A High Resolution Climate Record Of Moon Lake In The Middle Part Of Daxing'an Mountan Range In Northeast China During The Last 21ka: From The Evidence Of TOC, TN And δ¹³C_org

The study on rapid changes of climate events of millennium and century scale has become the hotspot in ancient climate research field. Now, there are still some problems remained to be solved in the study of the evolution of the East Asian monsoon since the the last deglaciation. Among many of paleoclimate records, lake sediment on the mainland is one of the most promising objects in the study on high-resolution paleoclimatic change since the last deglaciation. Therefore, we selected Moon Lake which is located in the middle part of Daxing'an mountan range as research subjects.According to total organic carbon (TOC), total nitrogen (TN) content, total organic carbon isotopic composition (δ¹³C_org) of the lake sediment, we reconstruct the high-resolution paleoclimate evolution of the area since 21kaB.P. .We reconstruct the evolutionary history of the ancient climate and environment since 21cal.kaB.P. . The results are as follows:during he late glacial (21-14cal.kaB.P.), TOC and TN contents is in the lowest value. The atomic ratios of TOC / TN are below 14, indicating that the contribution of terrestrial plants is very small, and organic matter in sediments is mainly from the aquatic plants. The climate of this period is relatively dry and cold, with very little terrestrial vegetation around the lake. During the last deglaciation (14-10.8cal.kaB.P.), TOC and TN contents increased rapidly, and changing rapidly in the century-scale. It can be further divided into three cold-dry events and two warm-wet events. The last cooling event is the most intense. During the last deglaciation, TOC / TN ratios were significantly increased, and most of them is higher than 14, suggesting that most of the organic matter is from the land plants of the catchment basin. During the last deglaciation,δ¹³C_org changes the most obviously and negatively in the Moon Lake and the degree of negative increase gradually. It may indicate that the coverage was poor around the lake during this period, resulting the influx of numerous terrestrial organic matter. During the Holocene (after 10.8cal.kaB.P. ),TOC and TN contents increased rapidly. During the 2-5cal.kaB.P, and this stage is the Holocene Optimum. TOC and TN content was the highest value in the whole section, suggesting that organic matter content increased in sediments, and terrestrial vegetation lush. During the Holocene,δ13Corg did not change significantly, and this may reflect that changes in terrestrial vegetation is not obvious around the lake.Contrasting the ancient climate records of the Moon Lake with other high-resolution paleoclimatic records, we found that the begining of the last deglaciation was later in the Moon Lake area than in other records, including the Greenland ice core. One possible reason is that the ancient climate changing in Moon Lake region are not synchronized with the climate changing in Greenland ice core and the other regions of East Asia. Another possible reason is that the time mode (depth - age) are differences, the time scale of Moon Lake sediment records are younger, so it is difficult to compare the ages of climate events with other ancient climate records during the last deglaciation.