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Modern analogue for the extinction and development of benthic foraminiferal fauna and its application to Neogene development

底栖有孔虫动物群灭绝和发展的现代模拟及其在新近纪发育中的应用

基本信息

批准号：
12640455
负责人：
NOMURA Ritsuo
金额：
$ 2.3万
依托单位：
Shimane University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

This study was aimed to obtain basic information from the recent marine environment to understand the geohistric events. The recent processes are important to consider the prehistoric processes of extinction and development of foraminiferal species and assemblage, because we have not still enough evidence to explain the processes. I focused on the drastic changes of foraminiferal assemblage with man-made dikes and water gate in Lake Nakaumi for land reclamation project. Foraminiferal species have changed their assemblage composition and particularly they became extinct in the enclosed area over 30 years. The benthic disappearance in the enclosed area is explained by the following three processes : (1) stop of saline water into brackish area, (2) temporal development of halocline and fertilized bottom sediments, (3) desalinitization of bottom water. The desalinitization of bottom water was associated with corrosive waters for calcareous grains such as foraminiferal tests. The other study indicates natural changes are also critical for the assemblage changes. Sea-level increase occurred in the 1940s and early 1950s, which enhanced the development of coastal species into brackish area and brackish species also invaded into lower saline area. The dredging of bottom sediments, as one of the human activities, accelerated upward flow of high saline bottom water.I have participated Ocean Drilling Program Leg 199 at the end of 2001 and I have a chance to observe the Paleocene/Eocene benthic extinction event. The processes of the abrupt extinction of foraminifera would be explained in comparison with above mentioned modern processes in later studies.

本研究旨在从近代海洋环境中获取基本信息，以了解地史事件。最近的过程对于考虑史前有孔虫物种和组合的灭绝和发展过程是重要的，因为我们仍然没有足够的证据来解释这些过程。在填海工程中，我利用人工堤坝和水门，集中研究了有孔虫组合的剧烈变化。近30年来，有孔虫物种的组合组成发生了变化，特别是在封闭地区灭绝。封垦区底栖生物消失的原因可归结为三个过程：(1)咸水停止进入半咸水区；(2)盐跃层和富营养化底沉积物的时间发育；(3)底水淡化。底水的脱盐与钙质颗粒的腐蚀性水有关，如有孔虫试验。另一项研究表明，自然变化也对组合变化至关重要。20世纪40年代和50年代初的海平面上升促进了沿海物种向咸淡水地区的发展，咸淡水物种也向低咸淡水地区入侵。海底沉积物的疏浚作为人类活动之一，加速了高含盐海底水向上流动。我在2001年底参加了Ocean Drilling Program Leg 199，我有机会观察到古新世/始新世底栖生物灭绝事件。有孔虫突然灭绝的过程将在以后的研究中与上述现代过程相比较加以解释。