The Permian Triassic boundary (PTB) and the lowest Triassic in the Yangtze region are considered to be the sediments of dysaeroxic and even anoxic environments, due to the dark thin bedded fine deposits, the highly developed parallel beddings with pyrites, the suppression of bio disturbance, and the monotonous fossils. However, the trace fossils there show a rather weak effect of the anoxic event. Meanwhile, the high resolution geochemical data are analyzed with 2 cm interval in the PTB and the lowest Triassic at the Majiashan Section, Chaohu, Anhui Province. The results show that the water depth of Chaohu region in the earliest Triassic was shallow, which might be a feature of the neritic environment. The high resolution geochemical proxies for anoxia have some contrary results. The geochemical data often indicate the dysaeroxic and even anoxic environments during that time, whereas other proxies (such as w (V)/ w (Cr), w (Ni)/ w (Co)) denote that they are normal marine sediments.
Peng Yuanqiao Tong Jinnan Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China Shi Guangrong School of Ecology and Environment, Deakin University, Rusden Campus, Clayton, Victoria 3168, Australia
With abundant deep-water upper Permian sediments, Guizhou is an ideal place for the research of radiolarian biostratigraphy of Upper Permian. The sections of Sidazhai and Lekang in southern Guizhou Province are studied. Lithology and biostratigraphy of the siliceous rock sequence of uppermost Permian in the two sections are introduced. Radiolarian assemblage zones, Neoalbaillella optima assemblage zone and Klaengspongus spinosus assemblage zone in ascending order are established for the topmost Permian of southern Guizhou. The Klaengspongus spinosus zone has been the topmost radiolarian assemblage zone of Permian, which is also correlated with former ones in a considerable depth.
The Middle Triassic was the great turning period of South China from marine sedimentary basins to continental deposits or erosion. This paper summarizes the distribution and variation of the stratigraphic sequences, lithofacies and biotas in various Middle Triassic depositional basins of South China. The close relationship between the biotic paleoecology and the lithofacies as well as the sedimentary facies, thus the paleogeography, is demonstrated. The process of the transition from the depositional paleogeography and its relation to the tectonic settings is concluded.
Tong Jinnan Liu Zhili Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China
