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

The prosperity and decay and the three dimensional reconstruction of chemosynthetic autotrophic communities in shelf environments.

陆架环境化能合成自养群落的繁荣与衰败及其三维重建.

基本信息

批准号：
10440146
负责人：
MAJIMA Ryuichi
金额：
$ 7.55万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

The main results of this study can be divided into the following three parts.(1) A boring investigation, totally 100m in core length, for a cold-seep chemosynthetic community in the lower Plesitocene Koshiba Formation at Segami, Yokohama City indicates that it has about 40 m in height, normal for the bedding plane, and about 20 m in width, parallel for the bedding plane. The litho-facies of the core are of upward fining from mudstone, the upper part of the Ofuna Formation, to muddy sandstone, the lower part of the Koshiba Formation. This result evidently suggests that the seepage at Segami continued for a long period of time, and the community occurred in a regressive phase in the depositional cycle. The middle part of the core has a representative litho-facies, such as an oblique litho-boundary for the bedding plane, crashed shell fragments of large bivalves, probably Lucinoma sp., in several horizons, and a few scoria beds entirely replaced their matrix with white carbonates. These litho-facies suggest an explosive eruption of methane that has been considered to be a cause of pock marks observed on the present oceanic floor.(2) A Pleistocene, cold-seep chemosynthetic community is discovered from the Shintomi Town, Miyazaki Prefecture. This community is exposed in the range of 100m in N-S direction, 60m in E-W, and 10m in thickness, and occurs in the upward fining, regressive sequence.(3) Holocene concretions including Conchocele sp. and/or Calyptogena sp. are discovered from off Wakkanai City, Hokkaido. The depleted 13C of the carbonate cements of the concretions suggests that these communities were depended upon the methane seepage.

本研究的主要结果可以分为以下三个部分。(1)对横滨市世上更新统下段小芝组冷泉化能群落进行了100 m岩心钻探，结果表明，冷泉化能群落垂直于层理面，高约40 m，平行于层理面，宽约20 m。岩心的岩相从大船组上部的泥岩到小芝组下部的泥质砂岩呈向上变细的趋势。这一结果显然表明，濑上的渗漏持续了很长一段时间，该群落出现在沉积循环的海退阶段。岩芯中部具有代表性的岩相，如层面的倾斜岩石边界，大型双壳类的破碎贝壳碎片，可能是Lucinoma sp.，在几个层位中，一些火山渣床完全用白色碳酸盐代替了它们的基质。这些岩相表明甲烷的爆炸性喷发，被认为是在现在的海底观察到的麻点的原因。(2)在宫崎县新富町发现更新世冷泉化能群落。该群落出露范围为南北向100 m，东西向60 m，厚度10 m，呈向上变细、海退的层序。(3)在北海道若奈市近海发现了包括贝壳类（Conchocele sp.）和/或盖形类（Calyptogena sp.）在内的全新世结核。结核中碳酸盐胶结物的~（13）C亏损表明，这些生物群落依赖于甲烷渗漏。