柴达木盆地鸭湖地区水上雅丹地貌成因研究

Research on the Genesis of Semi-submerged Yardang Landform in the Duck Lake Area of Qaidam Basin

本文通过对青海柴达木盆地鸭湖地区构成水上雅丹的地层序列和沉积相、地层形成时代、地层形成后演化为雅丹地貌的构造条件、气候条件和人为因素的研究,认为构成研究区水上雅丹的地层为中新世上油砂山组,所含介形虫组合指示其形成时代为中新世晚期;沉积相和孢粉组合分析揭示本区在中新世晚期为温暖干旱的气候下的古湖环境,接受湖相和湖泊三角洲前缘沉积;上新世在区域构造抬升和干旱化气候的双重作用下,古湖逐渐萎缩;更新世在极端干旱和强劲的季风环境中,被抬升到地表的上油沙山组上部地层在风蚀为主的外营力作用下形成雅丹;晚更新世末期—全新世由于末次间冰期的到来,气候转向温暖湿润,湖水再次入侵。近年人类活动改变了湖泊分布格局,导致湖泊淹没了部分陆地上的雅丹,呈现为奇特的水上雅丹地貌景观。

Through the study of the stratigraphic sequence,sedimentary facies,formation age of the strata that make up Semi-submerged Yardang landform and the tectonic conditions,climate and human factors of the evolution of Yardang landform after the formation of stratigraphic in the Duck Lake area of Qaidam Basin in Qinghai Province,the formation of Semi-submerged Yardang landform in the study area is the Miocene Upper Youshashan Formation,and the ostracod assemblages indicate that the formation age is late Miocene. The analysis of sedimentary facies and sporo-pollen assemblages reveal that this area was warm and arid climate in late Miocene and it was covered by the ancient lake and accepted lacustrine facies and lacustrine delta front facies sedimentary. In the Pliocene,the ancient lake shrank and disappeared under the dual role of regional tectonic uplift and arid climate.Pleistocene in extreme drought and strong monsoon environments,the upper strata of the Upper Youshashan Formation was lifted up to the surface,formed Yardang landform under the action of wind erosion-dominated external forces. From late Pleistocene to early Holocene due to the arrival of the last interglacial,the climate turned warm and moist,and the lake invaded to form three lakes. In recent years,the distribution pattern of lakes has been changed under the action of human activities,which presents the landscape of today＇s Duck Lake. Today,the lake area of Duck Lake drowns some Yardang and becomes a peculiar Semi-submerged Yardang landform landscape.