摘要
测制了目前藏北地区最为完整的申扎扎扛古生界剖面,发现了早奥陶世阿雷尼格期的笔石动物群,确定该动物群属于西藏已知层位最低、时代最早的动物群,建立了下奥陶统扎扛组(O1z)。在下二叠统下拉组之上发现了一套逾2400m的白云质岩石,产Waagenophyllum-Liangshanophyllum-Lobatophyllum组合,时代为晚二叠世吴家坪期,并建立上二叠统木纠错组(P3m)。在冈底斯地区新发现印支期巨斑花岗闪长岩(锆石U-Pb年龄217Ma),提供了古冈底斯存在的重要信息。查明查藏错-申扎南北向裂陷带南北向长超过100km、宽6750～12500m,平面呈折线状;根据地质依据和沉积物定年研究,130ka以来裂陷盆地东西向扩张数率为北部51.9mm/a、南部94.2mm/a。
Through field investigation, the most complete Paleozoic section in northern Tibet was measured in the Zakang area, Xainza County, where the Early Ordovician Arenigian graptolite fauna was discovered. This fauna is the oldest one at the known lowest horizon in Tibet, so the authors establish the Lower Ordovician Zakang Formation (O1z). A sequence of dolomitic rocks over 2400 m thick was discovered above the Lower Permian Xiala Formation, in which the Waagenophyllum-Liangshanophyllum-Lobatophyllum assemblage was discovered; so its age is Early Permian Wujiapingian, and then the Upper Permian Mujiucuo Formation (P3m) was founded. Indosinian macrophyric granodiorite (single zircon age 217 Ma) was discovered in the Gangdise area, which implies that in the Gangdise area there is important information of the Indosinian movement and the old Gangdise. The N-S-trending Chazang Co-Xainza fault belt is >100 km long and 6750-12500 m wide and zigzag in plan view. Based on the geological evidence and dating of sediments the rate of E-W extension of the rift basin since 130 ka BP is 51.9 mm/a in the north and 94.2 mm/a in the south.
出处
《地质通报》
CAS
CSCD
北大核心
2004年第5期479-483,共5页
Geological Bulletin of China
基金
中国地质调查局青藏高原1:25万申扎县幅(H45C002004)地调项目成果。
