Stratigraphic reconstruction of the lower-;middle Miocene Goto Group, Nagasaki Prefecture, Japan.
Stratigraphic reconstruction of the lower-;middle Miocene Goto Group, Nagasaki Prefecture, Japan.
复制标题
日本长崎县下中新世五岛群地层重建。
DOI：
10.1111/iar.12456
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发表时间：
2022
期刊：
影响因子：
1.5
通讯作者：
Kenji Horie.
中科院分区：
文献类型：
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作者：
Shoichi Kiyokawa;Masaru Yasunaga;Ayako Yamamoto;Daisaku Kaneko;Yuta Ikebata;Noriko Hasebe;Yukiyasu Tsutsumi;Mami Takehara;Kenji Horie.
五岛列岛位于日本列岛的最西端，保存着大陆边缘裂谷和日本海开口期间沉积的中下新世沉积层序。五岛群的地层学和新的 K-Ar、裂变径迹和 U-Pb 年龄数据被用来确定日本西南部裂谷的初始条件。五岛群厚度为2000～3000米。下部单元（约 22–17.6 Ma）由厚厚的绿色火山碎屑岩和玄武岩火山物质组成，代表大陆裂谷的初始阶段。中间单元（约-17.6 Ma）由火山活动时期同裂谷沉积盆地的湖泊和蜿蜒河流环境中沉积的交替砂岩和页岩组成。上部单元（约 17.6–16.8 Ma）由厚厚的河流三角洲相砂岩组成，这些砂岩是在大陆边缘快速沉降过程中沉积的。该单元是由流入日本海的大型河流系统沉积的。这些序列包含相对较冷到较温暖的植物群（大岛型），并记录了中新世气候最适期的温暖时期。五岛长英质火山岩（16.8~15.4 Ma）不整合覆盖于五岛群之上，五岛群沉积后发生花岗岩岩浆作用（约16~14.5 Ma）。广泛的湖泊、曲流辫状河流和五岛群的巨大三角洲系统以及长英质火山活动，是由于欧亚大陆东缘火山弧裂谷早期阶段的快速沉降形成地垒盆地而形成的。这些事件发生在日本海形成之前和期间的 22.0 Ma 到 16.8 Ma。
The Goto Islands are located at the westernmost tip of the Japan archipelago, and preserve a lower–middle Miocene sedimentary sequence deposited during rifting of the continental margin and opening of the Sea of Japan. The stratigraphy of the Goto Group and new K–Ar, fission‐track, and U–Pb age data were used to determine the initial conditions of rifting in southwest Japan. The thickness of the Goto Group is 2000–3000 m. The lower unit (ca. 22–17.6 Ma) consists of thick, greenish, volcaniclastic rocks with basaltic volcanic material, representing the initial stages of continental rifting. The middle unit (ca. −17.6 Ma) consists of alternating sandstones and shales deposited in lacustrine and meandering fluvial environments in a syn‐rift sedimentary basin during a period of volcanic activity. The upper unit (ca. 17.6–16.8 Ma) consists of thick sandstones of fluvial–deltaic facies that were deposited during rapid subsidence at the continental margin. This unit was deposited by a large fluvial system that flowed into the Sea of Japan. These sequences contain relatively cooler to warmer flora (Daijima‐type) and record the warm period of the Miocene Climatic Optimum. The Goto felsic volcanic rocks (16.8 ~ 15.4 Ma) unconformably overlie the Goto Group, and granitic magmatism (ca. 16–14.5 Ma) occurred after sedimentation of the Goto Group. The widespread lacustrine, meandering–braided fluvial, and vast deltaic systems of the Goto Group, and felsic volcanism, were formed due to rapid subsidence that produced a horst‐and‐graben basin during the early stages of rifting of a volcanic arc along the eastern margin of Eurasia. These events occurred from 22.0 to 16.8 Ma before and during the formation of the Sea of Japan.