国际第四纪年代地层研究进展

RECENT ADVANCES IN QUATERNARY CHRONOSTRATIGRAPHY

第四纪代表了地质历史时期最新的地质年代,持续了2.58个百万年,以两极发育冰盖、多期次的冰期-间冰期旋回和人属的出现为特征。第四纪年代地层学研究在建立高精度地层格架、了解地球气候系统演化规律和预测气候变化趋势等方面具有重要意义。依据现今的定义,第四系包括更新统和全新统,而更新统进一步划分为4个阶。其中,杰拉阶底界、卡拉布里雅阶底界和全新统底界全球层型剖面与点位(GSSP)已确立,而更新统中阶和上阶底界GSSP的研究工作正在进行中,界线标志已确定。近年来,随着同位素测年技术的不断提高和天文旋回理论的普遍应用,第四纪年代地层界线年龄在不断更新,天文轨道旋回控制的万年尺度气候事件可以作为全球对比的标尺。当前国际地层委员会第四系分会的主要任务包括更新统中、上阶底界金钉子的确立、全新统进一步划分和"人类统"概念的提出。

The Quaternary Period （2.58 Ma-present） is the most recent geological period, characterized by bipolar ice sheets, repeated transition between glacial and interglaical conditions and the first appearance of the genus Homo. Studies on the Quaternary chronostratigraphy play an important role in establishing high-resolution stratigraphic framework, understanding evolution pattern of Earth climate system, and predict-ing the climate trends in the near future. Based on the current definition, the Quaternary System is composed of Pleistocene and Holocene series, and the former can be further subdivided into four stages, including the Ge- lasian, Calabrian, middle and upper stages in ascending order. So far the Global Stratotype Section and Points （GSSPs） for the base of the Gelian and Calabrian stages and the Holocene Series have been formally defined, while all other official subdivisions are pending. With the improvement of radioactive isotope dating techniques and universal application of astronomical cycle theory, the ages of Quaternary chronostratigraphic boundaries have been improved and Milankovitch cyclicity in sediments can provide a precise and highly accurate Qua- ternary time scale for global correlation. At present, the main tasks for the Subcommission on Quaternary Stratigraphy include defining the middle and upper Pleistocene, subdividing the Holocene, and evaluating the ＂Anthropocene＂ concept.