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<p>During the Jurassic to Middle Eocene period (201–41 Ma), the Neo-Tethys established extensive platform sequences across the Hazara, Kashmir, and Potwar basins of the NW Himalayas, Pakistan. However, differential erosion and sedimentation resulting from tectonic uplift and subsidence created challenges in defining the aerial extent of the sedimentary strata. The Himalayan orogeny further complicated the establishment of a comprehensive sequence stratigraphic framework due to simultaneous sedimentation, thrusting, and uplift. There was a need to address these problems, so analyzing relative accommodation space and sedimentation rates was essential. The Hazara Basin experienced the deposition of a complete sequence of Jurassic-Middle Eocene. However, the Potwar and Kashmir basins were only submerged by flooding during the Paleocene. Above the fair-weather wave base (FWWB), regressive deltaic facies (Datta Formation) were deposited in the Lower Jurassic. With a transitional contact, transgressive shoreface-offshore facies (Shinawari Formation) were deposited below FWWB in the western Potwar Basin, with a sedimentation rate of 1–2.6 m/Ma. In contrast, the Datta and Shinawari formations were not deposited in the Hazara Basin. Regressive marginal marine settings (subtidal to supratidal) developed in the Hazara and western Potwar basins during the deposition of the Samana Suk Formation above the FWWB, with a sedimentation rate of 14.2 m/Ma, terminating in the Callovian. Lower Cretaceous transgressive facies (Chichali/Lumshiwal formations) deposited with a sedimentation rate 0.5–0.8 m/Ma below FWWB in the northern Hazara/western Potwar basins. Again, the sedimentation rate increased to 5.5 m/Ma below and above the FWWB, deposited outer-middle ramp facies of the Kawagarh Formation, and terminated in the Middle Cretaceous. The Paleocene sequence deposited middle-outer ramp facies below the FWWB, forming the MFS in the Patala Formation with a 1–30 m/Ma sedimentation rate. During Eocene, the sedimentation rate increased (85 m/Ma), and middle ramp/tidal-flat facies deposited above FWWB and terminated in the Bartonian due to the Himalayan uplift.</p>

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Relative change in accommodation space and sedimentation rates of Jurassic to Middle Eocene sedimentary facies in the NW Himalaya, Pakistan

  • 期刊论文

  • 发表日期：

    2025年5月3日

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  • Tariq Mahmood,
  • Naveed Ahsan,
  • Muhammad Armaghan Faisal Miraj,
  • Shaukat Ali,
  • Faisal Shah,
  • Syed Kamran Ali

摘要

During the Jurassic to Middle Eocene period (201–41 Ma), the Neo-Tethys established extensive platform sequences across the Hazara, Kashmir, and Potwar basins of the NW Himalayas, Pakistan. However, differential erosion and sedimentation resulting from tectonic uplift and subsidence created challenges in defining the aerial extent of the sedimentary strata. The Himalayan orogeny further complicated the establishment of a comprehensive sequence stratigraphic framework due to simultaneous sedimentation, thrusting, and uplift. There was a need to address these problems, so analyzing relative accommodation space and sedimentation rates was essential. The Hazara Basin experienced the deposition of a complete sequence of Jurassic-Middle Eocene. However, the Potwar and Kashmir basins were only submerged by flooding during the Paleocene. Above the fair-weather wave base (FWWB), regressive deltaic facies (Datta Formation) were deposited in the Lower Jurassic. With a transitional contact, transgressive shoreface-offshore facies (Shinawari Formation) were deposited below FWWB in the western Potwar Basin, with a sedimentation rate of 1–2.6 m/Ma. In contrast, the Datta and Shinawari formations were not deposited in the Hazara Basin. Regressive marginal marine settings (subtidal to supratidal) developed in the Hazara and western Potwar basins during the deposition of the Samana Suk Formation above the FWWB, with a sedimentation rate of 14.2 m/Ma, terminating in the Callovian. Lower Cretaceous transgressive facies (Chichali/Lumshiwal formations) deposited with a sedimentation rate 0.5–0.8 m/Ma below FWWB in the northern Hazara/western Potwar basins. Again, the sedimentation rate increased to 5.5 m/Ma below and above the FWWB, deposited outer-middle ramp facies of the Kawagarh Formation, and terminated in the Middle Cretaceous. The Paleocene sequence deposited middle-outer ramp facies below the FWWB, forming the MFS in the Patala Formation with a 1–30 m/Ma sedimentation rate. During Eocene, the sedimentation rate increased (85 m/Ma), and middle ramp/tidal-flat facies deposited above FWWB and terminated in the Bartonian due to the Himalayan uplift.