鄂西中央背斜带中生代构造演化过程:来自磷灰石裂变径迹的证据

The Tectonic Evolution of the Central Anticline in Western Hubei of China during Mesozoic:Evidences from Apatite Fission Track

鄂西中央背斜带位于扬子陆块扬子碳酸盐台地构造区和川中(鄂西)前陆盆地构造区,构造形迹保存完整,对于研究区域构造演化具有重要的区域优势.根据详细的野外地质调查,结合磷灰石裂变径迹模拟将本区侏罗纪以来的构造活动分为5个主要期次:(1)187.4~180.1Ma之间的早侏罗世时期,本区地层发生隆升,导致了九里岗组与桐竹园组之间的平行不整合;(2)180.1~115.6Ma的侏罗纪中晚期至早白垩世,发生区域沉降,并接受陆相碎屑沉积;(3)115.6~78.8Ma的白垩纪晚期,再次缓慢隆升并遭受剥蚀;(4)78.8~63.6Ma的白垩纪末至古近纪初,再次发生构造沉降,沉积了白垩系跑马岗组;(5)之后,本区总体处于大幅度构造隆升状态,但2.6Ma后的第四纪开始有小幅沉降.根据以上构造演化历史,结合平衡剖面技术定量重建了本区区域挤压-伸展过程.

The central anticline of the western Hubei is located in the tectonic zone of the Yangtze block and the central Sichuan（western Hubei）foreland basin,which possesses important advantages for the study of regional tectonic evolution.In this paper,according to the detailed field geological survey and evidences form apatite fission track simulation,five stages of tectonic activities have been identified：（1）tectonic uplift at 187.4 Ma-180.1 Ma that resulted in the parallel unconformity between the Jiuligang Formation and the Tongzhuyuan Formation.（2）tectonic subsidence and deposition of terrestrial sediments at180.1 Ma-115.6 Ma.（3）slowl tectonic uplift once again associated with land erosion during 115.6 Ma-78.8 Ma.（4）subsidence again and the deposition of Cretaceous Paomagang Formation during the period of 78.8 Ma-63.6 Ma.（5）followed by great uplift until a small subsidence at 2.6 Ma of the Quaternary.Based on the tectonic evolution and the application of balanced profile technology,the regional tectonic pattern of extrusion-stretching process was established.