Paleoenvironmental Change at Desert-loess Transitional Zone in Salawusu River Valley During MIS 2 Stage of Last Glacial Period(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2017年第04期
- Page:
- 551-562
- Research Field:
- 水资源与环境
- Publishing date:
Info
- Title:
- Paleoenvironmental Change at Desert-loess Transitional Zone in Salawusu River Valley During MIS 2 Stage of Last Glacial Period
- Author(s):
- ZHANG Cheng-jun; ZHANG Wan-yi; ZHANG Li; ZHANG Jing-ya; CHENG Ming-ming; WANG Xiao-yu; LI Bao-sheng
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1. School of Earth Sciences, Lanzhou University, Lanzhou 730000, Gansu, China; 2. Key Laboratory of Mineral Resources in Western China (Gansu Province), Lanzhou University, Lanzhou 730000, Gansu, China;3. School of Geography, South China Normal University, Guangzhou 510631, Guangdong, China
- Keywords:
- last glacial period; MIS 2 stage; limnetic facies; n-alkane; carbon and oxygen isotopes; westerly jet; summer monsoon; Salawusu river valley
- PACS:
- P534.63
- DOI:
- -
- Abstract:
-
Temperature decreases all the world, and summer monsoon in China retreats towards south with winter monsoon strengthened in the last glacial period. Under this palaeoclimatic background, the aeolian activity is intensified in the northern China, and sea-level declines in South China Sea, and lake shrinks. Oppositely, there are several obvious limnetic facies and river facies strata in Salawusu river valley along the desert-loess transition zone in the southern part of Mu Us Desert, which is at the boundary of modern monsoon. Grain size, total organic carbon (TOC), carbon and oxygen isotopic compositions and organic biomarker n-alkane (m/z is 85) of sediment at Milanggouwan section since MIS 2 stage (6.0-16.5 m, 11-30 ka BP) were analyzed. The results show that the sediment in limnetic facies is made up of the sandy silt, and the mean is 4.5 Φ or so; the sediment in the paleosol strata is made up of muddy silt, and the mean is more than 5 Φ; the sediment in the river facies is made up of silty sand, and the mean is about 3 Φ; total organic carbon is 0.1%-1.0% with the average of more than 0.5% in the limnetic and paleosol facies sediments; total organic carbon is lower in the river facies sediments(0.01%-0.10%); there is an incomplete forest steppe during 23-29 ka BP with n-alkane C27, C29, C31 preponderance; forest steppe and fresh water lake with a long residence time during 17-19 ka BP are inferred by the high contents of n-alkane C27, C29, C31, and the contents of n-alkanes with low carbon number and middle carbon number increase; 19-23 ka BP is the last glacial maximum in this area with a strongest aeolian activity under the coldest and driest condition; desert steppe and dispersal lakes and ponds along the river in Middle Holocence from ~2.3 to ~8 ka BP are inferred by the preponderance n-alkane peaks of C14-C18; westerly jet carries water vapor to this area during MIS 2 stage, and summer monsoon carries water vapor to this area during Holocene, but high aridity is not useful for vegetation flourishing; winter monsoon prevails under the dry and cold climate at desert-loess transition zone in the monsoon boundary, and aeolian activity strengthens, and vegetation flourishs under the cool and wet condition; although absolute precipitation increases under the high temperature, if the aridity increases much higher, the ecological environment will be deteriorative possibly much more.
Last Update: 2017-07-28