Biostratigraphy and Chemostratigraphy Across the Lower Kellwasser Boundary in Laye Section, Guizhou Province

CHANG Jieqiong1, BAI Zhiqiang1, LI Yukun2, GUO Jianxiang3, PENG Yongbo4, SHEN Bing1,†

1. The Key Laboratory of Orogenic Belts and Crustal Evolution (MOE), School of Earth and Space Sciences, Peking University, Beijing 100871; 2. Guangxi Geological Survey, Naning 530023; 3. Geology Team No. 4 of Guangxi, Naning 530033; 4. Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803; † Corresponding author, E-mail: bingshen@pku.edu.cn

Abstract In order to study biostratigraphy and chemical stratigraphy during the Lower Kellwasser event, high resolution conodonts research and chemostratigraphic framework were carried out. The data reveals that the inorganic and organic carbon isotope have a significant positive excursion at the bottom of the Laye section. It is considered that the sample LY-8 is consistent with the Lower Kellwasser boundary. The main reason for the change of carbon isotope in this area is the increase of organic carbon burial, which is caused by the increase of marine primary productivity and anoxia environment possibly. Key words Lower Kellwasser boundary; conodont; carbon isotope; organic carbon burial; marine primary productivity

1850 年, Roemer[1]首次描述德国中部 Harz 山脉 Kellwasser 山谷中的黑色沥青质石灰岩和页岩层, 并命名为“Kellwasser-kalk” (Kellwasser 边界)。‒法门期之交,经过几十年的研究, 人们发现这种黑色灰岩和页岩层形成于晚泥盆世弗拉期 且广布于中欧和西欧, 在北美、中亚和北非也偶有发现[2],形成的原因是缺氧事件。后来, 学者们将这种特殊

的岩层与五大生物灭绝事件中的晚泥盆世弗拉‒法门(F-F)灭绝事件联系起来, 将 F-F 事件称为 Kellwasser事件[34]。“Kellwasser 岩相”在欧洲和北非等地表现为各种岩性(可能是页岩、含头足类灰岩)的沉积岩中夹的两层黑色沥青质(富含有机质)灰岩或泥页岩, 其中一层位于上 Pa. rhenana 带顶部(下Kellwasser 事件), 另一层位于 Pa. linguiformis 带与