摘要
文章以厚度10 m的青海湖地区大水溏剖面(QDST)为研究对象,利用CM-5分光测色计测得232个土壤样品的色度参数(a*、b*、L*),分析了土壤色度变化特征,辅以SC/D(粒度敏感指标)、磁化率、Rb/Sr、CO32-等指标并结合OSL测年,恢复了近32 ka以来青海湖地区的环境演变过程。结果表明:1)a*、b*自剖面底部向上呈波动式先减小后增大再减小态势,均大致呈下层古土壤高于上层古风成砂,高值示温湿气候;L*自剖面底部向上先急剧减小后微升,且大致呈下层古土壤略低于上层古风成砂,高值示冷干气候;2)a*、b*与磁化率、L*与Rb/Sr均呈显著负相关,L*与碳酸盐呈显著正相关且与SC/D值变化态势一致;3)剖面CO32-均值达8.74%,且CO32-峰区与L*高值区吻合度高,对L*的贡献较大,L*可反映不同沉积层形成时期的降水量;4)近32 ka以来青海湖地区经历了温湿→冷润→温润→凉干→温润→温湿→凉干→温凉→冷干的环境演变过程,进一步可划分为:a*较高、b*最高、气候整体较为温湿的末次冰期间冰阶(32.0~23.3 ka);a*和b*低、L*较高、气候整体偏冷润的末次冰盛期(23.3~15.2 ka);a*和b*较低、L*最低、气候整体温凉偏湿的末次冰消期(15.2~10.4 ka)以及a*和b*整体较高、L*整体较低、冷暖波动频繁的全新世(10.4 ka至今)。
In order to explore the significance of the sedimentary environment recorded by the soil chroma,to make chromaticity studies more useful to Quaternary environmental researches,and also to enrich the available surrogate indexes of paleoenvironmental changes in northeastern Qinghai-Tibetan Plateau,this study investigate an exposed profile(Dashuitang section)in an aeolian sand dune that lies in the east lake margin of Qinghai Lake.The Dashuitang section(QDST:36°49.701'N,100°51.557'E;3450 m above sea level)is 10 m thick.The sampling strategy was based on the observed morphological characteristics of the profile,and the samples were taken at 10 cm,5 cm,2 cm and 5 cm intervals for the 0.3~3.7 m,3.7~5.3 m,5.3~7.6 m and 7.6~10.0 m sublayers,respectively.A total of 232 regular soil samples were collected.Meanwhile,10 samples were collected from the top and bottom of each sublayer,namely the transition portions between soil layer and aeolian sand layer were dated by OSL dating.The stratigraphic age since 31.9±1.3 ka was covered by the 10 m profile.After sample pretreatment,three colorimetric parameters(a*,b*,L*)were measured by CM-5 spectrophotometer,the grain size was measured by Malvern 2000 laser particle size analyzer,the element was measured by Philips Panalytical Magix PW 2403 X-ray fluorescence spectrometer,and the magnetic susceptibility was measured by Bartington MS-2 magnetic susceptibility meter.Based on the analysis of the characteristics of soil chromaticity changes,supplemented by magnetization,SC/D,CO32-,Rb/Sr and other indicators and combined with OSL dating ages,the environmental changes of Qinghai Lake area since nearly 32 ka was restored.The results show that:(1)From the bottom of profile upwards,a*and b*firstly decreased then increased and finally decreased again.They all show that the values of paleosol layer are higher than the aeolian sand layer,and the high value indicats a warm and humid climate.From the bottom of profile upwards,L*decreased sharply and then increased slightly,and show that the
作者
胡梦珺
李娜娜
张亚云
王佳
李春艳
Hu Mengjun;Li Nana;Zhang Yayun;Wang Jia;Li Chunyan(College of Geography and Environmental Science,Northwest Normal University,Lanzhou 730070,Gansu)
出处
《第四纪研究》
CAS
CSCD
北大核心
2020年第5期1105-1117,共13页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:41171018、40761026和41161036)资助。
关键词
土壤色度
青海湖
古风成砂-古土壤
环境演变
soil color
Qinghai Lake
aeolian sand-paleosol
environmental evolution
