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<p>This study explores the Permian mixed siliciclastic-carbonate facies and their depositional environments in southern Tunisia (part of Northern Gondwana). It relies on a facies analysis of the Jebel Tebaga outcrops in Medenine, supplemented by data from two key petroleum wells located to the north and south. The carbonate facies comprise sponge-algal patch reefs embedded within fossiliferous shales, formed in a low-energy outer ramp setting, massive bioherms built by encrusting algae formed in shelf margin conditions. The well-bedded limestones and fringing patch reefs developed in the inner shelf setting. The middle to late Permian ramp siliciclastic facies of the Tebaga outcrops contain various trace fossils assigned to the <i>Cruziana</i> ichnofacies, while those of the latest Permian are primarily associated with a meandering fluvial system characterized by floodplain red beds. The vertical and lateral facies distribution from the middle to late Permian reveals repeated shifts from a mixed siliciclastic-carbonate ramp system to a rimmed carbonate platform, reflecting variations in carbonate sedimentation rates linked to sea level fluctuations. N-S surface-to-subsurface stratigraphic correlation shows that the carbonate and siliciclastic facies represent a range of depositional environments, extending from inner to middle shelf facies in the south, shelf margin environment with reefs along the Tebaga outcrops, as well as a subsiding area to the north (TB-1 well) makred by a significant shaly succession (3900 m), including thin turbiditic sandstones and repeatedly resedimented carbonate materials derived from a nearby platform. For the first time, this study interprets the sedimentary record of the TB-1 well as indicative of a foredeep setting. The middle to late Permian regressive sedimentary evolution from marine to continental settings illustrates the gradual eastward withdrawal of the Permian Sea from Tunisia. was controlled by a pronounced sea-level fall and the influence of the Variscan orogeny during the late Permian.&#xa0;</p>

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New insights on the Permian mixed siliciclastic and carbonate deposits of southern Tunisia: Facies, palaeoenvironments, and depositional models

  • 期刊论文

  • 发表日期：

    2025年6月27日

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  • Ali Khachira,
  • Mohamed Soussi,
  • Alfred Uchman

摘要

This study explores the Permian mixed siliciclastic-carbonate facies and their depositional environments in southern Tunisia (part of Northern Gondwana). It relies on a facies analysis of the Jebel Tebaga outcrops in Medenine, supplemented by data from two key petroleum wells located to the north and south. The carbonate facies comprise sponge-algal patch reefs embedded within fossiliferous shales, formed in a low-energy outer ramp setting, massive bioherms built by encrusting algae formed in shelf margin conditions. The well-bedded limestones and fringing patch reefs developed in the inner shelf setting. The middle to late Permian ramp siliciclastic facies of the Tebaga outcrops contain various trace fossils assigned to the Cruziana ichnofacies, while those of the latest Permian are primarily associated with a meandering fluvial system characterized by floodplain red beds. The vertical and lateral facies distribution from the middle to late Permian reveals repeated shifts from a mixed siliciclastic-carbonate ramp system to a rimmed carbonate platform, reflecting variations in carbonate sedimentation rates linked to sea level fluctuations. N-S surface-to-subsurface stratigraphic correlation shows that the carbonate and siliciclastic facies represent a range of depositional environments, extending from inner to middle shelf facies in the south, shelf margin environment with reefs along the Tebaga outcrops, as well as a subsiding area to the north (TB-1 well) makred by a significant shaly succession (3900 m), including thin turbiditic sandstones and repeatedly resedimented carbonate materials derived from a nearby platform. For the first time, this study interprets the sedimentary record of the TB-1 well as indicative of a foredeep setting. The middle to late Permian regressive sedimentary evolution from marine to continental settings illustrates the gradual eastward withdrawal of the Permian Sea from Tunisia. was controlled by a pronounced sea-level fall and the influence of the Variscan orogeny during the late Permian.