Magnetostratigraphy of Mesozoic and Paleozoic Systems in Japan

日本中生代和古生代系统的磁性地层学

基本信息

批准号：
62420015
负责人：
KODAMA Kazuto
金额：
$ 18.88万
依托单位：
Kochi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1990
项目状态：
已结题

项目摘要

1. Equipment for paleomagnetic measurement : An automated superconducting rock-magnetometer (2G760R) was installed in 1987, which made it possible to measure extremely weak remnant magnetization of sedimentary rocks.2. Tertiary System in Hokkaido : A paleomagnetic study of the Tertiary deposits in central Hokkaido demonstrated that central Hokkaido had experienced a counter-clockwise (CCW) tectonic rotation by 90^O about the vertical axis during the period between late Cretaceous and early Tertiary and, afterwards, suffered a clockwise (CW) rotation by 60^O during the middle Miocene.3. Tertiary System in south Kyushu : Paleomagnetic studies of the Miocene deposits in Tanegashima Island and Nichinan district in south Kyushu indicated that a CCW rotation by about 30^O had taken place in south Kyushu during the last 5 Ma. This suggests that south Kyushu is an independent tectonic unit which does not belong to the Southwest Japan block.4. Cretaceous System in Hokkaido : A reversed polarity zone, correlatable to chron 33r in the early Campanian, was found from the uppermost successions of the Cretaceous Ezo Group in central Hokkaido. All the lower successions showed normal polarity which can be assigned to the Cretaceous normal polarity superchron. Declinations were deflected westward, suggesting a CCW rotation for the area.5. Cretaceous System in southwest Japan : Magnetostratigraphic studies of the Upper Cretaceous Izumi Group in Shikoku and Awaji Islands identified three reversed polarity zones from the west of Matsuyama City, eastern Asan Mountains, and southern Awaji Island. They are correlatable to chrons 33r, 32r, and subchron 32.1r in the latest Cretaceous, respectively. The estimated sedimentation rate of the Izumi Group is extremely high, as much as 0.7 to 1 cm/yr.

1。古磁测量的设备：1987年安装了自动超导岩石磁铁计（2G760R），这使得可以测量对沉积岩的极弱的残余磁化。2。北海道的三级系统：北海道中部第三纪沉积物的一项古磁研究表明，北海道中部在晚期和早期的第三次和后期的垂直轴上逆时针旋转逆时针（CCW）构造旋转（CCW）构成旋转。九州南部的三级系统：对南蓝岛塔尼加岛岛和尼希南地区的中新世沉积物的古磁研究表明，在最后5 mA期间，在南蓝岛进行了大约30^o的CCW旋转。这表明South Kyushu是一个独立的构造单位，不属于西南日本区。4。北海道的白垩纪系统：从早期坎帕尼亚人的Chron 33R相关的反向极性区是从北海道中部的白垩纪Ezo Group的最高继承中发现的。所有较低的演替均显示出正常的极性，可以分配给白垩纪正常极性超沿着极性。向西偏转偏斜，表明该地区的CCW旋转5。日本西南部的白垩纪系统：Shikoku和Awaji群岛上白垩纪izumi Group的磁层学研究确定了三个反向极性区，来自马苏山城，东部山脉东部山脉和南部Awaji岛的西部。它们分别与最新白垩纪的Chrons 33R，32R和Subchron 32.1R相关。 Izumi组的估计沉积速率极高，高达0.7至1 cm/yr。