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Paleoceanographic reconstruction in the eastern and western boundary current areas of the North Pacific Ocean by using diatom fossils.

利用硅藻化石重建北太平洋东西边界流区的古海洋学.

基本信息

批准号：
15540445
负责人：
MARUYAMA Toshiaki
金额：
$ 2.43万
依托单位：
Yamagata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540445/
关键词：
diatom Pacific paleoceanograph upwelling Cenozoic 新代三紀新第三紀新世代

项目摘要

All materials treated in this study were collected from deep-sea floor sediments in the North Pacific Ocean via the dill ship JOIDES resolution assigned to the Ocean Drilling Program. Three areas along the middle latitudes are chosen from west to east ; Sanriku-oki representing the western boundary current area, California margin from the eastern area, and Shatsky Rise for connecting with the others. I analyzed marine deposits consisting of microfossils and clastic particles from Miocene through Pleistocene Epoch, and I compared the stratigraphic distributions of diatom frequency based on morphology among three areas.Round shape diatoms became dominant species in the Sanriku-oki offing, but there were many upwelling current types with round shape in Shatsky Rise. Three taxon groups involving round shape, upwelling current type and boat-shaped type took turns at occupying the position of dominant species off California margin. Stable continuation of environments brought round shapes to … More a level of regular excellence in Sanriku-oki offing. On the other hand, changeable environments in which coastal upwelling current happened sporadically were given off California margin. Although composition and frequency of fossil assemblages are different from each other, the outward appearance of change is similar in increase or decrease among three areas. There was a considerable distance between areas, however, it seems that their areas monitored influence of the same current in the North Pacific Ocean through time.On both of Shatsky Rise and California margin, diatoms replaced radiolarians as the summit of individual number at 8 Ma. Siliceous microfossil assemblages consist mainly of diatoms and radiolarians, and those found before 8 Ma are named Assemblage-1, those after 8 Ma are called Assemblage-2, respectively. It is supposed that the microfossil transformation at 8 Ma corresponds with a strict change in ocean current system supervising from the surface to the bottom of the North Pacific due to closing of the Indonesian Gateway. In the cycle of increase or decrease of both diatoms and radiolarians, each period shortens from about 3 Ma and the amplitude got violent. The boundary between cycle changes subdivides siliceous assemblages into the early Assemblage-2a and the late Assemblage-2b. It is thought that a succession from Assemblage-2a through Assemblage-2b reflects reinforcement for the Northern Hemisphere glaciation becoming stronger from 3 Ma. Less

本研究中处理的所有材料都是通过分配给海洋钻探计划的DILL船JOIDES RESOLUTION从北太平洋的深海海底沉积物中收集的。从西到东选择了中纬度的三个区域：三陆-奥基代表西部边界流区，加利福尼亚州边缘从东部地区，沙茨基隆起连接其他地区。分析了中新世至更新世由微体化石和碎屑颗粒组成的海相沉积，比较了三个海区硅藻分布的形态特征，发现圆形硅藻是三陆海域的优势种，但沙茨基隆起有许多圆形的上升流类型。圆型、上升流型和船型3个类群轮流占据加州边缘优势种的位置。环境的稳定延续为…带来了圆形形状更多的是在三陆-木的常规卓越水平。另一方面，加州边缘提供了零星发生沿岸上升流的多变环境。尽管化石组合的组成和频率不同，但三个地区变化的外观是相似的，是增减的。在沙茨基隆起和加利福尼亚边缘，硅藻在8 Ma时取代放射虫成为个体数量的顶峰。硅质微体化石组合主要由硅藻和放射虫组成，在8 Ma之前发现的称为组合1，在8 Ma以后发现的称为组合2。据推测，8 Ma以来的微化石转变对应着由于印度尼西亚门的关闭，北太平洋从表层到底部的洋流系统发生了严格的变化。在硅藻和放射虫的增减周期中，每个周期都从3 Ma左右缩短，幅度变大。旋回变化之间的边界将硅质组合细分为早期组合-2a和晚期组合-2b。从-2a组合到-2b组合的序列被认为反映了北半球冰川从3 Ma开始变得更强的加固作用。较少