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Post-collisional sedimentation of the Early Mesozoic Munamdong Formation in South Korea
Geological Journal ( IF 1.4 ) Pub Date : 2022-09-16 , DOI: 10.1002/gj.4588 Younggi Choi 1 , Yong Sik Gihm 2
Geological Journal ( IF 1.4 ) Pub Date : 2022-09-16 , DOI: 10.1002/gj.4588 Younggi Choi 1 , Yong Sik Gihm 2
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Post-collisional processes cause uplift and exhumation of the overthickened crust together with the formation of sedimentary basins. To determine the influence of post-collisional processes on sedimentation, we investigated the Early Mesozoic Munamdong Formation of the Yuljeon Basin in the Korean Peninsula, deposited immediately after the orogenic events caused by the collision of the North China Block and South China Block. Facies analysis shows that the Munamdong Formation was deposited in a streamflow-dominated alluvial fan under tropical/subtropical climatic conditions. Vertically, the Munamdong Formation exhibits a fining-upward trend with changes in stacking patterns, from highly amalgamated channel conglomerates to floodplain fines, indicating a progressive increase in the creation of accommodation space exceeding sediment supply. Moreover, the types of gravels in the conglomerate beds and the petrographic characteristics of the sandstones suggest that the sediments were supplied rapidly from nearby Precambrian high-grade metamorphic rocks and Triassic post-collisional plutons. These results indicate the supply of sediment from restricted sources, implying that the drainage basins did not widen even during intermittent quiescence of basin subsidence. We interpret the fining-upward trend and uniform composition of sediments to have resulted from rapid uplift and exhumation of the orogenic crust, together with rapid tectonic subsidence, possibly aided by post-collisional magmatism. This study shows that the Munamdong Formation reflects a close connection between surficial sedimentation and post-collisional tectonic processes. This study will help to fill the gap of understanding between deep crustal processes and post-collision sedimentation with insight into the Early Mesozoic tectonic environment of the East Asian continental margins.
中文翻译：
韩国早中生代文南洞组碰撞后沉积
碰撞后过程导致加厚的地壳隆起和折返以及沉积盆地的形成。为了确定碰撞后过程对沉积的影响，我们研究了朝鲜半岛栗田盆地的早中生代文南洞组，该组在华北地块和华南地块碰撞引起的造山事件之后立即沉积。相分析表明，在热带/亚热带气候条件下，Munamdong 组沉积在以水流为主的冲积扇中。垂直方向上，Munamdong 地层随着堆积模式的变化呈现出向上变细的趋势，从高度混合的河道砾岩到漫滩细粒，表明可容空间的形成逐渐增加超过沉积物供应。而且，砾岩床中砾石的类型和砂岩的岩相特征表明，沉积物是由附近的前寒武纪高级变质岩和三叠纪碰撞后深成岩快速供给的。这些结果表明沉积物的供应来自受限的来源，这意味着即使在盆地沉降的间歇性静止期间，流域盆地也没有扩大。我们将沉积物的细化上升趋势和均匀成分解释为造山地壳的快速抬升和折返，以及快速的构造沉降，可能受到碰撞后岩浆作用的帮助。这项研究表明，文南洞组反映了地表沉积与碰撞后构造过程之间的密切联系。
更新日期：2022-09-16
中文翻译：
韩国早中生代文南洞组碰撞后沉积
碰撞后过程导致加厚的地壳隆起和折返以及沉积盆地的形成。为了确定碰撞后过程对沉积的影响，我们研究了朝鲜半岛栗田盆地的早中生代文南洞组，该组在华北地块和华南地块碰撞引起的造山事件之后立即沉积。相分析表明，在热带/亚热带气候条件下，Munamdong 组沉积在以水流为主的冲积扇中。垂直方向上，Munamdong 地层随着堆积模式的变化呈现出向上变细的趋势，从高度混合的河道砾岩到漫滩细粒，表明可容空间的形成逐渐增加超过沉积物供应。而且，砾岩床中砾石的类型和砂岩的岩相特征表明，沉积物是由附近的前寒武纪高级变质岩和三叠纪碰撞后深成岩快速供给的。这些结果表明沉积物的供应来自受限的来源，这意味着即使在盆地沉降的间歇性静止期间，流域盆地也没有扩大。我们将沉积物的细化上升趋势和均匀成分解释为造山地壳的快速抬升和折返，以及快速的构造沉降，可能受到碰撞后岩浆作用的帮助。这项研究表明，文南洞组反映了地表沉积与碰撞后构造过程之间的密切联系。
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