论文部分内容阅读
晚奥陶世赫南特冰期是地球历史上最重要的冰川事件之一,宜昌王家湾剖面作为奥陶系赫南特阶GSSP完整地记录了奥陶纪末期生物绝灭和环境变化事件.对王家湾小河边剖面(GSSP以南180m小河边)奥陶系-志留系界线地层及其碳氧稳定同位素组成进行了高分辨率研究.其中观音桥层主体为一套厚度小于30cm的泥质灰岩,保存有丰富的赫南特贝动物群化石记录,下伏上奥陶统五峰组笔石页岩,上覆下志留统(兰多维列统)龙马溪组笔石页岩.高分辨率测试分析了其中厚约25cm的观音桥层碳、氧稳定同位素组成,发现δ13Ccarb呈现出一次明显的负偏移趋势,在其上部达到最低值-12.8‰,是目前全球该层段无机碳同位素报道的最低值.认为这一明显的δ13Ccarb负偏事件指示了观音桥层沉积环境的突然变化,反映在冰盛期海平面下降时扬子海溶解无机碳库(DIC库)中加入了大量额外轻碳(12C)组份,其来源可能与海底甲烷有氧及厌氧氧化(AOM)或有机质有氧及厌氧氧化过程有关.
Late Ordovician Hernantean Ice Age is one of the most important glacial events in the history of the earth. The Wangjiawan section of Yichang has completely recorded the extinction and environmental change events of the Late Ordovician as the Ordovician Hernández-GSSP. The Xiaohebian section (180m small stream to the south of the GSSP) high-resolution study of Ordovician-Silurian boundary stratigraphy and its carbon-oxygen stable isotope composition, in which the main body of the Guanyin Bridge is a set of shale with a thickness less than 30cm Limestone is rich in fossil record of Hernantube fauna, underlying penolith shale of the Upper Ordovician Wufeng Formation overlying the Longmaxi Formation penolith shale of the Upper Silurian The resolution test analyzed the carbon and oxygen stable isotopic composition of the Guanyin Bridge with a thickness of about 25 cm. It was found that the δ13Ccarb exhibited a clear negative migration trend, reaching a minimum value of -12.8 ‰ at the top, which is the current global inorganic carbon The lowest δ13Ccarb negative event is believed to indicate a sudden change in the depositional environment at the Guanyin Bridge, reflecting the significant addition of DIC to the Yangtze Sea Dissolved Inorganic Carbon Pool (DIC) at sea level during the ice age Light carbon (12C) components , The origin of which may be related to the aerobic and anaerobic oxidation of seafloor methane (AOM) or the aerobic and anaerobic oxidation of organic matter.