Holocene Climate Evolution:Information From The Lacustrine-Fluvial Sediment In Baiyangdian Area,North China Plain

On the basis of multiple proxy records of a BZ section in the Baiyangdian paleo-lake,including grain size,magnetic susceptibility?MS?,TOC,TN,C/N ratio,?13C,?15N,Chroma and carbonate content,combined with accelerator mass spectrometry¹⁴C data,we reconstructed the Holocene climate in the study area.The results showed that from 10.0 to 6.3 kyr BP,the study area experienced an interval of increasing precipitation and water level at Lake Baiyangdian.The extended sampling period had a short interval of around 8.4 kyr BP.The climate during this stage was relatively humid.The water level dropped abruptly,however,at 6.5 kyr BP,as a result of a weak monsoon event.Subsequently,the climate recovered to a humidity ranging from 6.3 to 2.9 kyr BP,and simultaneously,the continuous lacustrine sediment of the strata indicated that the water level of Lake Baiyangdian had expanded rapidly and reached the sampling point.After 2.9 kyr BP,the climate in the region changed again from humid to dry.The abrupt increase in MS after?1 kyr BP?993 AD?was consistent with records in local chronicles of human activities,which have indicated that the environment in the study area was influenced by human activities.Through a comparison of the archive of the BZ section and the East Asian summer monsoon?EASM?records,we found that precipitation in the study area was controlled by the EASM.A series of cold Holocene events were clearly recorded by the sediment in the BZ section,and these events were synchronous with the North Atlantic ice-rafting events?IRD?.The connection between the experimental results of the BZ section and the EASM and the IRD indicated that climate evolution in the study area was affected by a variety of EASM and IRD.