青海湖的地质构造背景及形成演化

GEOTECTONIC SETTING, FORMATION AND EVOLUTION OF THE QINGHAI LAKE

青海湖地区位于 3个构造单元及多条深断裂的交汇部位 ,结构复杂 ,强度较弱。上新世出现断陷 ,中更新世成湖。湖盆可划分为 3个地垒和 3个次级断陷盆地。其形成和演化受中祁连南缘大断裂带、宗务隆山 -青海南山大断裂带和黑马河 -达日大断裂带重新活动及其它NWW ,NW ,NNW ,SN ,NE向断裂的活动及伴随的差异隆升所控制 ,与青藏高原的隆升演化有密切关系 ,尤其是可能与青藏高原发生后造山伸展作用有关的应力场转变造成的负反转构造有重要关系。中中新世夷平面形成以来的新构造活动和青海湖的形成演化具明显的脉动性。中中新世以来的新构造活动可分为 5个阶段 ,青海湖形成演化过程可大致分为 9期。

The Qinghai Lake area is situated at the juncture of 3 tectonic units and several deep faults, so tectonic deformafion is exfensive there. Fault depression took place in Pliocene and the Qinghai Lake formed in Middle Pleistocene. The Lake basin can be divided into 3 horsts and 3 second-order fault basins. The formation and evolution of the Qinghai Lake had been mainly controlled by removement of south marginal large fault belt of Middle Qilian block, ZhongwulongshanQinghainanshan large fault belt and HeimaheDari large fault belt, the movement of faults with strikes in NWW, NW, NNW, SN and NE, and regional differential uplifting as well. Its formation and evolution had close relationship with uplifting of Qinghai-Tibet plateau, especially with negative inversion structure formed by change of stress field in Middle Pleistocne. Since the formation of Middle Miocene leveling plane, the neotectonism and the formation and evolution process of the Qinghai Lake are characterized by obvious pulsation. Since Middle Miocene, neotectonic activities over Qinghai Lake area can be divided into 5 periods, and the formation and evolution of the Qinghai Lake can be divided into 9 stages.