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<p>The Pohang Basin is a Miocene basin located in the southeastern part of the Korean Peninsula and is one of the most intensively investigated. However, due to the absence of offshore deep-drilled core data, including basement rock, and the difficulties in onshore-offshore stratigraphic correlation, the initial stage of the basin formation and the entire sedimentary succession remain poorly understood. This study integrates newly acquired seismic profiles and deep-drilled core data to refine the depositional history and basin evolution of the offshore Pohang Basin in southeastern Korea. Core analysis revealed 18 sedimentary facies, grouped into five facies associations (FAs): FA1 (fluvial), FA2 (lacustrine), FA3 (delta), FA4 (inner- to mid-shelf), and FA5 (outer shelf to basin plain). The seismic profiles were divided into five major depositional units (Units I–V) based on the lap-out patterns and acoustic characteristics. The basal part of the drilled core comprises coarse-grained deposits of fluvial to deltaic origin, containing angular to subangular, poorly sorted dacitic to andesitic volcanic clasts. Additionally, time structure and isopach maps show that the initial succession (Unit I) was predominantly sourced from the south and east, in contrast to the prevailing interpretation that attributes the sediment supply to the western fan-delta system. These findings suggest that the basin was affected by multi-directional sediment feeding systems during its initial deposition. Based on the palynological assemblages and Sr isotope dating of drilled core samples, the top part of the depositional units was assigned to the middle Miocene. However, the presence of a thick trough fill, characterized by growth strata and compressional anticlines in a seismic record, suggests localized and continuous deposition, potentially extending into the late Miocene. This integrated approach refines previous basin development models by highlighting the multi-directional sediment feeding systems and structural complexity in basin infills.</p>

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Evolutionary history of the Pohang Basin reconstructed from offshore seismic and deep-drilled core data: evidence for an early Miocene multi-directional sediment-feeding system and late Miocene trough fills

  • 期刊论文

  • 发表日期：

    2025年6月6日

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  • Tae Yeon Kim,
  • Yi Kyun Kwon,
  • Yongmi Kim,
  • Gee Soo Kong,
  • Yoo Jin Kwon

摘要

The Pohang Basin is a Miocene basin located in the southeastern part of the Korean Peninsula and is one of the most intensively investigated. However, due to the absence of offshore deep-drilled core data, including basement rock, and the difficulties in onshore-offshore stratigraphic correlation, the initial stage of the basin formation and the entire sedimentary succession remain poorly understood. This study integrates newly acquired seismic profiles and deep-drilled core data to refine the depositional history and basin evolution of the offshore Pohang Basin in southeastern Korea. Core analysis revealed 18 sedimentary facies, grouped into five facies associations (FAs): FA1 (fluvial), FA2 (lacustrine), FA3 (delta), FA4 (inner- to mid-shelf), and FA5 (outer shelf to basin plain). The seismic profiles were divided into five major depositional units (Units I–V) based on the lap-out patterns and acoustic characteristics. The basal part of the drilled core comprises coarse-grained deposits of fluvial to deltaic origin, containing angular to subangular, poorly sorted dacitic to andesitic volcanic clasts. Additionally, time structure and isopach maps show that the initial succession (Unit I) was predominantly sourced from the south and east, in contrast to the prevailing interpretation that attributes the sediment supply to the western fan-delta system. These findings suggest that the basin was affected by multi-directional sediment feeding systems during its initial deposition. Based on the palynological assemblages and Sr isotope dating of drilled core samples, the top part of the depositional units was assigned to the middle Miocene. However, the presence of a thick trough fill, characterized by growth strata and compressional anticlines in a seismic record, suggests localized and continuous deposition, potentially extending into the late Miocene. This integrated approach refines previous basin development models by highlighting the multi-directional sediment feeding systems and structural complexity in basin infills.