An assessment of coastal tectonics along the Sanriku coast, northeast Japan, from a Holocene sedimentary succession in the Kuji plain
An assessment of coastal tectonics along the Sanriku coast, northeast Japan, from a Holocene sedimentary succession in the Kuji plain
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DOI：
10.1016/j.margeo.2020.106165
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发表时间：
2020-06
期刊：
影响因子：
2.9
通讯作者：
Y. Niwa;T. Sugai
中科院分区：
文献类型：
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作者：
Y. Niwa;T. Sugai
构造活动区的全新世沉积序列是理解海岸构造的关键，因为它们提供了千年尺度地壳运动的信息。最近对2011年东北冲地震震源区附近的三陆海岸沿着全新世沉积序列的分析报告了海岸中部到南部的千年尺度沉降，但只有一个可比较的数据集可用于海岸的北方。为了全面了解三陆海岸沿着千年尺度的地壳运动，我们从海岸北方的久治平原获得了年代久远的全新世沉积物岩心。这些岩心记录了一个约1000年以来的海侵障壁-泻湖体系。9500至8000 cal BP，一个从约9500至8000 cal BP的退积前三角洲至三角洲前缘。8000至6500 cal BP，以及随后的波浪影响的浅海和河流环境。从当时的沉积环境估计的研究区早中全新世的相对海平面高于在津轻石平原，中部三陆海岸，在那里千年尺度的沉降，以前推断。这种差异表明，在千年尺度上，久慈平原相对于津轻石平原已经隆起。三陆海岸北方的相对隆起与最近推测的三陆海岸中部至南部的沉降之间千年尺度地壳运动的对比证实了三陆海岸包含多个地壳变形区。此外，这种千年尺度地壳运动的空间分布与最近报道的MIS 5海洋阶地分布非常一致，表明自约200年以来，三陆海岸一直有沿着向南倾斜的趋势。100 ka。
Holocene sedimentary successions in tectonically active regions are key to understanding coastal tectonics, because they provide information on millennial-scale crustal movements. Recent analyses of Holocene sedimentary successions along the Sanriku coast, near the source region of the 2011 Tohoku-oki earthquake, have reported millennial-scale subsidence in central to southern parts of the coast, but only one comparable dataset is available for the northern part of the coast. To obtain a comprehensive understanding of millennial-scale crustal movements along the Sanriku coast, we obtained well-dated Holocene sediment cores from the Kuji plain in the northern part of the coast. These cores record a transgressive barrier-lagoon system from ca. 9500 to 8000 cal BP, a regressive prodelta to delta front from ca. 8000 to 6500 cal BP, and a subsequent wave-influenced shallow marine and fluvial environment. The early to mid-Holocene relative sea level in the study area estimated from the sedimentary environment at that time is higher than that in the Tsugaruishi plain, central Sanriku coast, where millennial-scale subsidence was previously inferred. This discrepancy indicates that the Kuji plain has been uplifted relative to the Tsugaruishi plain on a millennial scale. The contrast in the millennial-scale crustal movements between relative uplift on the northern Sanriku coast and recently inferred subsidence on the central to southern Sanriku coast confirms that the Sanriku coast contains multiple areas of crustal deformation. Furthermore, this spatial distribution of millennial-scale crustal movements is in good agreement with the recently reported MIS 5 marine terrace distribution, suggesting a continuous southward tilting trend along the Sanriku coast since ca. 100 ka.