摘要:渭河盆地、渭北隆起及东秦岭造山带地处青藏块体东北缘、华北克拉通和扬子克拉通的交界处，形成了特有的盆山体系，分布有油气、氦气及地热等多种能源矿产资源。新生代是渭河盆地沉积—构造演化及渭北隆起和东秦岭隆升的重要时期，缺乏该时期盆山体系耦合关系的研究，制约了对区域矿产资源分布规律的认识。盆山耦合体现在时间、空间、物质、构造作用及地表形态等多方面。以大量钻孔资料为依托，运用“回剥法”分析了渭河盆地新生代的沉降幅度及沉降速率，并根据主沉降期新近纪以来不同阶段沉积地层厚度展布特征恢复了盆地沉积演化历史。研究表明渭河盆地新生代以来沉降中心具有自西南方向西安凹陷向北东方向固市凹陷迁移的特征。古近纪始新世以来，渭河盆地发生快速构造沉降，中新世早-中期以西安凹陷为主要沉积、沉降中心，晚中新世以来以西安、固市两个凹陷为主要沉积、沉降中心，晚上新世—早更新世沉降中心转移到东北部固市凹陷，晚更新世以来，西安凹陷和固市凹陷均发生快速沉降。裂变径迹的分析测试结果表明渭北隆起约45～32 Ma整体快速抬升，同步于东秦岭太白山和华山约57～40 Ma的快速隆升阶段，与渭河盆地古近纪始新世约40 Ma的基底快速沉降具有耦合关系。晚中新世约7.3 Ma以来，渭河盆地的持续快速沉降，与渭北隆起上新世约5 Ma及东秦岭太白山约10～9.6 Ma、华山约8～5 Ma以来的快速耦合关系明显。太平洋板块的俯冲、欧亚板块与印度板块始新世约55～45 Ma碰撞及青藏高原约10～8 Ma隆升外扩的远程效应对研究区影响较大。
关键词: 等厚图/
裂变径迹/
沉积—构造演化/
隆升剥蚀/
盆山关系/
渭河盆地/
渭北隆起/
东秦岭造山带
Abstract:The Weihe Basin, Weibei uplift and the eastern Qinling orogen are located at the junction of the northeastern margin of the Tibetan Plateau, the North China Craton and the Yangtze Craton. They constitute the unique basin-range system with oil and gas, helium and geothermal resources. The Cenozoic is a key period related with the sedimentary-tectonic evolution of the Weihe Basin, the uplift of the Weibei uplift and the eastern Qinling orogen. However, the coupling relation of these processes remains poorly constrained, which hinder the understanding of distribution of regional mineral resources. The basin-range coupling is reflected in time, space, material, tectonism and earth surface morphology. We analyzed the range and rate of the tectonic subsidence based on a large number of borehole data via the “backstripping”, and restored the basin sedimentary evolution history according to the distribution of sedimentary thickness at the different stages during main settlement period. The results showed that the Cenozoic sedimentary-tectonic evolution of the Weihe Basin is characterized by migration from southwestern Xi’an depression to northeastern Gushi depression. There was a rapidly subsidence in the Weihe Basin during the Paleocene-Eocene, and then the Xi’an depression became the main depocenter and subsidence center at the Early-Middle Miocene. At the Late Miocene, both of the Xi’an and Gushi depressions became the main depocenter and subsidence center. During Late Pliocene to Early Pleistocene, the subsidence center migrated to the northeastern Gushi depression. Late Pleistocene, both of the Xi’an depression and Gushi depressions were in a rapid subsidence. The results of fission track dating indicated that the Weibei uplift experienced a rapid uplift during the period from ca. 45 Ma to ca. 32 Ma, which was synchronous with a ca. 57～40 Ma rapid uplift in the Taibai and Huashan Mountains. These uplifts are coupled with the ca. 40 Ma rapid subsidence of the Weihe Basin. The sustained rapid subsidence of the Weihe Basin from ca. 7.3 Ma in the Late Miocene was basically consistent with the rapid uplifts of the Weibei uplift at ca. 5 Ma, the Taibai Mountain at ca. 10～9.6 Ma and the Huashan Mountain at ca. 8～5 Ma. The basin-range coupling reported in this paper is possible influenced by the complicated geodynamic processes of the subduction of the Pacific plate, the ca. 55～45 Ma collision between the India and Eurasia plates and the long-range effect of the ca. 10～8 Ma uplift and extension of the Tibetan Plateau.
Key words:Isopach map/
Fission track/
Sedimentary-tectonic evolution/
Uplift and exhumation/
Basin-range relations/
Weihe Basin/
Weibei uplift/
Eastern Qinling orogen
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