白垩纪晚期-古近纪早期热事件研究进展

由于化石燃料大量燃烧，大气CO₂浓度跟温度都呈现快速上升趋势，这两者之间的关系是学术界研究的热点。地质历史时期发生过多次的快速增温事件，伴随着大气CO₂浓度的增加，通过研究这些气候相似型可以为上述问题提供参考和借鉴。白垩纪晚期-古近纪早期（约67~52 Ma）是地质历史时期中典型的温室气候期，在这一时期发生了一系列快速和短暂的增温事件（热事件）。热事件的发生伴随着碳同位素负偏移（CIE）、碳酸盐补偿深度（CCD）变浅、大气中CO₂含量增加及温度升高等现象，一些热事件同时还出现了环境变化和生态效应。这给我们提供了机会来研究气候变化和碳循环之间的耦合规律，帮助我们更好地预测未来气候、环境和生物变化。文章根据最新的研究成果，对白垩纪晚期-古近纪早期的热事件识别、触发机制及碳来源作了综述并提出展望。目前全球近200个地点发现系列热事件记录，绝大部分记录来自海相沉积，陆相沉积记录很少；热事件的触发机制主要有天文轨道周期、火山活动、地外天体撞击、构造抬升作用等观点；热事件碳来源主要有泥炭、永久冻土、甲烷水合物、火山及地外天体。在今后的热事件研究中应加强：1）陆相记录及其与海相记录的对比研究；2）不同热事件触发机制研究，尤其是古新世-始新世极热事件（PETM）、马斯特里赫特期末期增温事件（LMWE）等这些能够造成严重环境变化和生态效应的热事件；3）碳来源方面的研究，进一步了解几大碳库碳释放的通量和特征，并且结合地质记录、模型模拟及示踪元素来揭示热事件的碳来源。

A REVIEW ON THE HYPERTHERMALS FROM LATE CRETACEOUS TO EARLY PALEOGENE

Due to the burning of massive fossil fuels, atmospheric CO2 concentration and temperature are increasing rapidly. The coupling correlation between the atmospheric CO2 and temperature is a hot topic. Many rapid warming events occurred in geological history, accompanied by the increase of atmospheric CO2 concentration, which could be regarded as reference for the global warming at present. The Late Cretaceous to Early Paleogene(ca. 67~52 Ma) is a typical greenhouse climate period, during which a series of rapid and transient warming events(termed "hyperthermals") occurred. These hyperthermals were characterized by significantly negative carbon isotope excursion(CIE), associated with shoaling of the carbonate compensation depth(CCD), and increasing atmospheric CO2 and temperature. Some hyperthermals also caused environmental changes and ecological effects. Studying these hyperthermals are benefit for understanding the coupling correlation between climate change and the carbon cycle, so that can help us to predict the climate, environmental and biological changes in the future. In this study, we reviewed the characteristics, triggering mechanisms and carbon sources of hyperthermals in the Late Cretaceous to Early Paleogene. So far, hyperthermals have been found at nearly 200 locations around the world, most of which are from marine sedimentary records. The forcing mechanisms of hyperthermals mainly includes astronomical orbital, volcanic activities, extraterrestrial impacts and/or tectonic uplift. The main sources of the light carbon could be peatlands, permafrost, methane hydrate, volcanism and/or extraterrestrial comets. In the future, more works should be focused on: (1) Providing more terrestrial records and comparing them with marine records; (2) Revealing the forcing mechanisms for different hyperthermals, especially the Paleocene Eocene Thermal Maximum(PETM) and Late Maastrichtian warming event(LMWE), which can cause serious environmental changes and ecological effects; (3) Understanding the flux and characteristics of potential carbon sources, moreover, there is a need to combine geological records, model simulation and tracer elements to reveal the exact carbon sources of hyperthermals.