藏北索县—巴青地区中侏罗世生物礁古生态学研究
摘要: 索县、巴青地区均位唐古拉山脉的南侧，属于羌塘地层区，其中，索县的桑卡拉佣组和巴青马如的布曲组中均发育有生物礁。造礁生物主要为六射珊瑚Schizosmilia、层孔虫Parastromatopora以及双壳类Liostrea。在分析造礁生物的个体生态特征基础上，根据研究区造礁生物类型及其组合特征，将生物礁划分为5个造礁群落，即Schizosmilia-Parastromatopora，Parastromatopora，Schizosmilia，Liostrea和Cyanobacteria-Liostrea造礁群落，并阐述了各群落的组成、结构与功能以及生态环境特征。根据群落在纵向上的组合与发育特征，分析了造礁群落的演化与海平面的变化特征，其中，Schizosmilia-Parastromatopora，Parastromatopora和Schizosmilia三个群落构成了索县地区造礁群落的演化序列，Liostrea和Cyanobacteria-Liostrea构成了巴青地区造礁群落的演化序列，造礁群落演化分析表明，群落演化表现为两种形式，第一种形式为群落演替，这种形式主要发育于索县桑卡拉佣组生物礁中；第二种形式为群落取代，这种形式主要发育于巴青布曲组生物礁中。最后，阐述了研究区的生物礁的发育特征与成礁方式，认为研究区主要成礁方式有造架作用、障积作用和黏结—障积作用，其中前两者主要体现于桑卡拉佣组生物礁中，后两种主要见于巴青布曲组生物礁中。
Study of Palaeoecology of Middle Jurassic Reefs in Suoxian and Baqing area of Northern Tibet
Abstract: Suoxian and Baqing county are located in the south side of Tangula mountain and belong to the Qiangtang stratigraphic area. However, Liuwan Formation of Suoxian and Buqu Formation of Baqing are especially characterized by a lot of organic reefs. Reef-building organisms are chiefly hexacorals Schizosmilia, Stromatoproids Parastromatopora and Bivalve Liostrea. The reef-building organisms mentioned above are majority preserved at the original growth state, which all require warm, clean and normal shallow water environment with abundant light and better circulation. Through the study of individual ecology and analysis of assembled of reef-building organisms, five reef-building communities are recognized, namely Schizosmilia-Parastromatopor，Parastromatopora， Schizosmilia，Liostrea and Cyanobacteria-Liostrea community. Among these five reef-building communities，First three communities formed reef-building community evolutionary sequence of Suoxian county area, while, Liostrea and Cyanobacteria-Liostrea community made up reef-building community evolutionary sequence of Baqing county area. Community evolution research indicates that it exists two kinds of community evolution in the studying areas, the first one is community succession that mainly developed in reefs of Liuwan Formation at Suoxian county, the second one is community replacement that developed in reefs of Buqu Formation in Baqing county. The developing characteristic of biological-baffling. Among these three reef-building, frame-making, baffling are developed in reefs of Liuwan Formation at Suoxian county, baffling and bind-baffling are seen in reefs of Buqu Formation in Baqing county. The authors hold that the existenc of reef communities is of great significance for further study of merging time of Bangongcuo-Nujiang River suture zone. The authors consider that oceanic crust subduction time of middle-east Bangongcuo-Nujiang River suture zone(ie. Suoxian and Baqing county region) should be in early age of Middle Jurassic or before the deposition of Liuwan Formation of Middle Jurassic. The existence of reef communities of Middle Jurassic showed that the study area may belong to a part of shallow continental shelf of the remaining back-arc basin after Bangongcuo-Nujiang River oceanic crust subduction.
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