华北克拉通晚三叠世沉积盆地原型与破坏早期构造变形格局

华北克拉通破坏的过程在地壳浅层沉积和构造变形中留有相应的建造和改造形迹。本文在前人研究基础上，据钻井、地震剖面和露头资料揭示的地层分布、沉积面貌以及构造变形特征，综合论述了印支期华北克拉通的沉积盆地原型及与克拉通破坏早期构造变形之间的响应关系。晚三叠世，华北克拉通残留地层具有分区分布特点： 克拉通腹地的鄂尔多斯地区上三叠统延长组发育较全，向东延展至晋中、豫西一带； 克拉通北缘的上三叠统杏石口组（及同期老虎沟组、黑山窑组等）沿辽西—京西—冀北一线零星分布； 克拉通南缘上三叠统沿豫南—陕南一线发育在北秦岭一带。南、北两缘晚三叠世地层均已卷入同期和后期构造变形，多被逆冲断层夹持并呈断片状产出。从构造变形角度，晚三叠世华北克拉通两侧均已发现大规模的南北向挤压构造，大致形成“对冲”格局，与内克拉通先存的东西向构造线一致。同生沉积记录了区域构造变形过程和/或由变形等因素控制的抬升剥蚀信息。在内克拉通，西部鄂尔多斯地区构造稳定，变形轻微，残留地层较全；东部地区抬升强烈，上三叠统大多数缺失；在东、西部之间存在一个沉积—构造的“缓冲”过渡区。从盆地原型恢复角度，晚三叠世华北克拉通表现为南北两缘陆内前陆盆地镶边的内克拉通盆地格局。华北克拉通腹地的盆地原型是叠覆在早—中三叠世盆地之上的继承性内克拉通盆地。华北克拉通北缘的陆内前陆盆地系统由阴山—燕山楔顶带、张家口—承德前渊带、清水河—山海关前隆带和京西—柳江隆后坳陷带构成；南缘的陆内前陆盆地系统则为北秦岭楔顶带、平凉—南召前渊带、环县—霍邱前隆带和铜川—济源隆后坳陷带。其中的铜川—济源和京西—柳江两个隆后坳陷带则可归属于华北内克拉通盆地。

Prototypes of Late Triassic Sedimentary Basins of North China Craton (NCC) and Deformation Pattern of Its Early Destruction

The corresponding construction and transformation features remain in the shallow crust deposition and tectonic deformation during the destruction progress of North China Craton (NCC). On the basis of previous researches and the features of stratigraphic distribution, sedimentary and tectonic deformation, which are revealed by well drill, seismic profile and outcrop data. This paper discusses the response relationship between sedimentary basin prototype of the NCC and the early tectonic deformation of Craton destruction. During Late Triassic, the residual formation was in the characteristic of banded distribution: (1) the Upper Triassic Yanchang Formation develops well in the Ordos basin, the center of the NCC, and it extended eastward to central Shanxi and western Henan area; (2) the Upper Triassic Xingshikou Formation (and the contemporaneous Laohugou Formation and Heishanyao Formations) on the northern margin of the craton distributed sporadically along the line of western Liaoning—western Beijing—northern Hebei; (3) on southern margin of the craton, the Upper Triassic developed in the northern Qinling area, along the line of southern Henan—Southern Shaanxi. Both the Upper Triassic in the northern and southern margins of the craton had been involved into contemporaneous and deuteric tectonic deformation, most of the formations had been clamped by thrust faults and produced in the shape of fragment. From the perspective of tectonic deformation, Late Triassic large-scale S—N trending compressional structures had been discovered on both margins of the NCC, and they had formed "Hedge patterns", which was in consistent with the existed E—W structure lines in intracraton. Syngenetic deposition recorded the process of regional tectonic deformation and/or the information of uplift and denudation controlled by deformation or other causes. In the intracraton, the western Ordos area was stable in tectonics, had weak deformation, and more complete residual strata; the eastern area uplifted intensely, most of the Upper Triassic strata is absent; and the central part, between eastern and western area, is a sedimentary—tectonic "buffering" transition region. From the perspective of prototype basin reconstruction, the NCC in Late Triassic is an intracontinental basin with foreland basins on both northern and southern margins. The prototype of the central NCC is an inheritance intracraton basin which overlays on the Lower—Middle Triassic basin. The intracontinental foreland system on the northern margin of the NCC consists of the Yinshan—Yanshan wedge-top belt, Zhangjiakou—Chengde foredeep, Qingshuihe—Shanhaiguan fore-bulge and western Beijing—Liujiang back-bulge depozones; and the intracontinental foreland system on the southern margin consists of the northern Qinling wedge-top belt, Pingliang—Nanzhao foredeep, Huanxian—Huoqiu fore-bulge and Tongchuan—Jiyuan back-bulge depozones. Of them, the Tongchuan—Jiyuan and western Beijing—Liujiang back-bulge depozones can also be allocated into the intracraton basins.