西秦岭及其邻区中—新生代红层地层包括白垩系、古近系和新近系.这些红层地层的沉积组合、构造变形、空间分布及相互关系等是西秦岭中—新生代陆内地质过程的客观记录,对其系统研究是重建西秦岭及其邻区中—新生代构造演化过程之基础.依据这些红层地层之间的角度不整合、沉积序列与沉积环境、空间分布型式和构造线方向及构造样式,西秦岭及邻区中—新生代红层地层可分为早白垩世、晚白垩世、古近纪—新近纪三个构造层.三个构造层对应于西秦岭中—新生代陆内构造演化的三个不同阶段,即早白垩世北东向盆—山构造、晚白垩世区域左旋走滑拉分构造和渐新世—上新世区域伸展泛盆地阶段.结合印支期多块体拼贴形成的中国大陆中—新生代陆内构造格局与岩石圈动力学过程分析,认为西秦岭早白垩世北东向盆山构造格局是中生代以来西太平洋板块向西俯冲导致的东亚区域性伸展构造的组成部分;晚白垩世走滑拉分盆地则是白垩纪拉萨地块与羌塘—昌都地块汇聚碰撞背景下中国西北大陆区域性左旋走滑作用的结果;而渐新世—上新世的泛盆地阶段则指示了印度板块与欧亚板块碰撞的远程构造—地貌响应之前经历了漫长区域伸展均衡坳陷和侵蚀夷平期,这说明上新世,西秦岭尚未成为现今青藏高原的组成部分,也就是说新生代以来印度板块与欧亚板块碰撞汇聚的构造响应起始于上新世末期.
The Mesozoic—Cenozoic red bed strata in the Western Qinling Mountains and its adjacent area include the Cretaceous,Paleogene,Neogene.These different age red bed strata have different characteristics in sedimentary sequences,tectonic deformation,spatial distribution and geological relations,which are the objective records of the Mesozoic—Cenozoic intracontinental tectonic process of the Western Qinling Mountains.Therefore,regionally systematical study for those different age red bed strata is foundation for understanding Mesozoic—— Cenozoic tectonic evolution of the Western Qinling Mountains and its adjacent areas.Based upon the unconformities between different red bed strata and underlying strata,distinct characteristics of those different red bed strata in sedimentary sequence,tectonic line and structural form,spatial distribution,Mesozoic—Cenozoic red bed strata in Western Qinling Mountains and its adjacent areas can be divided into three tectonic layers,that is,the early Cretaceous,late Cretaceous and Paleogene—Neogene.Although the nowadays spatially distribution of the three tectonic layers has been separated and dissected by the latest plateau uplift and erosion,the three different tectonic evolution stages of Mesozoic—Cenozoic tectonic evolutionin the Western Qinling Mountains and adjacent regions can still be determined.Three tectonic layers correspond to Early Cretaceous extensional rifting basin development stage,Late Cretaceous strike-slipping pull-apart depression stage and Oligocene—Pliocene regional depression basin development stage.In consideration of tectonic framework and lithosphere Dynamics process of Chinese continent after Indosinian collision-orogeny,it is suggested that Early Cretaceous Northeast extensional rifting basin should be the part of Eastern Asian regional extension tectonic system formed by the westward subduction of Western Pacific plate to Eurasian plate since Mesozoic,Late Cretaceous strike-slipping pull-apart depression basin may be the result of left strike-s