权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

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钻井船JOIDES resolution从北太平洋的深海海底沉积物中收集的。沿中纬度地区从西向东选择三个区域；三陆崎代表西部边界流区，加利福尼亚边缘代表东部地区，沙斯基隆起代表连接其他地区。我分析了中新世至更新世期间由微化石和碎屑颗粒组成的海洋沉积物，并根据形貌比较了三个地区硅藻频率的地层分布。圆形硅藻是三陆崎海域的优势种，但沙斯基海涌中有许多圆形的上升流类型。圆形型、上升流型和船形型三个分类群轮流占据加利福尼亚边缘优势种的位置。环境的稳定延续带来了圆形的形状……在三陆町水域中更有规律的卓越水平。另一方面，加利福尼亚边缘给出了沿海上升流零星发生的多变环境。虽然3个地区化石组合的组成和频率不同，但变化的外在表现在增减上是相似的。虽然各地区之间的距离相当远，但它们所监测到的北太平洋同一洋流的影响似乎是长期的。在沙斯基隆起和加利福尼亚边缘，硅藻取代放射虫成为8 Ma个体数量的高峰。硅质微化石组合主要由硅藻和放射虫组成，在8 Ma之前发现的硅质微化石组合命名为组合1，在8 Ma之后发现的硅质微化石组合命名为组合2。据推测，8 Ma的微化石转变与印尼门户的关闭导致北太平洋从表面到底部的洋流系统发生了严格的变化相对应。在硅藻和放射虫的增减周期中，每个周期从3 Ma左右开始缩短，幅度变得剧烈。旋回变化边界将硅质组合细分为早期组合2a和晚期组合2b。从组合2a到组合2b的演替反映了3 Ma以来北半球冰川作用的增强。少