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Sedimentological and ichnological characteristics on macrotidal Baeksu tidal shoreface, southwestern coast of Korea
Marine Geology ( IF 2.9 ) Pub Date : 2021-08-19 , DOI: 10.1016/j.margeo.2021.106607
Byongcheon Yang 1 , Tae Soo Chang 2 , Robert W. Dalrymple 3
Affiliation  

Integrated sedimentologic and ichnologic studies along the Baeksu coast of southwestern Korea have revealed that despite the macrotidal conditions, the morphologic characteristics and preserved deposits of the intertidal flats show strong similarities to those commonly reported from wave-dominated shorefaces. Morphologically, a beachface is developed near the high-tide level, which is backed by the high-tide mud flat and fronted by the extensive intertidal shoreface (sensu Dashtgard et al., 2021), where wave-formed swash bars are present. Although sedimentation is strongly influenced by seasonal winds and waves, the preserved deposits conspicuously comprise abundant storm beds that consist mainly of wave-rippled and hummocky cross-stratified sands, because summer muds are typically ephemeral. The storm beds, which are predominant and thick near the low-tide line, become thinner in a landward direction, due to the progressive dissipation of wave-energy by bottom friction. Such physical processes, exerted on tidal-shoreface sedimentation, are also reflected in the ichnofacies distribution, showing that distal expressions of the Skolithos Ichnofacies characterize the lower intertidal zone and are replaced landward by proximal expressions of the Cruziana Ichnofacies. Except for the low-BI beachface (BI 0–1), the intensities of bioturbation generally increase in a landward direction (BI 0–1 to BI 3–4), in correspondence with the physical-energy distribution.

The study area reveals that the sedimentological and ichnological characteristics commonly employed to recognize wave-dominated shoreface settings (even including high-wave-energy tidal-shoreface counterparts) apparently show a reverse trend within the intertidal shoreface, probably overlying the normal-trend, subtidal shoreface. Although these findings have not been broadly tested, we, however, believe that these features are representative of the low-energy end of the full spectrum of wave-dominated coastal settings.



中文翻译:

韩国西南海岸大潮白水潮汐岸面沉积和地质特征

韩国西南部白水海岸的沉积学和地质学综合研究表明,尽管存在大潮汐条件,但潮间带滩涂的形态特征和保存的沉积物与通常报告的以波浪为主的海岸面有很强的相似性。形态上,靠近高潮位发育滩面,背靠高潮泥滩,正面为广阔的潮间带岸面(sensu Dashtgard 等人,2021 年),其中存在波形斜杠。尽管沉积受到季节性风和波浪的强烈影响,但保存下来的沉积物明显包含丰富的风暴床,这些风暴床主要由波浪纹和丘状交叉层状沙子组成,因为夏季泥浆通常是短暂的。由于底部摩擦力逐渐耗散波浪能,在低潮线附近占主导地位且较厚的风暴床在向陆方向变薄。这种作用于潮汐-岸面沉积的物理过程也反映在地层相分布中,表明Skolithos地层相的远端表现是低潮间带的特征,向陆方向被Cruziana 的近端表现所取代地貌。除了低 BI 滩面(BI 0-1)外,生物扰动强度通常在向陆方向(BI 0-1 到 BI 3-4)增加,与物理能量分布相对应。

研究区表明,通常用于识别波浪主导的滨面环境(甚至包括高波能潮汐滨面)的沉积学和地质学特征在潮间带滨面内明显显示出相反的趋势,可能覆盖在正常趋势、潮下岸面。尽管这些发现尚未经过广泛测试,但我们相信这些特征代表了波浪主导的沿海环境的全谱低能量端。

更新日期:2021-08-21
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