青藏高原东南缘川滇地块古近纪沉积地层古地磁分析及其构造意义

摘要

针对中国西部及中亚地区以红色陆相沉积岩为主的白垩纪—新生代地层中普遍存在古地磁数据磁倾角偏低的现象，对青藏高原东南缘川滇地块中部大姚地区古近纪陆相红层进行了磁倾角偏低研究。实验结果表明，川滇地块内部古近纪陆相红层古地磁数据不存在明显的磁倾角偏低的现象。结合前人对川滇地块内部古地磁数据及周缘新生代走滑断裂的活动演化历史研究，确定川滇地块自中中新世以来川滇地块内部表现为刚性旋转，楚雄地区则发生局部构造旋转叠加。%A paleomagnetic experiment was carried out on Paleocene red beds of Dayao basin in Chuan-Dian Fragment for studying the common phenomenon of inclination shallowing in western China and Central Asia. Paleomagnetic researches demonstrate that in⁃clination shallowing of Paleogene red beds does not obviously exist in the study area. Combined with previous paleomagnetic studies and Cenozoic peripheral fault structures, the authors hold that Chuan-Dian Fragment has rotated as a rigid block with a little south⁃ward escape since middle Miocene, though magnitudes of tectonic rotation are significantly different in Chuxiong area, where there has occurred local structural rotation superimposition.