The evolution of Holocene climate was investigated using grain size and magnetic susceptibility of the Holocene paleosols from Baicaoyuan(BCY),Xifeng(XF) and Linyou(LY) sections in the northwest,central and southern C...The evolution of Holocene climate was investigated using grain size and magnetic susceptibility of the Holocene paleosols from Baicaoyuan(BCY),Xifeng(XF) and Linyou(LY) sections in the northwest,central and southern Chinese Loess Plateau(CLP).The results show that the Holocene in the B CY,XF and LY paleosol sections could be divided into three phases:during the early Holocene(11.8-10.5 kyr B.P.),increased magnetic susceptibility(χ) and frequency-dependent magnetic susceptibility(χ) and decreased median grain size(Md) indicate that the East Asian Summer Monsoon(EASM) has become more intense and the climate has changed from cold to warm.During the middle Holocene(10.5-5.0 kyr B.P.),the values of χ,χand 2-5 μm grain-size fraction(GT2/5) are higher and Md and 30-63 μm grain-size fraction(GT3 0/6 3) are the lowest,which reflect a warm and humid regional climate.At~8.0 kyr B.P.,there was a transient dry-cold climatic spike corresponding to a Heinrich Event,the cold event was likely due to the collapse of the Laurentide ice sheet.During the late Holocene(5.0-0 kyr B.P.),χ and χvalues are the lowest,while Md and GT30/63 are high,as proxies of a weakened EASM,when the dry-cold climate prevailed in the region.Decreased irradiance since 5.0 kyr B.P.may have caused climatic cooling and drying.Spatially,the increased main peak values and skewness from BCY,XF to LY sections show that the grain size became fine,the East Asian Winter Monsoon(EAWM) reduced,and climate was warmer and wetter from northwest to southeast.In addition,Md can be used as alternative proxy for EAWM,while χis positive with the intensity of EASM under semiarid climate conditions in CLP.展开更多
n-Fatty acids(n-FAs)are widely investigated in lake sediments,yet less attention has been given to soil sedimentary n-FAs primarily derived from terrestrial plants.In this study,we performed an analysis of n-FA distri...n-Fatty acids(n-FAs)are widely investigated in lake sediments,yet less attention has been given to soil sedimentary n-FAs primarily derived from terrestrial plants.In this study,we performed an analysis of n-FA distributions in modern plants on the Loess Plateau,China.It showed that n-FAs were generally dominated by n-C16,and that short-chain(C16-C20),medium-chain(C22-C26)and long-chain(C28-C32)n-FAs accounted for 49.7%,33.7%and 16.6%,respectively.The LTR(long-chain/total ratio),and medium-chain EOP(even/odd predominance)are likely to differentiate between dicots and monocots in modern plants.It is believed that this study will promote the paleo-application of soil sedimentary n-FAs on the Loess Plateau.展开更多
基金Under the auspices of the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(No.2019QZKK0704)Natural Science Foundation of China(No.41772168,42103046)Natural Science Foundation of Gansu Province(No.20JR5RA272,20JR5RA226)。
文摘The evolution of Holocene climate was investigated using grain size and magnetic susceptibility of the Holocene paleosols from Baicaoyuan(BCY),Xifeng(XF) and Linyou(LY) sections in the northwest,central and southern Chinese Loess Plateau(CLP).The results show that the Holocene in the B CY,XF and LY paleosol sections could be divided into three phases:during the early Holocene(11.8-10.5 kyr B.P.),increased magnetic susceptibility(χ) and frequency-dependent magnetic susceptibility(χ) and decreased median grain size(Md) indicate that the East Asian Summer Monsoon(EASM) has become more intense and the climate has changed from cold to warm.During the middle Holocene(10.5-5.0 kyr B.P.),the values of χ,χand 2-5 μm grain-size fraction(GT2/5) are higher and Md and 30-63 μm grain-size fraction(GT3 0/6 3) are the lowest,which reflect a warm and humid regional climate.At~8.0 kyr B.P.,there was a transient dry-cold climatic spike corresponding to a Heinrich Event,the cold event was likely due to the collapse of the Laurentide ice sheet.During the late Holocene(5.0-0 kyr B.P.),χ and χvalues are the lowest,while Md and GT30/63 are high,as proxies of a weakened EASM,when the dry-cold climate prevailed in the region.Decreased irradiance since 5.0 kyr B.P.may have caused climatic cooling and drying.Spatially,the increased main peak values and skewness from BCY,XF to LY sections show that the grain size became fine,the East Asian Winter Monsoon(EAWM) reduced,and climate was warmer and wetter from northwest to southeast.In addition,Md can be used as alternative proxy for EAWM,while χis positive with the intensity of EASM under semiarid climate conditions in CLP.
基金We would like to thank Dr.Z.Wang and Prof.W.G.Liu for assisting in field sampling.This work was supported by the NationalNatural Science Foundation of China(Grant No.41420104008)ChineseAcademy of Sciences(Nos.132B61KYSB20170005,QYZDY-SSw-DQC001 and ZDBS-LY-DQC033).
文摘n-Fatty acids(n-FAs)are widely investigated in lake sediments,yet less attention has been given to soil sedimentary n-FAs primarily derived from terrestrial plants.In this study,we performed an analysis of n-FA distributions in modern plants on the Loess Plateau,China.It showed that n-FAs were generally dominated by n-C16,and that short-chain(C16-C20),medium-chain(C22-C26)and long-chain(C28-C32)n-FAs accounted for 49.7%,33.7%and 16.6%,respectively.The LTR(long-chain/total ratio),and medium-chain EOP(even/odd predominance)are likely to differentiate between dicots and monocots in modern plants.It is believed that this study will promote the paleo-application of soil sedimentary n-FAs on the Loess Plateau.
