【摘要】 基于野外和钻孔测井资料分析、火山岩同位素年代学分析(40Ar-39Ar和SHRIMP U-Pb法)、地震剖面的构造解释、断层运动学的野外分析结果,综合研究了胶莱盆地及其邻区白垩纪—古新世沉积构造演化历史。岩性地层分析表明,胶莱断陷盆地由三套地层单元所充填:早白垩世莱阳群和青山群、晚白垩世—古新世王氏群。青山群火山岩的同位素年代学测试结果给出了该火山岩的喷发时代在120~105Ma。地震剖面的构造解译结果揭示胶莱盆地伸展构造受到深部两个拆离构造系统控制:一个发育于盆地南部地区,拆离断面位于深部8~10km,向南缓倾于苏鲁造山带之下;另一个拆离系统由一系列北倾的犁式断层组成、分布于宽阔的胶莱盆地北部地区,主拆离面向北倾。这两个拆离系统分别形成于早白垩世莱阳群和晚白垩世—古新世王氏群沉积阶段。通过对不同地层单元断层滑动矢量的野外测量和古构造应力场反演,以及地层时代和同位素年代学测试结果的制约,建立了白垩纪—古新世构造应力场演替的年代序列。结果表明,胶莱盆地在白垩纪—古新世之间经历了伸展—挤压应力体制的交替演化。早白垩世伸展作用经历了两个不同的阶段:早期NW—SE向伸展和晚期近W—E向伸展。在早白垩世末期至晚白垩世初期,盆地遭受NW—SE向挤压,导致了胶莱盆地的缩短变形和郯庐断裂带的左旋走滑活动。晚白垩世—古新世时期,构造应力场转变为N—S向伸展,直到古新世末期,构造应力场转换为NE—SW向挤压。胶莱盆地和沂沭裂谷系白垩纪—古新世沉积构造演化历史对华北地区岩石圈减薄过程的动力学背景提供了重要的构造地质学制约。笔者推断,早白垩世两期引张应力作用是分别对华北地区增厚地壳或岩石圈的重力垮塌和岩石圈拆沉的响应,而早白垩世末期NW—SE向挤压记录了古太平洋板块与亚洲陆缘俯冲碰撞产生的远程效应。晚白垩世—古新世的引张伸展作用完全不同于早白垩世伸展构造,它指示了沿NNE向郯庐断裂带的右旋走滑活动及其拉分作用,在动力学上受到青藏地区块体的陆—陆碰撞产生的远程效应和古太平洋板块向亚洲大陆俯冲作用的联合应力场控制。更多还原

【Abstract】 This paper deals with tectono-sedimentary evolution of the Jiaolai basin (North China) from Cretaceous to Paleocene, based on field observation, logging and lithostratigraphic, isotopic (40Ar-39Ar and SHRIMP U-Pb) data of the volcanic rocks, and structural interpretation of seismic profiles. Lithostratigraphic analysis shows that the Jiaolai basin is a faulted basin filled with three distinct rock units: the Early Cretaceous Laiyang and Qinshan groups and the Late Cretaceous to Paleocene Wangshi Group. Isotopic dating of the volcanic rocks of the Qingshan Group yields ages of 120 ～100 Ma. Structural interpretation of seismic profiles reveals that the extensional structure of the Jiaolai basin is confined by two deep seated detachment systems: one developed to the south basin and its detached plane is about 8～10 km beneath the surface, gently dipping southwards underneath the Sulu orogenic basement; the other consists of a series of N-dipping faults, which are developed around the northern area of the Jiaolai basin, with the major fault plane N-dipping. The both WERE formed during depositional stages of the Early Cretaceous Laiyang Group and Late Cretaceous Wangshi Group. Fault slip vector data measured from different rock units of the basin, combined with stress regimes, stratigraphic epochs and isotopic dating, helps US to establish the chronology of the Cretaceous to Paleocene tectonic regimes. The results show that the Jiaolai basin underwent alternation of extension and compression during the Cretaceous and Paleocene. The Early Cretaceous extension experienced two phases: the early NW-SE extension and the late W-E extension. This was followed by a NW-SE compression occurring at the end of Early Cretaceous to the early Late Cretaceous (about 90±5 Ma). This compression resulted in shorting of the Jiaolai basin and sinistral slip of the Tan-Lu fault zone. Tectonic regime transformed to N-S extensional one during Late Cretaceous to Paleocene, and ended by a NE-SW compression at the end of Paleocene. This Cretaceous to Paleocene tectono-sedimentary evolution of the Jiaolai basin and the Yi-Shu rift zone provides constraint on geodynamic settings of the lithosphere thinning processes underneath North China. From above-mentioned it is concluded that the two extensional phases in Early Cretaceous were dynamically associated with either gravity collapse or lithospheric delamination of the thickened crust or lithosphere in North China and the NW-SE compression records the long-distance effect by the subduction of paleo Pacific plate towards the bottom of the Asian continent. Different from above-mentioned one, the Late Cretaceous to Paleocene extension was a dextral strike slip along the NNE-striking Tan-Lu fault system and its pull-apart, which were geodynamically controlled by joint stress fields resulted from far-distance continental collision of the Qinghai-Tibet blocks and the subduction of the paleo pacific plate towards the Asian continent.更多还原