[M-IS16] Paleoclimatology and paleoceanography

[MIS16-P16] Paleovegetation changes in the northern Mongolia since the last glacial

*Ryosuke Imaoka¹, Koji Shichi², Hitoshi Hasegawa¹, Niiden Ichinnorov³, Nagayoshi Katsuta⁴, Davaasuren Davaadorj⁵, Masafumi MURAYAMA¹, Masao Iwai¹, masami izuho⁶ (1.Kochi University, 2.Forestry and Forest Products Research Institute, 3.Paleontological Center of Mongolia, 4.Gifu University, 5.National University of Mongolia, 6.Tokyo Metropolitan University)

Keywords:Pollen analysis, Vegetation reconstruction, Last glacial period, Permanent frost, Global warming

Northern Mongolia is located at the boundary between northern permafrost and southern desert belts and is sensitive to climate change such as permafrost thawing. In this study, we aimed to reconstruct changes in paleoenvironment and paleovegetation in northern Mongolia since the last glacial based on the analysis for lake sediment record of Sangiin Dalai lake. We took lake bottom sediment by gravity core in August 2016 (16SD02; 84 cm length), and five boring cores in March 2019 (19SD01~05; ca. 13 m length). Using these sediment cores, we performed palynological analysis at Forestry and Forest Products Research Institute and elemental composition analysis using XRF core scanner at Center for Advanced Marine Core Research, Kochi University.
Based on palynological analysis and biome reconstruction (Tarasov et al., 2000), paleovegetation changes from steppe-desert biome dominated by Artemisia and Chenopodiaceae in the last glacial to steppe-taiga biome composed of mixture of Artemisia and Pinus in the Holocene were reconstructed. Elemental composition analysis reveals that higher Si/Ti ratio in sand layer and higher Mn/Fe ratio (oxic environment) and Ca/Ti ratio (saline lake) in silt layer during the last glacial, and low Ca/Ti ratio (less saline lake) during the Holocene. Thus, marked paleoenvironmental change from shallow lake and alluvial plain during the last glacial to high lake-level during the Holocene are reconstructed. These result, in conjunction with palynological data-sets in surrounding area (Kotokel lake in southern Siberia: Shichi et al., 2009; and Orog lake in southern Mongolia: Yu et al., 2019) suggests that predominance of steppe-desert vegetation in southern Siberia and northern/southern Mongolia during the last glacial, and turned to Forest vegetation in southern Siberia, steppe-taiga vegetation in northern Mongolia, and desert vegetation in southern Mongolia during the Holocene, which likely caused by permafrost thawing by insolation change and climatic warming in deglaciation period.



References

Shichi, K., et al. (2009). Late Pleistocene and Holocene vegetation and climate records from Lake Kotokel, central Baikal region. Quaternary International, 205, 98-110.

Tarasov, P. E., et al. (2000). Last glacial maximum biomes reconstructed from pollen and plant macrofossil data from northern Eurasia. Journal of Biogeography, 27, 609-620.

Yu, K., et al. (2019). Late Quaternary environments in the Gobi Desert of Mongolia: Vegetation, hydrological, and palaeoclimate evolution. Palaeogeography, Palaeoclimatology, Palaeoecology, 514, 77-91.