【作者】 王亮；

【导师】 肖安成； 陈汉林；

【作者基本信息】 浙江大学 ， 构造地质学， 2009， 博士

【摘要】 阿尔金断裂是青藏高原北部的边界断裂,同时也是柴达木盆地的西北部边界,新生代阿尔金断裂的活动控制了柴达木盆地西部的盆地填充和早期构造带的形态。针对柴达木盆地西部、靠近阿尔金山的沉积层序和构造活动特征等方面的研究,必定能够进一步发展和完善对阿尔金断裂带的研究和认识。本文根据“盆山耦合”的思想,从柴达木盆地受阿尔金构造活动制约这一特征出发,利用逆向推理的思路,利用盆地记录来反演造山带的大地构造过程,力图重建新生代阿尔金断裂的阶段性过程和重要的构造演化特征。在综合利用实测地面地质、地球物理和钻井资料的基础上,通过研究发现在柴达木盆地西部地区的新生代层序内部存在着两个重要的,与阿尔金断裂的活动性相关的角度不整合面,它们分别位为上、下干柴沟组之间和上、下油砂山组之间。通过综合完成的多条位于阿尔金山南侧的区域剖面、不同时期的沉积相和古构造分析的研究,证实了这两期不整合的平、剖面分布,为在空间上论证新生代阿尔金断裂的影响范围,以及其时间上的阶段性活动特征提供了依据。研究指出,新生代早期的阿尔金断裂带以形成大范围的古隆起为标志,隆起区遭受剥蚀,从而产生了上、下干柴沟组之间的角度不整合面;晚期古隆起活动的继续、挤压应力的聚集,导致现今意义上的阿尔金断裂的发育,断裂让挤压应力获得释放,构造隆升速率开始降低,甚至停止,其结果导致新沉积地层的超覆进积和上、下油砂山组之间角度不整合面的产生。两期不整合仅局限于阿尔金山断裂南侧,呈带状分布。基于以上研究思想的形成,完成了阿尔金断裂带新生代的多阶段、不同性质的构造演化模型,来说明这一综合的构造演化历史。渐新世晚期开始,阿尔金地区开始大范围隆升;至中新世中期,隆升速率减小,阿尔金断裂带开始大规模走滑活动;之后,持续发生多期走滑活动。这些研究为研究阿尔金断裂新生代的活动时间与活动性质以及柴达木盆地新生代演化提供了新的限定,从盆地构造变形和沉积记录的角度探讨造山带演化,为阿尔金与柴达木地区盆山耦合研究提供了新例证。更多还原

【Abstract】 The Altyn Tagh fault constrains the north margins of the Tibetan Plateau, and also delimits the northwest of the Qaidam basin. The Cenozoic activity of the Altyn Tagh falut controlled the deposition and structures of the west Qaidam basin. This study, which focuses on the sedimentary sequences and structural characteriscs, will provide new constraints for the evolution of the Alytn Tagh fault.The idea of coupling between orogen and basin has been applied to this study. The Cenozoic structural deformation and deposition in the Qaidam basin have been used to reveal the evolution of the Altyn Tagh orogen.Based on the geological survey, synthesis of geophysical and drilling data, two unconformities, between upper and lower Ganchaigou Formation and between upper and lower Youshashan Formation, respectively, have been discovered in the west Qaidam basin, which have been considered to relate to the activity of the Altyn Tagh fault. The analysis of regional cross sections, sedimentary facies and paleo-structures in the south Altyn Tagh fault reveal the distribution of those two unconformities, which provide constraints for the spatial impact and active timing of the Altyn Tagh fault.The formation of large-scaled uplift marked the early Cenozoic activity of the Alyn Tagh fault. The erosion of the uplift area yielded the unconformity between upper and lower Ganchaigou Formation. The present Altyn Tagh fault was formed by later stage of uplift. During this stage, the activity of faults released the compressional stress, which slowed down the uplift rate to even cease uplifting. Sequentially, new deposit overlapped the older, and the unconformity between upper and lower Youshashan Formation formed as well during this stage.The discoveries above provide implications for the Cenozoic evolution model of the Altyn Tagh fault as followed. Since late Oligocene, large-scaled uplift occurred around the Altyn Tagh area, till mid-Miocene, the uplift rate slowed down, and the activity of the Altyn Tagh fault displayed as strike-slipping. Lately, stages of strike-slipping prevailed this area.These results provide new constraints for the active timing and characteriscs of the Altyn Tagh fault and Cenozoic evolution of the Qaidam basin. The research method, using the basin record to reveal the orogen evolution, provides new example for basin-orogen coupling between the Altyn Tagh fault and the Qaidam basin.更多还原