摘要
对天山内部大型断裂带晚第四纪以来变形特征的研究是认知天山现今构造变形特征的重要途径.在大比例尺遥感影像解译的基础上,利用野外调查测量、探槽开挖及热释光测年的方法,对那拉提断裂进行了研究.那拉提断裂是一条晚第四纪以来仍有较强活动的大型逆冲左旋走滑断裂带,断裂带宽度巨大,由多条倾向不同的次级断裂组成,分布在南北宽数公里的范围内,这些滑动面是逆冲走滑断裂在地表分散形成的“正花状”构造.晚第四纪期间,那拉提断裂曾多次发生过断错地表的强震事件,是天山内部一条重要的地震构造带.断裂断错了那拉提山前晚第四纪以来的各级地貌面,主要表现为断层陡坎、冲沟水系和地貌面的左旋位移,根据实测陡坎高度和对应地貌面的定年,获得断裂所造成的南北向地壳缩短速率在0.8～1.1mm/a左右,表明天山内部同样存在明显的构造变形.结合目前已有的地震地质研究资料,对天山山前和天山内部吸收的变形量分配进行了讨论,认为天山南北两侧山前对变形量的吸收调节作用并不显著高于天山内部.那拉提断裂具有左旋走滑特征的发现,对于理解天山现今变形方式以及应变分配具有重要的意义.
The Late-Quaternary deformation characteristics of the large faulting zones extending through interior mountains are critical to understanding the crustal deformation of the Tianshan Mountains.Based on large-scale remote sensing image interpretation,field survey measurements,trenching and thermoluminescence dating on the Nalati fault,a major faulting zone within interior Tianshan,we obtained the slip parameters to unveil the kinematic features of this fault.The results show that on this fault strong motion since Late-Quaternary occurred with dominant thrust accompanied by sinistral strike-slip.The fault zone is composed by a number of secondary faults with different tendencies distributing in a swathe transvesely ranging several kilometers from south to north.These secondary faults are ＂positive flower structure＂ that branches from the main fault at depth and spreads to the surface.The constant re-occurrences of outrcropping co-seismic ruptures imply that the Nalati fault is an important seismogenic structure of the interior Tianshan in Late-Quaternary period.On the Nalati Hill piedmont,this fault sinistrally dislocated the Late-Quaternary geomorphic units including fault scarps,gullies,and landforms.As shown by fault throw measurements and the dating of corresponding units,the Nalati fault contributes to the south-north trending crustal shortening at the rate of about 0.8～ 1.lmm/a,which suggests that obvious deformation exists in the interior of the Tianshan Mountains.Related to previous geological studies,the balance of crustal deformation across the Tianshan Mountains is further discussed and the results suggest that the piedmonts on both sides of the Tianshan Mountains may possibly accommodate more crustal deformation than the interior Tianshan does,while the exceeding accommodation could not be significant.The new discovery of sinistral strike-slip on the Nalati fault has important tectonic meaning which calls for deep consideration of strain distribution along the Tianshan Mountains.
出处
《第四纪研究》
CAS
CSCD
北大核心
2014年第2期269-280,共12页
Quaternary Sciences
基金
国家青年自然科学基金项目(批准号:41102137)资助
关键词
天山
那拉提断裂
晚第四纪
运动特征
构造变形
Tianshan Mountains
Nalati fault
Late-Quaternary
kinematic features
tectonic deformation
