柴西南阿拉尔地区古近纪—新近纪地层结构及环境特征

Stratigraphic Structure and Environmental Characteristics of Paleogene-Neogene in Alaer Area, Southwestern Qaidam Basin

为研究阿拉尔地区古近纪—新近纪地层结构及环境特征,在野外岩芯观察和描述的基础上,对研究区地层结构类型进行划分和形成机理解释,识别出各时期地层结构类型并结合古生物特征,最终进行环境特征综合分析。结果表明:地层结构包括均质型和非均质型(互层式、夹层式、进积型、退积型和无序多层式);各地层结构的形成与沉积物供给速率同可容空间速率之间的对比差异有关;下干柴沟组—下油砂山组时期识别出扇三角洲平原和滨浅湖2种沉积亚相及部分微相类型,表现为扇三角洲平原和滨浅湖交替沉积,湖平面多次升降旋回,气候经历了温凉干旱—暖热—半干旱—干旱加剧,水体逐渐咸化,沉积环境由还原转向氧化。

In order to study the stratigraphic structure and environmental characteristics of Paleogene-Neogene in Alar area, we, based on the observation and description of the field core, think that the stratigraphic structure types of the study area were divided and the fomlation mechanism was explained in this article. The types of stratigraphic structures in each period were identified and the paleontological features were identified, and the environmental characteristics were synthetically analyzed. The results show that the stratigraphic structure includes homogeneous and heterogeneous （interbedded, intercalative, progradational, retrogradational, and disordered ）. The formation of various types of stratigraphic structures is related to the comparison between the rate of sediment supply and capacitive space. We know that 2 sedimentary subfacies-fan delta plains and shore shallow lakes as well as partial microfacies were identified in the period of the Lower Ganchaigou Formation-Xiayoushashan Formation, which expressed as alternating fan delta plains and shore shallow lakes. The lake level has undergone several cycles of ups and downs, and the climate has experienced cool and dry-warm heat-semiarid-drought intensification. The water body is gradually salted and the sedimentary environment has turned from reduction to oxidation.