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徐宿地区震旦纪地质事件及其成因讨论

潘国强, 刘家润, 孔庆友, 吴俊奇, 张庆龙, 曾家湖, 刘道忠   

  1. 南京大学 地球科学系,江苏 南京 210093
  • 收稿日期:2000-12-20 修回日期:2000-12-20 出版日期:2000-12-20 发布日期:2000-12-20

Study on Sinian Geologic Events in Xuzhou-Suzhou Area and Discussion on Their Origin

PAN Guo-qiang, LIU Jia-run, KONG Qing-you, WU Qun-qi, ZHANG Qing-long, ZENG Jia-hu, LIU Dao-zhong   

  1. Department of Earth Sciences, Nanjing University, Nanjing 210093, China
  • Received:2000-12-20 Revised:2000-12-20 Online:2000-12-20 Published:2000-12-20

摘要: 徐宿地区震旦系为陆表浅海沉积,沉积 相以碳酸盐台地相为主。在潮上-潮下低 能沉积中,常间有阵发性高能沉积,并伴生有异常沉积构造。这些异常沉积构造及同生阶梯 状小断裂多为古地震遗迹,据此可识别出五个古地震遗迹密集分布层段。在研究区至少有两 次浅成-超浅成基性岩浆侵入活动,分别发生在早震旦世和晚震旦世。地震事件、岩浆侵入 事件与海平面升降有成因联系。研究表明,研究区震旦纪地质事件受控于伸展构造,地质事 件发生于738.6~604Ma之间。这一时限与中-新元古代超大陆Rodinia在780~600Ma逐步裂 解的时间是一致的,因而徐宿地区震旦纪地质事件的起因可能与Rodinia的裂解过程有关。 由“古郯庐裂陷带”至北秦岭北部边界断层北侧可能就是当时华北板块边缘的板内裂解带。

Abstract: The Sinian strata in Xuzhou-Suzhou area are deposits of the epicontinental sea. They are mainly referred to the carbonate platform facies. In the supratidal to subtidal low-energy sedimental environments, sudden, violent high -energy sedimentation occasionally occur, which are often associated with some abn ormal sedimentary structures. These structures along with step-like small faul ts may indicate the ancient seismic traces. In the studied area, the Sini an seismic traces mainly include densely-spaced veins of micritic calcites, strongly scouring and erosion structures of "bag gutter" like, plastic rudites, eart hquake breccias, inter-formation folds and step-like small faults. Five disti ng uished stratomeres with closely-spaced seismic traces represen- ting five ear thqua kes phases have been recognized, which might include dozens, even hundreds of st rong earthquakes. At least two phases of hypabyssal to subsurface basic magmatic intrusions can be distinguished, occurring respectively in the early and late Sinian period. The seismic events, magmatic intrusions and sea-level changes a r e related in origin. Frequent, strong earthquake activities caused the sea-lev e l rise. The magmatic intrusions occurred in the interval between tow seismic ph ases and in the sea-level fall times.   The research results showed that the Sinian geologic events in the studied area might be controlled by extensional structures. The ages of these events ar e 738.6-604Ma, corresponding to the breakup times (780-600Ma) of global superc ontinent Rodinia. Therefore it is deduced that the origin of the Sinian geologi c events in Xuzhou-Suzhou area might relate to the breakup processes of Rodinia . The area from "Plaeo-Tanlu zone" to the north of boundary fault zone in the northern side of North Qinling Mountains might be the breakup zone within the North China Plate margin.