Quaternary strata lithological characteristics and environmental geological significance of borehole WKZK01 in the eastern Songnen Plain
[Objective]Study of the Quaternary stratigraphical characteristics of the eastern Songnen Plain is of particular importance for gaining an understanding of regional climate change and the evolution of sedimentary environments.To data,however,there has been comparatively little research focusing on the Quaternary strata in this area,which has accordingly limited our comprehension of the mechanisms underlying changes in the regional climate and environment.[Methods]In this study we focused on the borehole WKZK01 in the eastern Songnen Plain.On the basis of lithological characteristic analysis,we obtained dating,sedimentary environment evolution,and climatic evolution information using optically stimulated luminescence,palynology,and laser grain size analytical methods,and based on comparisons with the results obtained from a typical Huangshan section,Harbin,we discuss the Quaternary stratigraphy of the borehole and the sedimentary environments it reflects.[Results]The Quaternary strata in Wangkui county are divided from old to new as follows:the middle Pleistocene Huangshan Formation,the middle Pleistocene Harbin Formation,and the upper Pleistocene Guxiangtun Formation,with an absence of a Holocene Tantu Formation.The Huangshan Formation is 13.05 m thick,with a median grain size(Md)ranging from 7.77 μm to 11.84 μm,and an average value of 9.62 μm.Pollen zone I-1 is dominated by xerophytic herbaceous pollen,with small amounts of mixed coniferous and broadleaf woody plant pollen,although lacks pollen derived from hydrophilic herbaceous plant.The Harbin Formation is 24.05 m thick,with a median grain size(Md)ranging from 9.67 μm to 14.98 μm,and an average value of 11.74 μm.Pollen zone I-2 is still dominated by xerophytic herbaceous pollen,with that derived from mixed coniferous and broadleaf woody plants as the secondary component,and the appearance of hydrophilic herbaceous plant pollen.The Guxiangtun Formation is 15.6 m thick,with a median grain size(Md)ranging from 11.61 μm to 19.91 μm,and an average value of 14.12 μm.Compared with the earlier stages,pollen zone II has a less abundant pollen content,although is characterized by an increase in hydrophilic herbaceous pollen,and a marked decline in the content of pollen derived from xerophytic woody and herbaceous plants.[Conclusion]The Huangshan Formation represents lacustrine deposits,with pollen zone I-1 providing evidence of a cool and dry climate during the early Middle Pleistocene.The Harbin Formation also comprises lacustrine deposits,with the pollen record in zone I-2 indicating a cool and humid climate during the late Middle Pleistocene.The Guxiangtun Formation comprises fluvial deposits,with pollen zone II recording a cold and wet climate during the Late Pleistocene.[Significance]The borehole WKZK01 provides a record of the environmental evolution of a small lake adjacent to the large Songnen paleolake,revealing a transition from the lake center to the margin and eventually disappearing with the formation of rivers.
万方数据
维普
