特提斯演化过程中火山活动对古、中生代之交的陆海生产者及其环境的影响

古生代与中生代之交既是地球历史演化过程的转折期，又是特提斯洋及其周边板块汇聚、大规模火山活动、最大生物灭绝和气候环境剧变等一系列地质事件集中爆发的关键时期，但是有关地球内部圈层演化和表层生物-环境演变之间的因果关系、具体机制和动力学过程还很不清楚，特别是对衔接深部过程与表层系统的食物链中能量“金字塔”底层的陆地植物和海洋生产者这一关键缺环还有待于深入。项目立足于特提斯地球动力系统重大研究计划，以位于古特提斯洋周缘地区不同沉积相区地层为研究对象，以火山作用为“抓手”，以陆地生态系统为连接桥梁，探究在古-中生代之交特提斯洋及周边板块汇聚和裂解过程中，地球内部圈层物质和能量释放对调控大气O2和CO2浓度的陆海生产者演变（如异化、特化、去生物地理区系化等）及其环境剧变（如毒化）的影响。该项目的实施为认识特提斯洋演化过程中地球内部和地球表层陆地和海洋系统的耦合关系提供研究范例。

The Paleozoic-Mesozoic transition was one of the most critical intervals in Earth history. It witnessed the formation of the supercontinent (Pangea), closure of the Paleo-Tethys ocean, large-scale volcanism (Siberian Traps Large Igneous Province; regional arc volcanism in the Tethyan region), transfer from cooling to warming climate and the largest mass extinction along with severe environmental perturbations both on land and in the ocean. These events were nearly synchronous, but their cause-and-effect relationships remain unclear. Key pieces of information are lacking: First, it`s unclear about the duration, frequency, and intense of the arc volcanisms near the Tethyan region; Second, little is known about the evolution of primary producers at the base of the food chain. Yet these producers were a significant factor in environmental perturbations (e.g., chemical weathering, anoxia, global warming); Third, it`s still unknown about the relationships among volcanisms near the Tethys, ecosystem perturbations on land, and the unstable marine ecosystem. In this proposal, as part of the “Major Research project on Tethys Geodynamic Systems”, we will investigate the biological and geochemical records of sediments (from the Late Permian Wuchiapingian Stage to the Middle Anisian Stage), from terrestrial, terrestrial-marine transitional, and marine settings around the margin of the Tethys, which include South China, North China, Junggar, Iran, and Oman cratons. Our research will focus on: 1) the sedimentary records of volcanism from the arc volcanisms in the Tethyan region based on mercury concentrations and its isotope records, temporal and spatial distributions of volcanic ash beds, as well as geochemistry of zircon; 2) the extinction and recovery models of primary producers both on land (e.g., plants) and in the ocean (e.g., algae and acritarchs) by integration of biological and geochemical proxies; 3) biological influences on environmental perturbations, such as the effects of land plants on atmospheric CO2 concentrations, continental weathering processes, and the effects of marine productivity on oceanic anoxia; and 4) the toxic effects to organisms (e.g., malformed evolution) of elevated heavy element fluxes (e.g., Hg, As, Pb, Ni) linked to volcanism and intense continental weathering. Our aim is to understand the cause-and-effect relationships among biological and environmental perturbations both on land and in the ocean during the Paleozoic-Mesozoic transition and their connection to evolution of the Tethys Ocean. This research would be a great example to explore the effects to the ecosystem perturbations in the earth surface by the evolutions of the Tethys.