FREQUENCY, AMPLITUDE, AND PATTERN OF SEA LEVEL CHANGES IN DEVONIAN IN LONGMEN MOUNTAINS, WESTERN YANGTZE
Li Xianghui, Liu Wenjun, Zheng Rongcai (Chengdu University of Technology, China)
Eighteen cycles of sea level rising and falling are recognized in Devonian in Longmen Mountains , western Yangtze. They are superposed to be three para 2nd order cycles and one 2nd order cycle, in which four types of frequency (Fm) - amplitude (Am) of sea level rising and falling can be distinguished as low Fm - low Am, high Fm - low Am, low Fm - high Am, and high Fm - high Am. The Devonian relative sea level changes in time gradient, the characteristic of undulation from gentle rising and long duration to stable falling and short duration are consistent with those all over the world at the same time, although the stratigraphic horizon of the highest and lowest stands are different. The highest stand horizon in Longmen Mountains, the Tuqiaozi Formation, is in the mid lower asymmetricus zone in the early Frasnian that is lower than that in western Qingling Mountain, Euramerica , and higher than that in southwestern Siberia; the lowest stand horizon, the top of Pingyipu Formation, is roughly in the mid upper kindlei zone in Pragian which is earlier than that in Euramerica , Siberia and South China. At the end of the paper, some problems and significances on the pattern, frequency, amplitude and benthic water depth curve are discussed.