高精度光释光测年揭示的晚第四纪毛乌素和浑善达克沙地沙丘的固定与活化过程

利用光释光测年技术对毛乌素沙地和浑善达克沙地7个地点的沉积剖面进行了年代测试,结合地层特征,获得了最近60kaBP以来两个沙地沙丘固定与活化时间的年代学控制60kaBP以来毛乌素沙地的固定期分别为距今37.71ka、8.54ka、8.32ka、7.93ka、7.77ka、7.57ka、7.39ka和2.39ka以后;活化的时间分别为距今57.08ka、52.50ka、13.65ka、13.13ka、7.20ka前后、2.39ka以前和0.29ka以来。在10.97kaBP、10.04kaBP、9.81kaBP和8.67kaBP前后沙地处于气候干湿交替时期。全新世期间,浑善达克沙地在距今8.74～8.72ka、7.79ka前后,沙丘活化;5.69kaBP、4.25kaBP、2.75kaBP、1.53kaBP和0.71kaBP前后,沙丘处于相对固定阶段,0.15kaBP以来,沙丘处于半固定状态。晚第四纪气候千年至百年尺度的变化可能是两个沙地沙丘活化与固定的主导因素。

Active and Inactive Phases of Sand-dune in Mu Us and Otindag Sandlands during Late Quaternary Suggested by OSL Dating

The loess-desert transition zone in north China is sensitive to reflect climate changes, and it is one of the key sites to investigate the history of past environmental changes. Optical stimulated luminescence dating (OSL) has been used to obtain the ages of seven profiles in Mu Us and Otindag sandlands. All the sediments are aeolian originations. Our results provide chronology constrain to active and inactive phase of sand dunes in the two sandlands during the past (60 000) years: the sand dunes are stable at 37.71 ka BP, 8.54 ka BP, 8.32 ka BP, 7.93 ka BP, 7.77 ka BP, 7.57 ka BP, 7.39 ka BP and late 2.39 ka BPin Mu Us sandland, and paleosol were developed. Whereas, the sand dunes are mobile at around 57.08 ka BP, 52.50 ka BP, 13.65 ka BP, 13.13 ka BP, 7.20 ka BP and 2.39 ka BP. In Otindag sandland, the moveable phases of sand dunes took place at 8.74~8.72 ka BP and 7.79 ka BP respectively, the inactive periods occurred at 5.69 ka BP, 4.25 ka BP, 2.75 ka BP, 1.53 ka BP, 0.71 ka BP and 0.15 ka BP to now, the sandland is dominaued by semi-stabilized sand dunes. Though the active and inactive phases in Mu Us and Otindag sandlands are not always at the same time, the changes are consistent with variations of the East Asia monsoon.Furthermore, there are two samples whose single-aliquot De values are likely scattered distribution to some extent, possibly because of heterogeneous variations in microdosimetry and biodisturbing during burial of the sediments, or there is water reworking on the aeolian deposit.