四川盆地古近纪古风向恢复与大气环流样式重建

四川盆地白垩纪—古近纪发育了大量沙漠沉积,是恢复古风向与重建大气环流样式的宝贵证据.通过对四川盆地古近纪柳嘉组大型风成沙丘前积层倾向的系统测量,参照当时的古纬度、古方位及大气环流模式,恢复了四川盆地古近纪的古风向,重建了当时的大气环流样式.结果表明,四川盆地古近纪盛行西风,受西风带控制.结合前人的研究成果可以得出,四川盆地白垩纪早期由东北信风带控制,晚期由西风带控制,古近纪早期则继承了白垩纪晚期的大气环流样式,仍由西风带控制,其大气环流样式的转换大约发生在晚白垩世中期,至少在古近纪柳嘉组沉积时期,东亚季风尚未建立,四川盆地仍为行星环流控制.

The reconstruction of Paleogene wind direction and general atmospheric circulation style in Sichuan Basin, Southwestern China

A large amount of desert sediments were developed during the Cretaceous and Paleogene in Sichuan Basin which are valuable evidence for the wind direction and general atmospheric circulation style reconstruction. Based on measuring the foreset bedding dip directions of the large scale eolian dunes in the Paleogene Liujia Formation in Sichuan Basin, palaeolatitude, paleo-orientation and general atmospheric circulation model, the palaeowind direction and general atmospheric circulation style have been reconstructed in this paper. It is resulted that the Paleogene Sichuan Basin was prevailing westerlies and controlled by westerly belt. By integrating the existed results, it can be revealed that Sichuan Basin was controlled by north-east trade belt at first and later by westerly belt during the Cretaceous which was inherited from that of the Cretaceous during the Paleogene and the transformation of general atmospheric circulation style was occurred at about the middle Late Cretaceous. Meanwhile, it can be deduced that the eastern Asian monsoon system had not been founded and the planetary circulation was still controlling wind system over Sichuan Basin at least when the studied horizon was depositing.