摘要
地层不整合接触是研究地质发展历史及鉴定沉积盆地性质、地壳运动特征和运动阶段的重要依据。通过区域地质调查,结合不同时代地层沉积体系特征,在雪峰山西侧的石门—桑植复向斜早古生代末期—中生代地层中厘定出5个不整合面,由下而上分别是文洛克统小溪峪组与上覆中泥盆统云台观组、中二叠统梁山组或栖霞组之间的平行不整合面,上泥盆统黄家蹬组或写经寺组与中二叠统梁山组或栖霞组之间的平行不整合面,中三叠统巴东组与上三叠统九里岗组之间的平行不整合面,中三叠统巴东组与下—中侏罗统之间的角度不整合面,下白垩统石门组与下伏老地层之间的角度不整合面。这几个不同时代的不整合面代表了石门—桑植复向斜早古生代晚期—中生代地质演化时期中特定的构造事件。其中,小溪峪组与上覆泥盆系、二叠系系平行不整合关系反映雪峰古陆西侧隆后前陆盆地于文洛克世晚期受加里东运动影响隆升成陆并接受风化剥蚀;中泥盆统与中二叠统平行不整合是"柳江上升"和"黔桂上升"两次构造运动的产物;巴东组与九里岗组之间的平行不整合反映中三叠世晚期的早印支运动在研究区以水平抬升为主,横向挤压缩短较微弱;下—中侏罗统与巴东组角度不整合反映中三叠世晚期—早侏罗世晚印支运动NNW—SSE向强烈挤压使石门—桑植复向斜进一步收缩变窄,且形成一系列次级背向斜构造和挤压凹陷盆地;下—中白垩统呈串珠状角度不整合在下伏地层之上,主要反映早燕山构造运动。这些不整合面的厘定及其代表的相应构造事件为湘西北地区构造演化研究提供了更为详尽的地质信息,同时,对合理分析雪峰山西侧地区早古生代晚期—中生代沉积盆地属性提供了更仔细、更可靠的参考数据。
Stratigraphic unconformities provide important information about basin evolution and tectonic history. Based on 1：50 000 regional geological survey, five stratigraphic unconformities have been identi- fied in late Early Paleozoic- Mesozoic strata of the Shimen-Sangzhi synclinorium to west of the Xuefeng Mountain. In stratigraphic order, these unconformities are, （1） a parallel unconformity between the Wen- lock （Silurian） Xiaoxiyu Formation and the overlying Middle Devonian Yuntaiguan Formation and Middle Permian Liangshan Formation or Qixia Formation; （2） a parallel unconformity between Upper Devonian Huangjiadeng Formation or Xiejingsi Formation and Middle Permian Liangshan Formation or Qixia Forma- tion; （3） a parallel unconformity between Middle Triassic Badong Formation and Upper Triassic Jiuligang Formation; （4） an angular unconformity between Lower-Middle Jurassic strata and Middle Triassic Ba- dong Formation; and （5） an angular unconformity between Lower Cretaceous Shimen Formation and un- derlying strata. These unconformities represent separate tectonic events during the late Early Paleozoic to the Mesozoic. The first unconformity reveals that the foreland basin on the west side of the Xuefeng old land had uplifted under the influence of the Caledonian movement during the late Wenlock of the Silurian Period. The second disconformity is the result of two tectonic movements： the Liujiang uplift and the Qian ＂gui uplift. The third disconformity indicates that the early Indosinian movement mainly was uplift, with weak lateral extrusion and shortening. The fourth unconformity reflects that the strong NNW-SSE com- pression had further shortened the Shimen-Sangzhi synclinorium and formed a series of secondary oblique structures and basins influenced by the late Indosinian movement during the late Middle Triassic to Early Jurassic. The fifth unconformity mainly reflects the early Yanshan movement that closed the Jurassic ba- sins. These five unconformities and their corresponding te
出处
《地层学杂志》
CSCD
北大核心
2018年第1期75-89,共15页
Journal of Stratigraphy
基金
中国地质调查局地质矿产调查评价专项(12120113062100
2012011220510
2012011220511)资助
关键词
岩石地层
不整合面
沉积体系
构造运动
盆地属性
早古生代
中生代
石门-桑植复向斜
湖南
lithostratigraphy, unconformity, sedimentary system, tectonic movement, sedimentary basin, Paleozoic, Mesozoic,Shimen-Sangzhi synclinorium, Hunan
