西藏南部放射虫微体古生物研究进展

PROGRESS IN RADIOLARIAN MICROPALEONTOLOGICAL STUDIES IN SOUTHERN TIBET

西藏南部的雅鲁藏布蛇绿岩带以及该带之南的沉积地层带 (特提斯沉积区、北喜马拉雅亚区 )中广泛发育着大量含放射虫地层。放射虫研究在确定该区蛇绿岩的形成时代、解释造山带复杂的地层层序以及揭示印度板块与欧亚板块在古近纪碰撞之前的古海洋盆地的演化历史等方面发挥了重要作用。根据已发表的文献以及我们正在进行中的初步成果显示 ,藏南地区的含放射虫地层的时代分布为中三叠世 (安尼期 )至晚白垩世 (土仑期 )。这些地层的岩性包括硅质岩、硅质泥岩、凝灰质细碎屑岩和泥晶灰岩等。尽管藏南的放射虫研究已取得一些成果 ,但系统的放射虫研究与地层研究仍然有待于进一步深入开展。

Radiolarianbearing strata are widespread in the Yarlung Zangbo Ophiolitic Complex and in the stratigraphic belt immediately to the south which is referred to as the “Northern Himalayan Subprovince of Tethyan Strata” in southern Tibet. Radiolaria have played an important role in determining formation time of the ophiolites and in interpreting the complicated stratigraphy and evolutionary history of the oceanic basins before the Indian block collided with the southern margin of the Eurasian plate in early Cenozoic time. A few radiolarian studies from this region have been published. According to available published data and our ongoing investigation in the region, radiolarianbearing strata here range from Middle Triassic(Anisian) or earlier to Late Cretaceous(Turonian) in age. Sedimentary lithologies include chert, siliceous mudstone, tuffaceous fineclastic rock, and micritic limestone. A systematic analysis of the ratiolarian fossils and their biostratigraphic implications in southern Tibet is yet to be carried out.