青森県・深浦—鮮参ヶ沢地域，前期中新世大戸瀬層のK-Ar年代と火山岩相
青森県・深浦—鮮参ヶ沢地域，前期中新世大戸瀬層のK-Ar年代と火山岩相
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青森县深浦—Sensingasawa地区早中新世大势组K-Ar年龄与火山岩性
DOI：
10.2465/ganko.93.207
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
健志 大口
中科院分区：
文献类型：
--
作者：
林田 信太郎;健志 大口
对日本东北部青森县藤仓-尾川地区中新世早中新世欧迪格组火山岩进行了K-Ar测年，以确定早中新世早中新世的海侵时代，并明确了这些地区的Nishikurosawa海侵之前的海洋沉积物的空间分布(&Gt；20 Ma)，发现于秋田县小贺半岛。大田组被划分为三个岩段：尾川地区(平山和上村，1985)的清高泽安山岩、Azumagawa流纹岩和Kohamadatezawa安山岩，它们对应于藤村地区(Moritani，1968)的下部、中部(Sawabe火山岩)和上部(Moritani，1968)。初步的相分析表明，这些火山岩序列是在近岸环境中沉积的。萨瓦贝火山岩中的高铝橄榄辉石安山岩的年龄为20.0±1.0 Ma，与Fukudome等报道的20.6±2.0 Ma的年龄相吻合。(1990)，清高泽安山段上部的碱性橄榄石玄武岩年龄为19.4±1.1 Ma。由于海相软体动物化石是由平山和上村(1985)在清高泽安山段中部发现的，该段上部的年龄限制了艾治泽地区早中新世海侵的海相沉积年龄上限。此外，K-Ar年龄研究的结果表明，该地区的海洋沉积物与欧加半岛的沉积物具有很好的相关性。
K-Ar dating was performed for volcanic rocks from the early Miocene Odose Formation, Fukaura-Ajigasawa area, Aomori Prefecture in northeast Japan to determine the age of the early Miocene transgression, prior to the Nishikurosawa transgression of these area, and to make clear an spatial distribution of marine sediments (>20 Ma) found in the Oga Peninsula, Akita Prefecture. The Odose Formation is divided into three members: the Kiyotakizawa Andesite, the Azumagawa Rhyolite and the Kohamadatezawa Andesite Members in ascending order in the Ajigasawa area (Hirayama and Uemura, 1985), which are corresponded to the lower, middle(Sawabe volcanic rock) and upper part in the Fukaura area (Moritani, 1968). Preliminary facies analysis of the Sawabe volcanic rock and the upper part of the Kiyotakizawa Andesite Member of the Odose Formation indicates that these volcanic sequences were deposited in the near shore environment, evidenced by the presence of sandstone with hammocky cross stratification and intrusion of spiracle into aa lava flows. A high alumina olivine pyroxene andesite of the Sawabe volcanic rock has an age of 20.0±1.0 Ma which coincide with the age of 20.6±2.0 Ma reported by Fukudome et al. (1990), and an alkali olivine basalt from the upper part of the Kiyotakizawa Andesite Member shows 19.4±1.1 Ma. Because marine molluscan fossils were found by Hirayama and Uemura (1985) from the middle part of the Kiyotakizawa Andesite Member, the age from the upper part of the member constrains the upper limit a marine sediment age by early Miocene transgression in Ajigasawa area. Furthermore, the result of the present K-Ar age study indicates that the marine sediments in the area are well correlate with the sediments in the Oga Peninsula.