柴达木盆地察尔汗古湖贝壳堤剖面沉积地球化学与环境变化

通过对柴达木盆地察尔汗古湖贝壳堤剖面沉积物中总有机碳、有机质碳同位素及碳酸盐含量、碳氧同位素的分析, 并结合粒度数据, 将研究剖面所记录的古湖泊环境演化过程划分为5个阶段.其中254 (连续古湖泊沉积开始与第八层底部) ~210cm (距今39.7~35.8ka BP之间) 为湖泊发育期.210~185cm (距今35.8~33.6ka BP之间), 185~112cm (距今33.6~27.2ka BP之间) : TOC、CaCO₃含量较高、δ18 O值偏正, δ13 C_org偏负, Mz值较低, 反映了当时温度较高, 湖水水位较高; 而112~55cm (距今27.2~22.3ka BP之间) 和55~0cm (距今22.3~17.5ka BP之间) : TOC、CaCO₃含量较低、δ18 O值偏负, δ13 C_org偏正, Mz值较高, 表明了温度相对较低(但气候仍较温暖), 湖水水位较低, 湖泊处于退缩时期.其间分别在距今32.2~32.4ka BP、30.4~29.8ka BP和28.4~27.2ka BP出现了3次较大的退缩过程, 约22ka BP出现了一次气候突变.贝壳堤剖面揭示在39.7~18.5 14C ka BP之间柴达木盆地气候较温暖湿润, 形成高湖面.从18.2ka BP开始, 湖泊进入退缩阶段.到17.5ka BP快速形成盐壳, 高湖面持续历史结束. 

Sedimentation Geochemistry and Environmental Changes during Late Pleistocene of Paleolake Qarhan in the Qaidam Basin

Based on the analysis of TOC, CaCO₃, δ13 C_org, δ18 O, δ13 C of shell bar sediments in the Qaidam basin and the comparison with grain size, the environmental change of the studied section are divided into five stages.From 39.7 to 35.8 ka BP is the period of high paleolake level development.From 35.8 to 33.6 ka BP and 33.6 to 27.2 ka BP, TOC and CaCO₃ contents, δ18 O value are high, while δ13 C_org value and median size content are low, which reflects a warm-humid climate and high lake level.During 27.2-22.3 ka BP and 22.3-17.5 ka BP, both the temperature and the lake level are lower than that of previous stages (but the climate was still warmer and more humid than that of today).The lake level decreased between 32.4 and 32.2 ka BP, 30.4 and 29.8 ka BP, 28.4 and 27.2 ka BP.Generally speaking, the climate was warm and humid in Qaidam basin and the high lake level sustained between 39.7 and 17.5 ka BP.The lake retreated abruptly at 17.5 ka BP, with a very strong increase of evaporation which resulted in the salt formation and the decrease of the high lake level.