Intra‐shoreface erosion in response to rapid sea‐level fall: depositional record of a tectonically uplifted strand plain, Pacific coast of Japan
Intra‐shoreface erosion in response to rapid sea‐level fall: depositional record of a tectonically uplifted strand plain, Pacific coast of Japan
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DOI：
10.1111/j.1365-3091.2007.00876.x
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发表时间：
2007-10
期刊：
影响因子：
3.5
通讯作者：
T. Tamura;F. Nanayama;Y. Saito;F. Murakami;R. Nakashima;Kazuaki Watanabe
中科院分区：
文献类型：
--
作者：
T. Tamura;F. Nanayama;Y. Saito;F. Murakami;R. Nakashima;Kazuaki Watanabe
这项研究记录了降低冲浪区（即上岸面）导致近年侵蚀的情况，在全新世的两个快速的相对海平面沿构造隆起的海岸落下，以及由此产生的编程岸上沉积物的特征基于从日本东部太平洋海岸的Kujukuri Strand Plain获得的三个新钻芯的高分辨率分析和放射性碳年代。先前发布的有关现代海岸线轮廓调整的信息和信息。 2·6和1·8至2·0 ka是通过下岸设施的底座来记录的，并通过降低上下岸面设施之间的侵蚀边界来记录。相邻的现代海滩的叠加床特征定义了一个信封，其底座反映了长岸条和麻烦的海岸迁移比平均海滩剖面是向上凹的，并且在上面的shoreface的下限上表现出平坦的平台，等同于风暴冲浪区该表面的海向过渡，而不是平均相等的谱系，将米级尺度控制为kujukuri shoreface沉积的尺度内部结构。以及长岸酒吧和麻烦的迁移。
This study documents lowering of the surf zone (i.e. the upper shoreface) leading to intra‐shoreface erosion, following two rapid relative sea‐level falls along a tectonically uplifted coast during the Holocene, and the characteristics of the resultant prograding shoreface deposits. These findings are based on high‐resolution analysis and radiocarbon dating of three new drill cores obtained from the Kujukuri strand plain, Pacific coast of eastern Japan, combined with previously published borehole data and information on modern shoreline profile adjustments. A shallowing‐upward sandy succession composed of lower and upper shoreface facies, foreshore and backshore facies was recognized in the drill cores. Two rapid falls in relative sea‐level at 2·3 to 2·6 and 1·8 to 2·0 ka are recorded by downstepping of the base of the foreshore facies, and farther seawards by the lowering of an erosional boundary between the upper and lower shoreface facies. Superimposed bed profiles of an adjacent modern beach define an envelope, the base of which reflects shore‐normal migration of longshore bars and troughs. The base of the envelope represents an erosional surface that divides the surface mobile layer above from preserved deposits beneath. The surface is concave upwards and steeper than the mean beach profile, and exhibits a flat platform approximately at the lower limit of the upper shoreface equating to the storm surf zone. The seaward transition of this surface, rather than the mean equilibrium profile, controls the metre‐scale to decimetre‐scale internal structure of the Kujukuri shoreface deposits. Depositional models for sea‐level fall based on an exponential equilibrium profile do not adequately account for the presence and migration of longshore bars and troughs.