楚雄前陆盆地的改造变形

Deformation of Chuxiong Foreland Basin

云南省的楚雄盆地位于扬子板块西南缘,是古特提斯的金沙江—墨江洋在中三叠世碰撞关闭后,在哀牢山—红河碰撞造山带东北侧形成的中生代前陆盆地。盆地曾先后经历了2期不同性质构造作用的改造变形。第Ⅰ期发生于晚白垩世—始新世,是以哀牢山—红河碰撞造山带的隆升,并由南向北,向楚雄前陆盆地逆冲推覆作用为主,形成变形强度逐渐衰减的递进逆冲—褶皱变形带,以及伴随在推覆体旁侧的左行平移走滑断裂作用的改造;第Ⅱ期为渐新世末—中新世时期,随着印度板块与欧亚板块碰撞后的楔入与持续榨挤,楚雄盆地由近E-W的轴向被推挤为NW走向,并同时发生了右行平移和简单剪切为主的断裂作用改造,以及由南西向北东方向持续的逆冲—褶皱变形。

Locating in the southwestern margin of the Yangtze Plate, the Chuxiong Basin in Yunnan Province is a Mesozoic foreland basin formed in the northeast of the Ailaoshan-Honghe Collisional Orogenic Belt after the closing of the Jinshajiang-Mojiang Oceans of Paleo-Tethys during the Middle Triassic. The basin has experienced 2 stages of tectonic deformations. In stage I , from the Late Cretaceous to Eocene, the Ailaoshan-Honghe Colli- sional Orogenic Belt uplifted and thrusted from south to north to the Chuxiong Foreland Basin, resulting in pro- gressive inversion and fold deformation belt with decreasing deformation strength as well as sinistral strike-slip fault by the side of nappe. In stage II , from the end of Oligocene to Miocene, as the Indian Plate collided with the Eurasian Plate and kept wedging and squeezing, the axial of the Chuxiong Basin changed from EW to NW; meanwhile, fracture deformations such as right-lateral movement and simple shear took place, and the thrust- fold deformation from SW to NE happened.