| 摘要: |
| 于1994年春在杭州西湖东北面、西面及湖中心小瀛洲3个钻孔共取了70号岩芯样，经浮选、筛选，以显微镜检鉴定化石藻种，并分析其垂直分布，从而探讨西湖的形成历史。西湖自晚更新世以来的6个化石藻带由下而上依次为：轮藻带、微红金颗藻-近缘针杆藻-条纹小环藻带、圆筛藻带、圆筛藻-近缘针杆藻-微红金颗藻带、桥穹藻-异极藻-短缝藻带和水花束丝藻带，从而反映了西湖的6个发育时期：淡水古湖沼期、淡咸水过渡期、海湾期、泻湖期、淡水西湖沼泽期和淡水西湖富营养化期。从淡水轮藻组成的古湖沼期的存在，提出西湖起始于淡水湖沼，而不是以泻湖、海湾等海相生境开始的。 |
| 关键词: 化石藻 硅藻 淡水藻 半咸水藻 海藻 |
| DOI： |
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| 基金项目:国家自然科学基金资助项目，39370140号 |
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| PROBING INTO THE HISTORY OF THE WEST LAKE, HANGZHOU, BASED UPON THE VERTICAL DISTRIBUTION OF ALGAL MICROFOSSILS |
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XIANG Si-duan1, ZHAO Jian-kang2, ZHOU Hong1, WANG Jiang-yi1
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1.College of Life Science,Zhejiang University,Hangzhou 310012;2.The Geological Environmental Monitoring Station of Zhjiang,Hangzhou,310007
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| Abstract: |
| In spring 1994, 70 sediment samples from 3 cores, collected from the northeastern shore (X2), western shore (X2) and Xiaoyingzhou (No. 6) of the West Lake were analyzed. 63 species of microfossil algae are found, including 79% of diatoms; these algal microfossils made up 18 assemblages. From bottom to top, the core X1 is divided into six algal zones according to indicator species of algal assemblages: I. Chara zone: -32–-29m; II. Chrysococcus rubescedssynedra affinis–Cyclotella striata zone: -29.0–-24m, characterized by coexistence of fresh water algae, brackish water algae and marine algae; III. Coscinodiscus zone: -24–-13m, marine algae zone; IV. Coscinodiscus–Synedra affainis–Chrysococcus rubescens zone: -13–-7m, coexistence of marine, brackish and fresh-water algae; V. Cymbella–Gomphonema–Ennotia zone: -7–-4m, freshwater epiphytic algae zone; VI. Aphanizomenon zone: -4m and above. These zones indicates 6 developing stages of the lake i.e. paleopond stage, fresh water to marine transitional stage, bay stage, lagoon stage, fresh water West Lake bog stage, and a eutrophic stage of fresh water.
The algal zones in cores X2 and NO. 6 are lack of Zones I, II. Thus, paleopond stage and fresh water to marine transitional stage are absent at these two sites; only 4 developing stages exist.
The existence of the paleopond stage shows that, around 10 thousand years age, the West Lake originated from a fresh water pond, instead of a lagoon or embayment. |
| Key words: Fossil algae, Diatom, Fresh water algae, Brackish water algae, Marine algae |
