全新世以来察尔汗盐湖沉积物的OSL年代学研究

OSL Chronology in Sediment of the Qarhan Salt Lake Since Holocene

察尔汗盐湖沉积物记录了柴达木盆地晚更新世以来的环境演化信息,但全新世以来沉积剖面的研究比较稀少且相关年代数据也比较缺乏。在察尔汗盐湖别勒滩区段东部,别勒滩区段西部和达布逊区段东部的沉积剖面中各发现2层细碎屑夹层,采集了相应的光释光样品,以研究察尔汗盐湖全新世时期的沉积年代。结果表明,察尔汗盐湖达布逊区段东部剖面(DBX)的2个碎屑层分别形成于6.2 ka(8.90 m)和2.8 ka(1.96 m),别勒滩区段东部剖面的2个碎屑层分别形成于2.9 ka(3.20 m)和0.9 ka(1.40 m),别勒滩区段西部剖面的2个碎屑层分别形成于2.4 ka(3.10 m)和0.7 ka(1.50 m)。由于晚第四纪盐湖沉积松散且易溶造成样品的成分及来源复杂等影响,造成了剖面OSL数据远小于14C、U-Th测年数据(8~9 ka)。3个剖面沉积速率计算表明,察尔汗盐湖达布逊区段沉积速率大于别勒滩区段,而别勒滩区段东部的沉积速率高于西部,察尔汗盐湖与东台吉乃尔盐湖的沉积速率整体上保持一致。

The Qarhan Salt Lake sediments record the environmental evolution of the Qaidam Basin since the Late Pleistocene,but sedimentary profiles since the Holocene are relatively scarce and chronological data are lacking.Two fine-clastic intercalations were found in each of the sedimentary sections of Beletan,Beletan West and Dabuson sections of the Qarhan Salt Lake,and corresponding photoluminescence samples were collected to study the age of sedimentation in the Qarhan Salt Lake during the Holocene.The results show that the two clastic layers in the Dabuson(DBX)section of Qarhan Salt Lake were formed at 6.2 ka(8.90 m)and 2.8 ka(1.96 m),respectively,while those in the Beletan section were formed at 2.9 ka(3.20 m)and 0.9 ka(1.40 m),and those in the Beletan West section were formed at 2.4 ka(3.10 m)and 0.7 ka(1.50 m).The Late Quaternary Salt Lake sediments are loose and soluble causing the samples to be complex in composition and origin,resulting in the profile OSL data being much smaller than the 14C and U-Th dating data(8~9 ka).The sedimentation rates(from the bottom clastic layer to the surface layer)calculated for the three profiles indicate that the sedimentation rate in the Dabuson section of the Qarhan Salt Lake is greater than that in the Beletan section,while the sedimentation rate in the eastern part of Bele-tan is higher than that in the western part.The sedimentation rates in the Qarhan Salt Lake and the Dongtai Genel Salt Lake are generally consistent.