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<p>The late Paleocene-early Eocene Patala Formation at Nammal Gorge was examined to determine the paleoenvironment changes based on the facies analysis. The Patala Formation at the studied interval has interbedded deposits of shale, limestone, and marl. Lithostratigraphically, the formation consists of two lithofacies associations; shale and limestone interbeds (LFA-01) at the base, grading into an overlying thick shale unit that holds the Paleocene-Eocene boundary, followed by interbedded larger foraminifera-bearing limestone and shale lithofacies association (LFA-02), having a shale unit at the top of the studied section. The LFA-02 unit also hosts three closely spaced non-depositional surfaces at the top within limestone. These unconformities are likely associated with tectonic uplift that occurred during the early Eocene due to a migrating collision-related flexural wave. Three palynofacies assemblages were identified, reflecting depositional settings in a general proximal, oxic-shelf, and basin environment. The continuous presence of <i>Axiodinium</i> species and its increasing abundance upward indicates the presence of warm surface waters. Various palynofacies parameters such as Terrestrial/Marine (T/M), Peridiniacean/Gonyaulacacean (P/G), Palynological Marine Index (PMI), Opaque/Translucent phytoclast (O/TR), Opaque Equidimensional/ Opaque Lath (O-Eq/O-La) were applied to observe the proximal–distal trends. The environmental fluctuation is also evident from the smaller benthonic and Planktonic foraminiferal dominating assemblages in LFA-01 shale representing bathyal settings followed by LBF dominating LFA-02 representing shallow carbonate platform settings. Fossil assemblages, rock texture, and fabrics of the limestone in LFA-02 lead to the characterization of two microfacies (MF-1&amp;MF-2) corresponding to “shoal” inner shelf and middle shelf depositional settings. The palaeoenvironmental analysis suggests that the deposition in the late Paleocene-early Eocene in the studied section occurred in a wide spectrum of settings ranging from the open marine Bathyal to the shallow marine inner to the middle shelf. This short span of changes in paleoenvironmental settings is a reflection of the influence of local tectonic in an overall greenhouse condition resulting in higher sea levels elsewhere.</p>

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Inferring paleoenvironmental changes from integrated facies analysis of the late Paleocene-early Eocene succession, Salt Range, Pakistan

  • 期刊论文

  • 发表日期：

    2025年4月26日

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  • Muhammad Hanif,
  • Mahnoor Sabba,
  • Iftikhar Ahmed Abbasi,
  • Mohamed Abioui,
  • Nowrad Ali,
  • Muhammad Ishaq

摘要

The late Paleocene-early Eocene Patala Formation at Nammal Gorge was examined to determine the paleoenvironment changes based on the facies analysis. The Patala Formation at the studied interval has interbedded deposits of shale, limestone, and marl. Lithostratigraphically, the formation consists of two lithofacies associations; shale and limestone interbeds (LFA-01) at the base, grading into an overlying thick shale unit that holds the Paleocene-Eocene boundary, followed by interbedded larger foraminifera-bearing limestone and shale lithofacies association (LFA-02), having a shale unit at the top of the studied section. The LFA-02 unit also hosts three closely spaced non-depositional surfaces at the top within limestone. These unconformities are likely associated with tectonic uplift that occurred during the early Eocene due to a migrating collision-related flexural wave. Three palynofacies assemblages were identified, reflecting depositional settings in a general proximal, oxic-shelf, and basin environment. The continuous presence of Axiodinium species and its increasing abundance upward indicates the presence of warm surface waters. Various palynofacies parameters such as Terrestrial/Marine (T/M), Peridiniacean/Gonyaulacacean (P/G), Palynological Marine Index (PMI), Opaque/Translucent phytoclast (O/TR), Opaque Equidimensional/ Opaque Lath (O-Eq/O-La) were applied to observe the proximal–distal trends. The environmental fluctuation is also evident from the smaller benthonic and Planktonic foraminiferal dominating assemblages in LFA-01 shale representing bathyal settings followed by LBF dominating LFA-02 representing shallow carbonate platform settings. Fossil assemblages, rock texture, and fabrics of the limestone in LFA-02 lead to the characterization of two microfacies (MF-1&MF-2) corresponding to “shoal” inner shelf and middle shelf depositional settings. The palaeoenvironmental analysis suggests that the deposition in the late Paleocene-early Eocene in the studied section occurred in a wide spectrum of settings ranging from the open marine Bathyal to the shallow marine inner to the middle shelf. This short span of changes in paleoenvironmental settings is a reflection of the influence of local tectonic in an overall greenhouse condition resulting in higher sea levels elsewhere.