受周期性湖平面升降控制的冲积扇—扇三角洲沉积体系——柴达木盆地阿尔金山前西段干柴沟组

Alluvial Fan-fandelta-lacustrine Sedimentary System Controlled by Lake-level Changes: Ganchaigou Formation (Tertiary), Front of Aerjinshan, Western Chaidamu Basin, China.

柴达木盆地阿尔金山前西段第三纪湖盆边缘斜坡带的渐新统和中新统表现为扇三角洲-湖泊与冲积扇-湖泊两种沉积体系的交替叠复。其形成归因于湖平面的周期性升降变化。沉积层序分析表明,湖平面变化控制了两种层序,湖面高位层序由扇三角洲—湖泊体系各序列组成;湖面低位层序则包含了冲积扇—湖泊体系各序列的内容。作者分析了在湖平面升降控制下湖泊边缘碎屑沉积体系的特点。

The fill sediments deposited on the lake margin slope during the Oligocene-Miocene, front Aerjin shan, western Chaidamu basin, were composed of the alluvial-lacustrine and fandelta-lacustrine sedimentary systems.The deposition of the two kinds of sedimentary system were controlled by the lake-level changes episodically. There are two types of sedimentary sequences. The sequence at high lake-level stand consist of fandelta- lacustrine system in which there are some important deposition microfacies such as fandeita plain ( lakeshore channel, subwater distributary channel and interchannel) , front fandelta (overflow deposits and front sheet sediments) and fandelta-front.The sequence at low lakelevel stand come from alluvial fanlacustrine system.Under the condition of basically balance between basin subsidience and sediments accumulation rate, replacement of the sedimantary systems was dependent on the lake條evel fluctuationes. Sedimentary processes of the fan delta and its fades distributary influenced by lake-level changes is different from ones of the fault depression basin margins. Relationship between alluvial fan and lacustrine at low lake-level stand is also distinguish from the normal facies model in addition to gravity flow deposits that originate from flood water channel.