报告题目: Early Triassic hothouse conditions limited marine productivity
报告人: Stephen Grasby教授
报告人单位: 加拿大地质调查局
报告时间: 2023年9月18日下午 15:00-17:00
报告地点: 北京大学逸夫二楼东连廊106会议室
Stephen Grasby
The Early Triassic represents a period of prolonged recovery following the most severe extinction of the Phanerozoic. Records show this to be a period of extremely high global temperatures, likely driven by Siberian Traps eruption induced global warming. How this hothouse impacted marine ecosystems and prolonged the recovery process remains uncertain. Across northwestern Pangea, Early Triassic marine sediments are characterized by low organic matter content, despite recurrent anoxia which would create conditions more suitable for preservation, and being located on the western continental margins were the majority of primary productivity in the Panthalassa Ocean would occur. Geochemical proxies suggest the paucity of organic matter reflects a productivity collapse rather than changes in preservation. Nitrogen isotopes show a progressive negative shift starting at the Permian/Triassic extinction and continuing through to the Smithian, indicating progressively growing nutrient limitation. High ocean temperatures likely deepened the thermocline, limiting nutrient recycling and upwelling into the photic zone driving nutrient stress. Finally ocean cooling in the Anisian is marked by widespread deposition of organic rich black shales and return of N isotopes to values consistent with active nutrient upwelling. A hyperthermal driven nutrient-limited Early Triassic ocean was likely a key inhibiter of marine recovery.
Stephen Grasby简介
Since completion of his PhD Dr Grasby has worked as a Research Scientist at the Geological Survey of Canada as well as an Adjunct Professor at the University of Calgary. His work has focused on the causes of mass extinctions through the Phanerozoic, with field and lab based studies. Working mostly in the Canadian High Arctic he has also worked in locations around the world studying various extinction boundaries and oceanic anoxic events. In recognition of his research he was awarded the Queen Elisabeth the Second Diamond Jubilee Medal.
