晋东北地区侏罗纪地层划分、时代重新厘定及其地质意义

利用地层序列中火山碎屑岩、凝灰岩及其火山岩锆石U-Pb同位素测年,对晋东北地区侏罗纪地层时代进行了重新厘定。取得了以下主要认识:(1)确认宁武—静乐盆地下侏罗统永定庄组的存在;(2)宁武—静乐盆地天池河组可以与鄂尔多斯盆地安定组相对比,归属于中侏罗统;(3)浑源盆地髫髻山组应归属于中侏罗统上部,该套火山岩地层在整个燕—辽地区具有穿时性;(4)广灵盆地中侏罗统窑坡组底部厚层砾岩的沉积时代可能与燕山造山带的南大岭组相当,应该属于早侏罗世至中侏罗世早期构造运动的产物。通过地层序列的重新厘定,确认了159.0~(152.77±0.63)Ma区域角度不整合的存在,该期构造运动可能与侏罗纪东亚大陆多向汇聚产生的远程效应有关。

Redefinition of Jurassic strata in northeastern Shanxi and its tectonic implications

Abstract: Based on regional stratigraphic correlation and using zircon dating method of tuff and volcaniclastic rocks in the Jurassic stratigraphic sequence, the authors re-divided and defined Jurassic stratigraphic sequence. Some conclusions have been reached: (1) The stratigraphic age of Yongdingzhuang Formation in Ningwu-Jingle basin is identified as the lower Jurassic; (2) The middle Jurassic Tianchihe Formation may be compared to Anding Formation of Ordos basin, and therefore the stratigraphic age of Anding Formation in the controversy should be redefined to the middle Jurassic; (3) The Tiaojishan Formation is redefined to the middle Jurassic in Huyuan basin, this stratum has the diachronistic nature in the Yanshan orogenic belt; (4) The sedimentary time of basal conglomerate of Yaopo Formation in Guangling basin can be equivalent to Nandaling Formation of Yanshan orogenic belt, the basal conglomerate should be the product of tectonic movement in early Jurassic and early middle Jurassic. By the redefinition and redivision of Jurassic stratigraphic sequence in northeastern Shanxi, the angle disconformity between 159.0Ma and (152.77±0.63) Ma is confirmed, and this is dynamically associated with distant field effects produced by synchronous convergences toward the East Asia continent of different plates (Siberia, Paleo-Pacific, Tethys).