • 发表日期：

    2026年5月18日

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  • Urlain Gaël Yakouya-Moubamba,
  • Lauriss-Paule Ngombi-Pemba,
  • Wilma Linda-Belle Mougola,
  • Mohamed Benzaggagh,
  • Benjamin Musavu Moussavou

摘要

The Como Member of the N’zémé Asso Formation (early Aptian) represents a continental sedimentary succession deposited within the North-Gabon Coastal Basin. This study presents a detailed facies analysis of four drill cores recovered from borehole CN1, located on Coniquet Island (18 Km SE of Libreville). Systematic macroscopic sedimentological description led to the identification of twenty-five sedimentary facies (F1-F25), grouped into four facies associations (FA-I to FA-IV). FA-I records a transitional fluvio-lacustrine system dominated by unidirectional fluvial currents evolving towards marginal lacustrine conditions. FA-II represents a deep, anoxic to dysoxic lacustrine environment characterised by organic matter preservation, framboidal pyrite deposits, and turbiditic sedimentation, corresponding to a flooding maximum. FA-III reflects a prograding deltaic system with variable hydrodynamic conditions and episodes of carbonate precipitation in an alkaline lacustrine setting. FA-IV documents a shallow carbonate lake-to-playa environment subjected to intense evaporation under arid-to-semi-arid climatic conditions, constituting a pre-evaporite phase that directly precedes the evaporite materials of the overlying Ezanga Formation. The vertical succession of these associations records a complex palaeoenvironmental evolution driven by post-rift thermal subsidence and a major climatic transition from arid towards progressively more humid climate during the early Aptian. These results provide new insights into the sedimentary and palaeoenvironmental evolution of the North-Gabon Coastal Basin and contribute to a broader understanding of Early Cretaceous continental basins along the West African margin.