THE ESTABLISHMENT OF THE HOLOCENE XUANREN AND TUOYANG FORMATIONS IN SHANXI

On the basis of previous work ,the Xuanren Formation consisting of river terrace Ⅰ deposits has been established with the section of ancient cultural remains at Xuanren Village ,Daixian,as the stratotype.This formation has a distinct binary structure and pronounced geomorphological features as well as isotope age data.It is in erosional unconformable contact with the underlying Zhiyu Formation.In light of geomorphological units and age data,the age range of the formation is 12000 2300 a ,assigned to early Holocene.The Tuoyang Formation has also been set up .It consists of the high floodplain terrace deposits and modern channel deposits ,belonging to the youngest fluvial deposits .It has prominent geomorphological features and is considered to be formed by redeposition after dissecting the Xuanren Formation （Ⅰ terrace deposits）.Its lower limit age is 2300 a ,pertaining to late Holocene.