Heinrich-5Event revealed by high-resolution grain-size and magnetic susceptibility records and its significance of climate evolution in the last glacial at Hongtong,Shanxi,China
The millennial-scale fluctuations of Heinrich events during the last glacial stage initiated from the North Atlantic have been widely discovered in East Asia.However,which event has the most remarkable impact on East Asia or even the Northern Hemisphere remains unclear.There are widely distributed loess deposits,the best climate proxies,in the Linfen Basin,Shanxi province.In this study,we collected OSL dating samples and powder samples at a 0.5 cm intervals to analyze grain size and magnetic susceptibility for a 10.5 m thick loess sequence at Dongyugou of Hongtong,Shanxi.Dating results show that the section is in an age range from67.7~13.0 ka.Grain size and susceptibility data suggest an obvious H_5climate event of the last glacial at the depth of 47.3 ka.Therefore,this cores could be divided into two parts.In the early time(67.7 ~47.3 ka),the content of coarse silt(20~63mum)and sand fraction(>63mum)was overall low,but magnetic susceptibility was relatively high.On the contrary,in the later time(47.3~13.0 ka),the content of coarse silt and sand fractions increases, while magnetic susceptibility is low.This implies that Asian winter monsoon was weak and summer monsoon was strong in the early time,while in the later period,Asian winter monsoon substantially enhanced and summer monsoon significantly weakened.The evolution models of last glacial climate demarcated by H_5(~47.0 ka)are comparable in East Asia,Eastern Mediterranean and even North America.It is supposed that ice accumulation in the Arctic in this period led to climate changed colder in East Asia and the Northern Hemisphere.This cognition plays an important role in deep understanding of the evolution trend of MIS3 climate in East Asia.