ON THE ZHONGTIAO MOVEMENT

In this paper the author discusses some problems on the Zhongtiao move- meat, and compares the Zhongtiao movement with the Luliang and Zhongyue movements with respect to time and space （see Table 3 and Fig. 6）. The Zhongtiao movement is without doubt the most important crustal movement in the tectonic development of the early Proterozoic in the North China platform （the Sino-Korean paraplatform）. It is due to its clear chronohorizon and the presence of distinct angular conformities that the Zhongtiao movement （or the Zhongtiao cycle） has been considered to be the representative of the crustal movements in the late part of the early Proterozoic. On the basis of new data obtained in mineral prospecting in the Zhongtiao Mountains area, three episodes may be distinguished in the Zhongtiao movement. The first episode, represented by unconformities between the Xiaozhongtiao and Xiaxian Subgroups of the Zhongtiao Group, led to partial inversion of the Zhongtiao geosyncline. The second episode （the main episode）, occurring between the Xiaxian and Danshanshi Subgroups, is an important folding episode, It marked the end of the geological history of the geosyncline, and brought about folding, fracturing, regional metamorphism and magmaticintrusion. The isotopic age （metamorphic age） is about 1800 m.y. The third episode （the last episode）, occurring between the Danshanshi Subgroup of the Zhongtiao Group and the Xiyanghe Group （sedimentary cover）, resulted in the formation of a unified Zongtiao geosynclinal fold belt.Therefore the Zhongtiao movement meets the requirements of a type section of the crustal movements.