旋回地层学和天文时间带

CYCLOSTRATIGRAPHY AND ASTROCHRONOZONES

全球层型剖面和点(Global Stratotype Section and Point,GSSP)定义了地质时期大部分年代地层阶的底界,但无法对地层阶内部单元(单位层型)进一步划分和对比。本文对旋回地层学原理及其应用进行简要介绍,认为高分辨率旋回地层学和天文年代学识别出时间周期稳定的米兰科维奇旋回可为完整的沉积序列提供高分辨率的年代学约束,进而提出天文时间带的概念,即:将地层中受天文轨道作用力控制的沉积旋回校准至周期稳定的天文目标曲线(如偏心率、斜率、岁差)后形成的具有年代学意义、有全球对比潜力的地层时间单元。本文对天文时间带在新生代应用的经典范例进行介绍并探讨将其引入中生代和古生代的可能性。天文时间带是全球年代地层标准的有益补充,可使标准的地质年代、高分辨率综合地层及天文年代相结合。天文时间带在地质时间上既不受地层阶跨度的影响,又可为其单位层型的建立提供重要依据。

Global Stratotype Section and Point(GSSP)can define and correlate the stage boundaries,but not the body of the stage.In this paper,the principle and application of cyclostratigraphy has been introduced for solving this difficulty using high-resolution cyclostratigraphy and astrochronology.Recognizing of the stable Milankovitch cycle can provide unprecedented age control and ensure continuity of sedimentary successions.A concept of astrochronozones is proposed as’astronomical calibration of the sedimentary cycles into stable Milankovitch cycles(e.g.,eccentricity,obliquity,precession cycle)produces a potentially global correlated chronostratigraphic unit’.In this paper,the application of astrochronozones in the Cenozoic and further application in the Mesozoic and Paleozoic eras had been introduced.Astrochronozones,independent of the standard hierarchy in global chronostratigraphy,can combine the geochronology,integrated stratigraphy and astronomical time scale.The proposed astrochronozones contribute to the establishment of unit-Stratotype,preferably but not necessarily contains the stage.