晚第四纪柴达木盆地盐湖成盐期与冰期对比方案的再认识

文章以柴达木盆地察汗斯拉图、昆特依和一里坪盐湖共计6个中更新统—全新统含盐地层剖面为研究对象,通过铀系测年和光释光测年测定其成盐年代,利用X射线衍射分析测定其盐类矿物种类。察汗斯拉图D19剖面芒硝和石盐层的铀系年代为(231.5±19.5)～(239.5±40.4)ka BP,对应于深海氧同位素阶段(MIS)7早期;昆特依KP4剖面芒硝和石盐层的铀系年代为(76.8±19.7)～(53.7±6.5)ka BP,其中,芒硝沉积的年代可以对应于末次冰期早冰阶MIS 4;察汗斯拉图D13剖面钾盐和石盐地层的光释光年代为(6.6±1.0)～(2.6±0.4)ka BP,对应于MIS 1;一里坪YP3剖面石盐地层的铀系年代为(6.2±2.7)～(2.7±1.1)ka BP,对应于MIS 1,但测年误差较大。一里坪YP2剖面和昆特依KP2剖面未能得到有效的测年数据,测年失败的主要原因是剖面样品受到卤水开采和输卤的影响。研究表明,柴达木盆地西部盐湖存在MIS 7早期和MIS 4的芒硝和石盐层,而在MIS 1有固体钾镁盐沉积。盆地西部盐湖在MIS 8、MIS 6、MIS 4和MIS 2有芒硝沉积,芒硝...

Rethinking on correlation scheme between Late Quaternary evaporite-deposition period and glacial period in saline lakes of Qaidam Basin

Six middle Pleistocene-Holocene evaporite-bearing profiles in saline lakes (namely Chahansilatu, Kunteyi and Yiliping) of the western Qaidam Basin were taken as study objects. The U-series dating and optically stimulated luminescence (OSL) dating were applied to obtain the evaporite depositional age, and X-ray diffraction was applied to identify the evaporite minerals. Based on the geochronology and evaporite mineralogy data, this paper discussed the relationship between evaporite deposition period and glacial period in the Qaidam Basin.The U-series age of mirabilite and halite layer in D19 profile of Chahansilatu is (231.5±19.5)~(239.5±40.4) ka BP, corresponding to marine oxygen isotope stage (MIS) 7. The U-series age of mirabilite and halite layer in KP4 profile of Kunteyi is (76.8±19.7)~(53.7±6.5) ka BP, in which the deposition age of mirabilite correspond to the early stage of the last glaciation MIS 4. The OSL age of potash and halite strata in D13 profile of Chahansilatu is (6.6±1.0)~(2.6±0.4) ka BP, corresponding to MIS 1. The age of U-series in YP3 profile of Yiliping is (6.2±2.7)~(2.7±1.1) ka BP, corresponding to MIS 1, but with large dating error. The age dating work of YP2 profile in the Yiliping and KP2 profile in the Kunteyi were failed. The main reason for the failure was that the samples of the profile were affected by brine mining and brine transportation. This study indicates there were mirabilite-dominated evaporite deposits during MIS 7 and MIS 4, while in the MIS 1, there were potash deposit. There are mirabilite deposits during MIS 8, MIS 6, MIS 4 and MIS 2 in saline lakes of the western Qaidam Basin, and there is correlation between mirabilite-deposition period and glacial period. Combined with the previously reported data of the saline lake in the late Quaternary, the correlation scheme between the evaporite-deposition period and glacial period of the saline lake in Qaidam Basin was improved, and the correlation scheme since MIS 6 was extended to MIS 8. The Late Quaternary glacial environment is conducive to the mirabilite-dominated evaporite deposition in the Qaidam Basin.