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<p>The Ordovician strata in the western Taebaeksan Basin have remained poorly understood due to structural complexity, pervasive dolomitization, and limited fossil recovery. This study establishes a refined chronostratigraphic framework for the uppermost Yeongwol Group, based on new lithostratigraphic and conodont biostratigraphic data from the Changri and Samokri sections of the Yeongheung Formation. Two conodont faunal assemblages are recognized: the Darriwilian <i>Plectodina onychodonta</i> Faunal Assemblage and the Sandbian <i>Tasmanognathus sishuiensis</i>-<i>Microcoelodus asymmetricus</i> Faunal Assemblage. The latter occurs directly beneath a disconformity known as the Great Hiatus and is overlain by the Bashkirian <i>Idiognathoides sinuatus</i> Faunal Assemblage of the Yobong Formation. These findings demonstrate that the Yeongwol Group extends into the Sandbian and is broadly coeval with the Hoedongri Formation of the Yongtan Group and the Fengfeng Formation of the North China Platform. All recognized conodont assemblages and biozones in the Taebaeksan Basin share faunal affinities with North China, supporting the interpretation of deposition along the same continental margin. The Great Hiatus is interpreted as a regional-scale disconformity lacking angular discordance between bedding planes, implying relative tectonic stability across the Sino-Korean Block during the Paleozoic. However, the approximately 10-million-year difference in the stratigraphic gap between the western and eastern Taebaeksan Basin suggests not only that the western area experienced less denudation, but also that it underwent earlier marine transgression during the Late Paleozoic.</p>

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First integrated documentation of Sandbian strata and the Great Hiatus disconformity in the western Taebaeksan Basin, Yeongwol, Korea: implications for basin evolution and tectonic history

  • 期刊论文

  • 发表日期：

    2025年11月20日

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  • Byung-Su Lee,
  • Jino Park,
  • Zhongyang Chen

摘要

The Ordovician strata in the western Taebaeksan Basin have remained poorly understood due to structural complexity, pervasive dolomitization, and limited fossil recovery. This study establishes a refined chronostratigraphic framework for the uppermost Yeongwol Group, based on new lithostratigraphic and conodont biostratigraphic data from the Changri and Samokri sections of the Yeongheung Formation. Two conodont faunal assemblages are recognized: the Darriwilian Plectodina onychodonta Faunal Assemblage and the Sandbian Tasmanognathus sishuiensis-Microcoelodus asymmetricus Faunal Assemblage. The latter occurs directly beneath a disconformity known as the Great Hiatus and is overlain by the Bashkirian Idiognathoides sinuatus Faunal Assemblage of the Yobong Formation. These findings demonstrate that the Yeongwol Group extends into the Sandbian and is broadly coeval with the Hoedongri Formation of the Yongtan Group and the Fengfeng Formation of the North China Platform. All recognized conodont assemblages and biozones in the Taebaeksan Basin share faunal affinities with North China, supporting the interpretation of deposition along the same continental margin. The Great Hiatus is interpreted as a regional-scale disconformity lacking angular discordance between bedding planes, implying relative tectonic stability across the Sino-Korean Block during the Paleozoic. However, the approximately 10-million-year difference in the stratigraphic gap between the western and eastern Taebaeksan Basin suggests not only that the western area experienced less denudation, but also that it underwent earlier marine transgression during the Late Paleozoic.