兰州秦王川盆地形成和演化特征的初步研究

A PRELIMINARY STUDY ON FEATURES OF FORMATION AND EVOLUTION OF QINWANGCHUAN BASIN IN LANZHOU

通过对兰州市秦王川盆地东西二侧隐伏断裂的探测及区域河流阶地的对比 ,研究了该盆地的形成和演化特征 .结果表明 ,秦王川盆地形成于第三纪 .在中更新世晚期由于受东西二侧边界断裂挤压逆冲活动的影响而成为一个封闭式的断陷盆地 .中更新世晚期—晚更新世早期金强河及黑马圈河沿盆地二侧古河道穿过秦王川盆地 ,注入黄河 ,从而使盆地内堆积了较厚的冲洪积砂砾石层 .晚更新世晚期—全新世早期由于坪城盆地的持续抬升 ,河流改道 。

The results surveying non visible faults at east and west sides of Qinwangchuan basin and the comparison of terraces of rivers in the region indicate that the basin was formed in Neogene and became a close fault basin in late period of mid Pleistocene by the compression and thrust of faults at east and west boundaries of the basin. The Jinqianghe river and Heimajuanhe river flowed across the Qinwangchuan basin to the Yellow river along the ancient river course of two sides of the basin from late period of mid Pleistocene to early period of late Pleistocene and a thick layer of alluvial and diluvial sand gravel was formed in the basin.The basin became an arid one from late period of late Pleistocene to early period of Holocene by continuous rising of Pingcheng basin and change of the river bed.