K-Ar ages of Miocene volcanic rocks from western Tsugaru, Aomori prefecture, Northeast Japan
K-Ar ages of Miocene volcanic rocks from western Tsugaru, Aomori prefecture, Northeast Japan
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日本东北部青森县津轻西部中新世火山岩的 K-Ar 年龄
DOI：
10.3720/japt.68.2-3_191
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
Takeyoshi Yoshida
中科院分区：
文献类型：
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作者：
H. Hoshi;Mutsumu Ishii;Takeyoshi Yoshida
对采自青森县西部津轻地区奥多寺组的5个火山岩样品进行了K-Ar年龄测定。对不同地层位置的熔岩流进行了取样。用同位素稀释法测定了早中新世至中中新世的年龄，年龄范围为20 ~ 14 Ma。3个年龄测定值（19.7·}0.5 Ma、19.1·}0.5 Ma、18.2·}0.5 Ma）与地层一致，是可靠的，而另外2个年龄测定值（14.4·}0.4 Ma、16.9·}0.5 Ma）则被认为受到年龄降低的影响。根据我们的研究结果和现有的放射性年龄，奥多寺组被指定为上下中新统。这一地层的火山活动开始于约20 Ma，停止于约18 Ma;可能与古地磁学上认为的日本东北部逆时针旋转（与日本海的开放有关）是同时代的。
K-Ar dating was carried out on groundmass fractions of five volcanic rock samples collected from the Odose Formation in the western Tsugaru district, Aomori Prefecture. Lava flows at different stratigraphic positions were sampled. Early to Middle Miocene ages ranging from about 20 Ma to 14 Ma were determined by the isotope dilution method. Three age determinations (19.7•}0.5 Ma, 19.1•}0.5 Ma, 18.2•}0.5 Ma) are reliable as they are concordant with stratigraphy, whereas another two (14.4•}0.4 Ma, 16.9•}0.5 Ma) are thought to have been affected by age lowering. On the basis of our results and existing radiometric ages, the Odose Formation is assigned to the upper Lower Miocene. The volcanic activity of this formation began about 20 Ma and ceased about 18 Ma; probably it was coeval with the paleomagnetically suggested counterclockwise rotation of Northeast Japan associated with the opening of the Japan Sea.
DOI：
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发表时间：
1992
期刊：
--
影响因子：
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作者：
I. Kaneoka;Y. Takigami;N. Takaoka;S. Yamashita;K. Tamaki
通讯作者：
I. Kaneoka;Y. Takigami;N. Takaoka;S. Yamashita;K. Tamaki