西沙群岛永乐环礁琛科2井的珊瑚藻组成及其水深指示意义

THE COMPOSITION OF CORALLINE ALGAE FROM WELL CHENKE-2 IN XISHA ISLANDS SOUTH CHINA SEA,CHINA AND ITS IMPLICATION ON THE WATER DEPTH

本文对中国南海西沙群岛琛科2井中新世以来的珊瑚藻组成进行了初步研究,共识别出3科4亚科11属,包括石叶藻亚科石叶藻属(Lithophyllum)和蟹手藻属(Amphiroa);宽珊藻亚科似绵藻属(Spongites)、新角石藻属(Neogoniolithon)和石孔藻属(Lithoporella);珊瑚藻亚科让氏藻属(Jania)和珊瑚藻属(Corallina),无节珊瑚藻亚科中叶藻属(Mesophyllum)、奇石藻属(Aethesolithon)和石枝藻属(Lithothamnion);孢石藻亚科孢石藻属(Sporolithon)。并得出以下认识:(1)珊瑚藻类群,指示浅水环境;无节珊瑚藻类群,指示深水环境;宽珊藻类群,指示最浅水环境;石叶藻类群,指示浅水环境。(2)琛科2井自下而上分为7个组合:让氏藻属-珊瑚藻属-石孔藻属组合;奇石藻属组合;中叶藻属-石枝藻属组合;似绵藻属组合;石枝藻属组合;中叶藻属-石叶藻属组合;石孔藻属-石叶藻属组合。(3)878.21 m的珊瑚礁碳酸盐岩心,以309.00-312.00 m为界,分为两个大沉积旋回。第一个沉积旋回珊瑚藻组合经历了具关节的珊瑚藻属-让氏藻属-石孔藻属组合,奇石藻属组合,石枝藻属-中叶藻属组合,似绵藻属组合的变化,反映了水体由浅加深,到最后又变浅的过程;第二个沉积旋回珊瑚藻组合出现了似绵藻藻属组合,石枝藻组合,中叶藻属-石叶藻属-石孔藻属组合,石叶藻属组合的变化,反映了水体由浅加深再变浅的珊瑚藻组合的相应变化。

The coralline algae recognized in well Chenke-2, Xisha Islands since the Miocene include 11 genus in 3 families, 4 subfamilies. They are Lithophylloideae Lithophyllum Amphiroa; Mastophoroideae Spongites, Neogoniolithon and Lithoporella ; Corallinoideae Jania and Corallina, Melobesiodideae Mesoph yllum, Aethesolithon and Lithothamnion ~ and Sporolithaceae Sporolithon. The algae categories were considered to be linked to different water depth. Corallinoid indicates a shallow water environment; Melobesioid indicates a deep water environment; Mastophoroid indicates a most shallow water environment; and Lithophylloid indicates a shallow water environment. There are 7 coralline algae assemblages identified from bottom to top. They are Jania-Corallina Lithopoerlla assemblage, Aethesolithon assemblage, Mesophyllurn：Lithoth- amnium assemblage, S[ongites assemblage, Lithotharnnium assemblage, Mesojhyllurn-Lithotharnniurn assemblage and Lithopoerlla-Lithophyllum assemblage. The 878. 2Ira-thick coral reef carbonate sequence can be divided into two large sedi mentary cycles with aboundary at 309--312. In the lower sedimentary cycle, coralline algae bottom-up experienced Jania- Corallina-Lithopoerlla assemblage, Aethesolithon assemblage, MesophyZlurn：Lithothamniurn assemblage and S[ongites as- semblage （Corallinoid-Melobesiodid-Mastophoroid）, reflecting the process of water depth of shallow-deep-shallow. In the upper sedimentary cycle, Lithothamnium assemblage, MesophyllurnLithotharnniurn assemblage, Lithopoerlla-LithoDhyl- lurn assemblage （Melobesiodid-Lithophylloid） were occured from bottom to top, reflects another the process of water depth of shallow-deep-shallow.