Growth And Demise Of A Paleocene Isolated Carbonate Platform, Northwest Sirte Basin, Libya: Sequence Stratigraphic Architecture And Controlling Factors


Isolated carbonate platforms are important for their significant explorational interests and tectonic sedimentary implications for the formation of extensional rift basins. This study integrates three-dimensional seismic and well data to investigate the architecture and growth history and interpret factors controlling the growth and termination of a Paleocene isolated carbonate platform in the West Mabruk field of the tectonically complex Sirte rift basin, Libya. The platform contains five seismic stratigraphic sequences bounded by unconformable sequence boundaries. Those seismic sequences are ∼450-550 m thick in two-way traveltime and have an aerial extension of at least 113 km2. Six major seismic facies show complex lithologies and depositional systems. Four major depositional environments are defined based on seismic facies and attributes as platform interiors (lagoon) with patch reefs, barrier reefs, slopes, and intraplatform seaways. Platform growth initiated in the early Paleocene as patch reefs formed on top of a Cretaceous horst and was terminated in the late Paleocene by a subaerial exposure. The platform developed through aggradation on the interior, margins, and intraplatform seaway and progradation on the slopes. The easterly trade winds generated an east-west energy flux that may be responsible for the prograding leeward margin and near-vertical aggrading windward margin. Tectonic subsidence generated by rifting of the Sirte Basin during the Late Cretaceous, coupled with repeated eustatic sea-level changes, created space for the growth of the carbonate platform. The Cretaceous horst served as a shallow-water positive-antecedent topography for the sediment nucleation. The internal stratigraphic heterogeneity and sequence development were influenced by short-term sea-level fluctuations, which may be resolved as third-order cycles on the seismic scale. The results of this work provide insights into the formation of isolated platforms in a rift setting, which can be used to predict the depositional systems and lithofacies that may contain hydrocarbon reservoirs. The depositional model can be used as an analogue for similar carbonate platforms worldwide.


Geosciences and Geological and Petroleum Engineering


Ministry of Higher Education and Scientific Research, Grant None

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Article - Journal

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Publication Date

01 Oct 2023