Reconstruction of Deep-Water Nitrogen Cycle during the Late Ediacaran in South China
The reconstruction of the paleo-ocean nitrogen cycle in geological history is helpful to understanding the REDOX state of the ocean at that time,whereas the study of the Late Ediacaran marine nitrogen cycle is relatively insufficient. Here we report detailed nitrogen isotope (δ15N) and organic carbon isotopic compositions (δ13Corg) from the Silikou section in northern Guangxi and the Shangdiping section in southeastern Guizhou Province. The results show that the average values of δ15N from the Silikou section and Shangdiping section are (1.6±2.0)‰ and (3.5±1.1)‰,respectively,both of which show a gradual decrease from old to new. The mean δ13Corg values of the two sections are (-30.0±1.4)‰ and (-30.6±1.4)‰,respectively. The relatively high δ15N values indicate that there was an aerobic nitrogen cycle coupled with nitrification and denitrification,and there was a stable marine nitrate reservoir in the Late Ediacaran. The gradual decrease from old to new in δ15N may result from the expansion of deep water anoxia in which denitrification and anammox can consume a large amount of NO3-and stimulate nitrogen fixation. Thus,the expansion of deep anoxic water column at the end of the Ediacaran may have exacerbated the extinction of the Ediacaran biota at～542 Ma.
nitrogen isotopeLate Ediacarandeep water faciesSouth Chinageochemistrystratigraphy
NETL
NSTL
万方数据
