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| 冲绳海槽北部表层沉积物中底栖有孔虫分布及其与海洋环境的关系 |
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向 荣1,2, 李铁刚1, 杨作升2, 阎 军1
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1.中国科学院海洋研究所;2.中国海洋大学海洋地球科学学院
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| 摘要: |
| 对1999年6月采自冲绳海槽北部的62个表层沉积物样品进行了底栖有孔虫分析。研究表明, 该区属种多为中外陆架和上部陆坡常见底栖有孔虫, 其中Cibicides pseudoungerianus在研究区域内广泛分布。底栖有孔虫群落明显受研究区水团的制约, 该区底栖有孔虫Q型因子分析反映的4个组合分别对应不同的水团影响: 组合1以Cibicides pseudoungerianus、Uvigerina sp.、Ammonia ketienziensis、Textularia pseudocarinata为主, 代表陆架混合水团影响环境；组合2以Uvigerina peregrina、Bulimina mexicana、Bulimina submarginata、Globocassidulina subglobosa为主, 代表黑潮暖流中层水影响下的环境；组合3以喜营养分子Bulimina marginata和Bolivina robusta为主, 代表冷涡沉积和上升流沉积区的环境；组合4以Cibicides pseudoungerianus、Globocassidulina subglobosa为主, 代表了对马暖流水团影响下的环境, 其中水团的氧含量水平和营养状况是影响底栖有孔虫组合变化的主要因素。底栖有孔虫的丰度从西往东依次出现两个丰度高值带, 一个位于研究区西部100—140m水深的陆架区, 另一个位于400—600m水深的上陆坡, 后者可能反映了冲绳海槽大陆坡普遍发育的陆坡上升流现象。
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| 关键词: 底栖有孔虫,冲绳海槽北部,海洋环境 |
| DOI：10.11693/hyhz200306012012 |
| 分类号: |
| 基金项目:国家自然科学基金项目,40176019号、40206007号;中国科学院知识创新工程资助项目,KZCX3-Sh7-220号及青岛海洋大学博士后资助项目,2002—2003 |
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| DISTRIBUTION OF BENTHIC FORAMINIFERA IN SURFICIAL SEDIMENTS FROM THE NORTHERN OKINAWA TROUGH AND ITS RELATION TO MARINE ENVIRONMENT |
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XIANG Rong1,2, LI Tie-Gang1, YANG Zuo-Sheng2, YAN Jun1
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1.Institute of Oceanology, The Chinese Academy of Sciences;2.College of Geosciences, Ocean University of China
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| Abstract: |
| An understanding of present-day benthic foraminifera are important in the reconstruction of marine paleoenvironment. In this paper, 62 surficial sediment samples obtained from the northern Okinawa Trough in June 1999 were selected to study the distribution of benthic foraminifera and its relation to the modern marine environment. The samples were treated with standard micropaleontology method: around 30g dry sediment per sample were dispersed in distilled water and washed through a 63μm mesh, to collect and count the benthic foraminifera from the size fraction of > 150μm; when necessary, sample were split to yield a sub-sample containing at least 300 specimens, with an average counted number of benthic foraminifera per sample being 322, and a total of 125 genera including 318 species or subspecies were identified.
There are 26 predominant species/genera with an average percentage of >1% of the total benthic foraminifera group, including Cibicides pseudoungerianus, 12.0%; Bulimina marginata, 4.9%; Textularia pseudocarinata, 3.7%; Ammonia ketienziensis, 3.0%; Hoeglundina elegans, 2.8%; Bolivina robusta, 2.6%; Elphidium advenum, 2.5%; Globocassidulina subglobosa, 2.3%; Heterolepa dutemplei, 2.1%; Discorbis spp., 2.1%; Hanzawaia nipponica, 2.1%; Bulimina submarginata, 1.8%; Gavelinopsis praegeri, 1.8%; Quinqueloculina subungeriana, 1.7%; Bolivina coechi, 1.6%; Gyroidina nipponica, 1.5%; Uvigerina peregrina, 1.5%; Sphaeroidina bulloides, 1.4%; Planulina wuellestorfi, 1.4%; Ammonia compressiuscula, 1.4%; Quinqueloculina sabulosa, 1.3%; Uvigerina vadescens, 1.1%; Cassidulina carinata, 1.0%; Lenticulina occidentalis, 1.0%; Verneuilina spp., 1.0% and Melonis spp., 1.0%. Among these Cibicides pseudoungerianus has a wide distribution in the study area.
67 species/genera with a relative abundance of exceeding 2% were chosen to carry out Q-mode factor analysis, and 4 varimax factors were obtained, which explain 82.2% of the total variance. The benthic foraminiferal fauna are affected by different water masses in the study area. The 4 benthic foraminiferal groups represented by 4 varimax factors correspond to different water masses. Group 1 is dominated by Cibicides pseudoungerianus, Uvigerina sp., Ammonia ketienziensis and Textularia pseudocarinata, which are distributed mainly on the continental shelf with water depth < 200m, representing an environment with high temperature and oxygen rich water mass, i.e., the continental shelf mixed water. Group 2 is composed mainly of cylindrical species Uvigerina peregrina, Bulimina mexicana, Bulimina submarginata and Globocassidulina subglobosa, which are distributed on the upper continental slope with water depth between 500—1000m, corresponding to the intermediate water mass of Kuroshio Current, the oxygen minimum zone of the Okinawa Trough. Group 3 is dominated by eutrophic species Bulimina marginata and Bolivina robusta, mainly distributed on the upper continental slope with water depth of 400—600m and the fine particle deposition area of the west continental shelf, corresponding probably to a gyro and upwelling deposition environment. Finally, Group 4 is composed mainly of Cibicides pseudoungerianus and Globocassidulina subglobosa, distributed mainly in the northern part of the study area; factor loadings show that this group is controlled by the continental shelf mixed water and Tsushima Warm Current water masses.
From the west to the east, benthic foraminifera show two high-abundance zones with abundance > 500 number of individuals per g, one being on the west continental shelf with water depth between 100—140m and the other being on the upper continental slope with water depth of 400—600m. The later high-abundance zone may correspond to the upwelling along the upper continental slope of the Okinawa Trough.
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| Key words: Benthic foraminifera, Northern Okinawa Trough, Marine environment |
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