摘要
以柴达木盆地西部尕斯库勒盐湖干盐滩6个钻孔岩芯为研究对象,从岩性特征、成盐期、沉积类型、沉积结构、沉积幅度等方面探讨尕斯库勒盐湖沉积特征。研究表明,自280 ka以来尕斯库勒盐湖经历相对湿润—干旱的气候波动和气候演化,在距今43.6 ka左右进入最干旱时期,可能属于柴达木盆地第二次成盐期;沉积结构层分异现象不明显;各成盐期平均沉积速率变化不大,平均沉积速率比新疆和内蒙古地区高;该湖沉积中心在盐湖的西北部。
Qaidam Basin develops nearly continuous, integrative and ultra-thick Quaternary sediment sequences. Sa- line lake deposits are the product of the physic-geographical and geological environments. This paper discussed the sedimentary characteristics of Gasikule Salt Lake where located in the northwestern margin of Qaidam Basin. Brine in the lake belong to magnesium sulphate subtype and halite was the mainly chemical sedimentation. From the studies on cores from 6 boreholes which distributed in the east playa area by the on-the-spot documentation and indoor studies, the lithological features, salinization periods, sedimentary type, sedimentary structure and sedimentary amplitude have been studied. The research work will be of great importance to study the evolution process of Qaidam basin and Gas- ikule Salt Lake. The results revealed that the sedimentary sequences of silt-beating medium and coarse halite and silt-bearing mud and clay were the main lithological features and sedimentary rhythm changes frequently in Gasikule Salt Lake. The o- verall trend is that dettital sediment ratio gradually increased from top to bottom, and evaporate salt layer decreased in boreholes. Sedimentary characteristics showed obvious difference in the non-salinization phase and salinization phase. These represent two different sedimentary environments, and also indicate the result of long-term salt lake evolution with gradually becoming dry climate conditions. The sedimentary types can be divided into three kinds of silt clastic sedi- ments, clay and silt deposition, and evaporates of epsomite gypsum halite respectively. The detrital sediments in Gas- ikule Salt Lake district showed relatively simple in lithologic features with mainly silt sandstone distributed in the up- per portion of the core. Clay and mud-beating sediments were widespread in the middle-lower portion of the core and mostly occurred in interstratified layers with evaporate deposition. But evaporate deposition was widely distributed at the top of each boreholes. The evaporite deposition was mainly halite while gypsum and epsomite were occurred as as- sociated component in sedimentation sequence in Gasikule Salt Lake area. Therefore, there exist not obvious variations between evapotite layer and clay-sih layers. The sedimentary amplitude of Gasikure Salt Lake was completely consist- ent with geosynclines-polycyelic sedimentary characteristics in western Qaidam basin. According to the salt lake sedi- mentary amplitude and duration of salinization time, the salinization deposition period had been divided into seven stage of saline deposition and seven relative humid epoch since Late Pleistocene. Average deposition rate in each peri- od of saline sedimentation had little variation and retained in around 2.5mrn/a. It is thus evident that Gasikule Salt Lake deposition rate on average is about 5 times than that of Xinjiang region, and 2.5 times of Inner Mongolia region. The difference of the deposition rate may be contributed by the dry climate and desertification in Western Qaidam Ba- sin than that of in Inner Mongolia and Xinjiang region since Late Pleistocene.
出处
《沉积学报》
CAS
CSCD
北大核心
2014年第1期85-92,共8页
Acta Sedimentologica Sinica
基金
核能开发科研技术研究项目"含铀盐湖铀富集条件和资源评价与开发技术研究"(编号:地HY230-1)资助
关键词
尕斯库勒盐湖
岩性特征成盐期
沉积类型
沉积结构
Gasikule Salt Lake
lithologic feature
salinization period
sedimentary type
sedimentary structure
