华南埃迪卡拉系年代地层学

A series of biological and environmental events occurred during the Ediacaran period (635-541 Ma). Owning to lack of reliable isotopic age constraints, depositional ages of some key events remain uncertain, which is unfavorable for ascertaining the causal relationships of biological and environmental events. Meanwhile, it hampered regional and global stratigraphic correlation. Such biological and environmental events are also recorded in the Ediacaran strata of South China. Among these strata, the black shale and intercalated volcanic tuff/tuffaceous siltstone permit us to carry out monazite and zircon U-Pb/Pb-Pb dating analyses. This proposal aims to, by using these dating methods, ascertain the causal relationships of biological and environmental events. In doing so, we are trying to conduct regional and global correlation of these events and make clear their order and causal relationships.

新元古代埃迪卡拉纪（635-541 Ma）时地球表面发了一系列重大生物事件和环境事件。然而，由于缺少可靠的同位素年龄制约，一些关键生物事件和环境事件的年龄还不确定，因此很难理清这些事件的因果关系，同时也妨碍了区域和全球地层对比。这些事件在我国华南埃迪卡拉纪地层中都有很好的记录。这段时期沉积的黑色页岩和夹层火山凝灰岩/凝灰质粉砂岩对于开展黑色页岩中独居石和火山凝灰岩/凝灰质粉砂岩锆石U-Pb/Pb-Pb 定年提供了有利条件。本项目拟通过这些测年方法来厘定这一时期关键生物事件和环境事件发生的时间，以此来将这些事件进行区域和全球对比，进而理清这些事件发生的先后顺序和因果关系。

新元古代埃迪卡拉纪-寒武纪早期（635-520 Ma）地球表面发了一系列重大生物事件和环境事件。由于缺少可靠同位素年龄和化学地层数据的制约，很难理清这些事件的因果关系，也妨碍了区域和全球地层对比。该项目通过对我国华南埃迪卡拉系和下寒武统地层进行地质年代学和化学地层学研究，把瓮安生物群的产出时代限定在了ca. 609 Ma，把小壳化石、三叶虫化石和Ni-Mo-PGE 成矿层的产出时代限定在了532-527 Ma，否定了Ni-Mo-PGE 成矿层为前寒武纪-寒武纪过渡时期的边界层，解决了浅水相和深水相区域地层对比。提出扬子板块北缘南秦岭地区ca. 626 Ma岩浆作用是导致扬子地区出现碳同位素负漂移的直接原因。通过高分辨率化学地层研究，建立了区域化学地层对比，识别出了两次碳同位素负漂移，和冰川作用导致的海平面下降有关。另外，该项目还从华南成冰系和埃迪卡拉系地层中识别出了两类热液磷钇矿，其形成可能和武夷-云开造山运动有关。