湖北当阳陆相白垩系-古近系界线层型研究

The mass extinction of terrestrial dinosaurs is one of the most conspicuous events across the Cretaceous-Paleogene Boundary（KPB）. The Continental strata are important information carriers of the events.The continental strata of the Cretaceous and the Paleogene are well developed in the world. Significance of establishing a continental KPB stratotype is no less than establishing the GSSP. Since ongoing work to establish stages of continental strata and the Stratigraphic Chart of China is being conducted in China, it is more imperative to establish the continental KPB stratotype for China. The continuous biostratigraphic record of the Cretaceous-Paleogene transition is scarce in the continental domain, and establishing the continental KPB stratotype is very difficult.In the outcrop section at Dangyang, Hubei province (China), the KPB is situated in a set of grayish-brown silty mudstone beds deposited continuously, with a minimum interval of 35 cm between the fossiliferous latest Cretaceous and earliest Paleocene beds.The strata around the boundary is rich in charophytes and ostracods. And the Dangyang section is one containing the most continuous and abundant terrestrial biostratigraphic record of charophytes etc.from the Cretaceous-Paleogene transition known so far in the world; and it is the only one known so far in China that has a potential to become a continental stratotype of the KPB and a stratotype of the lowermost stage of the Paleocene, Paleogene and Cenozoic of China.Therefore, the Dangyang section is undoubtedly worth further investigation in greater detail. This project will develop a synthetical investigation, which takes biostratigraphy of charophytes, palynology etc. as a principal subject, and carry researches on the Dangyang stratotype section forward.

陆生恐龙的绝灭是白垩-古近系界线（KPB）事件中最引人注目的。陆相地层是恐龙绝灭等事件信息的重要载体，白垩、古近纪全球陆相地层发育，建立陆相KPB层型的意义实际上不亚于建立GSSP。目前我国正在开展陆相地层建阶和建立"中国地层表"工作，建立陆相KPB层型对于中国来说更具迫切性。由于全球连续的陆相的界线生物地层记录十分匮乏，建立陆相KPB层型非常困难。湖北当阳露头剖面KPB位于一连续沉积的粉砂质泥岩层内，含白垩纪最晚期和古新世最早期生物群的两样品间的最小层距为35cm，界线上、下轮藻、介形类都非常丰富，是全球迄今所知KPB时期轮藻等陆相生物地层记录最连续丰富的剖面，是中国迄今所知唯一可能成为陆相KPB层型及中国古新统、古近系和新界第一阶层型的 "潜在的双重层型剖面，无疑，当阳剖面值得进一步深入研究。本项目拟开展以轮藻、孢粉等生物地层学为主的综合研究，把有关当阳"双重层型"的研究工作推进一步。

陆生恐龙绝灭是白垩-古近系界线事件中最引人注目的。陆相地层是该事件信息的重要载体。白垩、古近纪陆相地层发育，建立陆相白垩-古近系界线层型很有必要，其意义不亚于建立GSSP。中国的白垩、古近系多为陆相沉积，界线方面存在许多问题，目前中国正在开展陆相地层建阶和建立中国地层表工作，建立陆相白垩-古近系界线层型对中国更具迫切性，因为陆相为主的中国新生界第一阶只能由它的下界的界线层型、也即陆相白垩系/古近系界线层型来定义。全球白垩-古近纪过渡时期连续的陆相生物地层记录十分匮乏，建立陆相白垩-古近系界线层型非常困难。李伟同在Li Wei-Tong,1998的法文专著中揭示湖北当阳跑马岗组露头剖面拥有白垩纪-古近纪过渡时期、特别是古新世早期全球至今所知的最连续丰富多样的轮藻生物地层记录。经包括本项为期一年的科学部主任基金项目在内的科学基金项目研究，湖北当阳露头剖面的白垩-古近系界线位于一连续沉积的灰褐色粉砂质泥岩层内；含白垩纪最晚期和古新世最早期生物群的两样品间的最小层距为35cm；界线上、下轮藻、介形类都非常丰富，1kg岩样最多可产轮藻化石约1万个；是中国迄今所知唯一的可能成为全球或区域性的陆相白垩-古近系界线层型及中国古新统、古近系和新界第一阶层型的剖面。2014年，题为《中国新生界第一阶潜在的层型剖面》和《A potential stratotype for the regional lowermost stage of the continental Paleocene in China》的文章在《中国科学: 地球科学》和《Science China: Earth Sciences》上分别刊出，集中反映了上述的基金研究的科学成果。本次结题的科学部主任基金项目取得的另一重要成果是新撰的题为《“冠女星介Cristocypridea”（Talicypridea）的模式产层为古新统》的文章已于2014年岁末投到《中国科学: 地球科学》杂志（目前已通过初审），为解决介形类与轮藻关于当阳剖面白垩系/古近系界线看法分歧、进而推进当阳陆相白垩-古近系界线层型和中国新界第一阶的建立迈出重要的一步。