CAJ | 학술논문

华南地区新元古代地层区域上涉及中国上、下扬子地区,包括中国地层表中的青白口系、南华系和震旦系,时代上分别对应国际地层年代表中拉伸系、成冰系和埃迪卡拉系。传统划分是以晋宁运动(四堡运动)为标志划分为中元古界和新元古界,近年来,通过地层中凝灰岩锆石SHRIMP U-Pb的测定,华南地区新元古代年代表已进行了有效年代学标定,突出了地层对比的可靠性和新的构造观点解译。华南古陆构造演化研究需要以构造为纲,明确了古陆周缘地层发育了中元古代晚期相关沉积记录,而华南古陆内部,特别是江南造山带为武陵运动的构造运动产物。本文将报道桂西地区青白口系拱洞组底部SHRIMP锆石U-Pb年代学测定数据(799.8±5.5) Ma,江西与湖南交界长安组底部获得凝灰岩锆石年龄(770±10) Ma,湘西北长安组底部获得凝灰岩锆石年龄(758.6±5.4) Ma和湾溪口村长安组冰碛岩距底部十多米处获得凝灰岩锆石年龄(743.8±4.1) Ma。上述年龄进一步提供华南地区冰碛岩地层的年代学依据。
화남지구신원고대지층구역상섭급중국상、하양자지구,포괄중국지층표중적청백구계、남화계화진단계,시대상분별대응국제지층년대표중랍신계、성빙계화애적잡랍계。전통화분시이진저운동(사보운동)위표지화분위중원고계화신원고계,근년래,통과지층중응회암고석SHRIMP U-Pb적측정,화남지구신원고대년대표이진행료유효년대학표정,돌출료지층대비적가고성화신적구조관점해역。화남고륙구조연화연구수요이구조위강,명학료고륙주연지층발육료중원고대만기상관침적기록,이화남고륙내부,특별시강남조산대위무릉운동적구조운동산물。본문장보도계서지구청백구계공동조저부SHRIMP고석U-Pb년대학측정수거(799.8±5.5) Ma,강서여호남교계장안조저부획득응회암고석년령(770±10) Ma,상서북장안조저부획득응회암고석년령(758.6±5.4) Ma화만계구촌장안조빙적암거저부십다미처획득응회암고석년령(743.8±4.1) Ma。상술년령진일보제공화남지구빙적암지층적년대학의거。
Neoproterozoic strata in South China consist of Qingbaikouan, Nanhuan and Sinian systems in Chinese Time Scale which can be respectively correlated with Tonian, Cryogenian and Ediacaran systems in the International Time Scale. The South China area is subdivided into two parts, i.e., Upper and Lower Yangtze blocks. Traditionally, the Jinning Movement or Sibao Movement is regarded as the marker for the boundary between the Mesoproterozoic and the Neoproterozoic. In recent years, the SHRIMP U-Pb determination of the tuff zircons from the strata has yielded effective dating data for chronology of Neoproterozoic strata, which give prominence to the reliability of the stratigraphic correlation and add interpretation of new tectonic viewpoints. We should take the tectonic as the key to tectonic evolution studies so as to reconfirm the depositional records of Late Mesoproterozoic on the margin of South China. However, the Sibao movement is a late orogeny in the interior of South China old land. The new chronostratigraphic data promote tectonic division, stratigraphic correlation and understanding of stratabound deposits. At the same time, a framework will contribute to the stratigraphic correlation of global and continental blocks. In this paper, the authors present the SHRIMP zircon U-Pb data ((799.8±5.5) Ma) obtained at the bottom of Qingbaikouan Gongdong Formation in western Guangxi, the SHRIMP zircon U-Pb age of (770±10) Ma for the Chang’an Formation in Jiangxi- Hunan border area, the SHRIMP zircon U-Pb age of (758.6±5.4) Ma for the bottom of the Chang’an Formation in western Hunan, and the SHRIMP zircon U-Pb age of (743.8±4.1) Ma for the strata 10 m above the bottom of the Chang’an Formation at Wanxikou Village. These data further provide the geochronologic basis for dismictite strata in South China.