摘要
本文重新厘定了扬子地块西北缘晚古生代至早中生代沉积盆地的原型,在综合分析南秦岭造山带和勉略缝合带形成规律的基础上,对于南秦岭造山带与扬子地块北缘的拼合演化历史以及盆山耦合关系进行了研究。指出在晚二叠世晚期(长兴组沉积上段)和早三叠世早期(飞仙关组沉积下段)发生点式碰撞,在两个不同的大地构造单元之间形成了与碰撞相关的裂谷盆地群(包括开江-梁平裂谷、城口-鄂西裂谷和东部的当阳裂谷等),碰撞裂谷群的持续演化时间为5～6Ma,这一阶段典型的沉积标志为水下早期阶段形成的海相磨拉石层序。至早三叠世的嘉陵江二段沉积时期,两个不同地块的持续拼合导致大巴山和米苍山地区与周缘前陆盆地相关的古冲断带的形成,该阶段在缝合带接触部位发育角度不整合和河流相沉积,扬子地块其余大部仍然是保持连续的海相碳酸盐岩沉积。晚三叠世南秦岭造山带与扬子北缘之间的残余大洋消失,为整体闭合的碰撞后期阶段,沉积了须家河组开始的陆相碎屑岩系,大巴山和米苍山地区进入到了以陆相磨拉石为主的前陆盆地阶段,在扬子北缘形成了神农架-黄陵隆起和米苍山隆起。晚三叠世以后大巴山和米苍山地区进入了比较复杂的后期改造阶段,产生了多期的收缩性构造活动,包括以形成区域性的假整合和小角度不整合为特征的晚侏罗世-早白垩世早期(J_3-K_1)的低幅度活动期;以大巴山和米苍山冲断带的强烈改造为主,形成薄皮冲断构造系统的早白垩世晚期变形和以形成大巴山弧形冲断带和米苍山基底卷入的冲断带为特征的新生代晚期变形。
In this paper, we studied the prototype of the Late Paleozoic-Early Mesozoic sedimentary basins in the northwestern margin of the Yangtze block systematically. Together with the synthetical analysis on the formation of the South Qinling orogen and the Mianlue suture, we discuss the collision history and basin-range coupling between the Yangtze block and the South Qinling orogen. Our result indicates that the initial contact between the two tectonic units occurred as early as the late period of Late Permian （upper member of Changxing Formation） and the early period of Early Triassic （lower member of the Feixianguan Formation）. Several collision-related rift basins, including the Kaijiang-Liangping rift, the Chengkou-Exi rift and the Dangyang rift formed between the two tectonic units at that time from west to east. They lasted for ca. 5~6Ma and were characterized by the deposition of marine molasse sediments. During the period when the second member of the Jialingjiang Formation （Early Triassic） was deposited, the paleo-thrust belts related to the peripheral foreland basin formed near the Daba Shan and the Micang Shan due to the sustaining collision of the two blocks, which led to the formation of angular unconformity and the deposition of fluvial sediments near the suture. While far away from the suture, marine carbonate deposition remained dominating. During the Late Triassic, the South Qinling orogen and the Yangtze block collided completely and the ocean between them disappeared. Marine deposition ceased since then, and the foreland basin which was characterized by terrestrial molasse sediments started to develop in the front of the Daba Shan and the Micang Shan, the Shengnongjia-Huangling uplift and the Micang Shan uplift formed in the northern margin of the Yangtze block as well at the time. The Daba Shan and the Micang Shan areas were complicatedly altered by multi-stage contractional tectonic events since the Late Triassic, including the weak tectonic activity during the Late Jurassic and the early stage of the Early Cretaceous （J3-K1） marked by regional disconformities and low-angular unconformities, the late stage of the Early Cretaceous characterized by the thin-skinned thrusting, and the strong deformation during the Late Cenozoic that was dominated by arc thrusting in front of the Daba Shan and basement-involved thrusting in front of the Micang Shan.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2011年第3期601-611,共11页
Acta Petrologica Sinica
基金
"十五"国家重点科技项目(攻关)计划(2001BA605A06-01)
"十一五"国家重大专项(2008ZX05003-001)联合资助
关键词
秦岭造山带
扬子地块
米仓山
大巴山
碰撞裂谷
前陆盆地
盆山耦合
Qinling orogen
Yangtze block
Micang Shan
Daba Shan
Collision rift
Foreland basin
Basin-mountain coupling
