Abstract: During the Late Jurassic to Late Cretaceous,the northern Yangtze area has evolved into a late-orogenic tectonic regime,which is characterized by the development of several thin-skinned foreland fold-thrust belts,including Dabashan,Dahongshan and eastern Sichuan-western Hunan and Hubei fold-thrust belts.They all show arc-shape geometries and generally trend parallel to the Qinling-Dabieshan Orogen and Xuefengshan Orogen.Synthesis of structural mapping,sedimentary facies and provenance analyses revealed that these arcuate fold-thrust belts not only deformed the original foreland sequence,but also controlled the basin evolution during the Late Jurassic through Late Cretaceous.Here we define the late-orogenic tectonic-paleogeography evolution into three phases as (1)From Late Jurassic to early Early Cretaceous: The Dahongshan and Dabashan fold-thrust belts initially propagated southwestwards and controlled the deposition of Penglaizhen Formation in northern Sichuan Basin and Zigui Basin.The original foreland basin was bounded by eastern Sichuan-western Hunan and Hubei fold-thrust belt to the southeast and Longmenshan fold-thrust belt to the west,leading to an intracratonic basin with foredeep subsidence which is also referred as “walled sedimentary basin”.(2)From middle Early Cretaceous to late Early Cretaceous: The propagation of the Dahongshan and Dabashan fold-thrust belts attenuated,while the eastern Sichuan-western Hunan and Hube fold-thrust belt continued the northwestward propagation and formed the structural lines trending northeast.On the front of the eastern Sichuan-western Hunan and Hubei fold-thrust belt,the depocenter of the basin was located near Yichang city where the Huangling anticline has yet been exposed.(3)During the Late Cretaceous: The eastern Sichuan-western Hunan and Hubei fold-thrust belt propagated northwestly with slight change of the structural trends from northeast to north-northeast.The Huangling anticline was initially formed during this period.The depocenter of the basin located on the two ends of the eastern Sichuan-western Hunan and Hubei fold-thrust belts with Yichang on the north end and Xishui on the south end.Meanwhile,there are also many wedge-top sediments developed inside the fold-thrust belt,leading to the formation of several piggy-back basins such as Enshi basin,Qianjiang basin and Laifeng basin.

Key words: arcuate fold-thrust belt, foreland basin, northern Yangtze area, piggy-back basin

摘要： 扬子北缘晚造山阶段(即晚侏罗世—晚白垩世)发育以弧形构造为特征的前陆薄皮逆冲—褶皱构造,包括了沿秦岭—大别造山带发育的北西向的大洪山和大巴山弧形带,以及沿江南—雪峰造山带发育的北东向的川东—湘鄂西弧形带。详细的构造解析、盆地沉积及物源特征综合分析表明,弧形构造不仅将早期的前陆序列卷入变形,并且控制了晚侏罗世—晚白垩世的盆地演化和古地理格局。总结扬子北缘晚造山阶段的盆山演化特征,可以将其划分为3个阶段:(1)晚侏罗世—早白垩世早期,大洪山和大巴山弧形带的发育控制了四川盆地东北部及秭归盆地上侏罗统蓬莱镇组的沉积,川东—湘鄂西弧形带限制了盆地的东南边界,加之位于四川盆地西部的龙门山逆冲带,三面围限构成具前渊沉降的克拉通内盆地或称为“墙围盆地”(walled sedimentary basin);(2)早白垩世中期—早白垩世晚期,大洪山和大巴山弧形带的逆冲构造变形逐渐减弱,而川东—湘鄂西弧形带继续向北西扩展,构造线呈北东向展布,在弧形带前缘的宜昌地区形成沉积中心,并覆盖了现今的黄陵背斜;(3)晚白垩世,川东—湘鄂西弧形带继续向北西推进,构造线呈北北东向展布,弧形带北翼的黄陵背斜初始隆起,沉积中心分别位于北翼宜昌地区及南翼习水地区。与此同时,在弧形带内部薄皮构造的向斜部位形成楔顶沉积,发育如恩施盆地、黔江盆地、来凤盆地等一系列规模较小的背驼式盆地。

关键词: 弧形构造, 前陆盆地, 扬子北缘, 背驼式盆地

CLC Number: 

• P547