共和盆地马四剖面12 cal ka BP以来的成壤环境演变

Holocene Environmental Change of Pedogenesis in the MS Profile of Gonghe Basin, China

在分析常量元素氧化物含量及其比值的基础上,结合14C测年,对共和盆地马四剖面风成沉积序列进行研究,重建了12 cal ka BP以来共和盆地成壤环境演变过程。结果表明:(1)剖面常量元素氧化物以SiO2、Al2O3为主,元素含量SiO2>Al2O3>Fe2O3>MgO>CaO>Na2O>K2O;(2)12 cal ka BP以来区域成壤环境大致经历了凉干-温润-冷干-凉润-凉干-温湿-凉干7个阶段,即11.98 cal ka BP以前区域气候凉干,风沙活动频繁,成壤作用较弱;11.98~9.75 cal ka BP气候温润,但波动频繁,成壤环境不稳定;9.75~8.09 cal ka BP气候冷干,风沙活动强,成壤作用最弱;8.09~4.78 cal ka BP气候适宜,成壤作用强;4.78~2.90 cal ka BP气候凉干,成壤环境较弱;2.90~0.67 cal ka BP气候转暖期,气候温湿,成壤作用达到最强;0.67 cal ka BP至今气候凉干,成壤作用较弱。

The paper based on the environmental characteristics revealed by concent-ration of constant element oxides and ratio, and combined with 14C dating, researching the aeolian sedimentary sequence of desertified land in the MS profile of Gonghe Basin, and rebuilt the sedimentary environmental evolution process of Gonghe since 1.2×104 cal BP. The research result shows that SiO2、Al2O3 is the main element oxide in the profile, and the order of element content is SiO2>Al2O3>Fe2O3>MgO>CaO>Na2O>K2O. The ration of the constant element oxides indicated that the climate of the Gonghe Basin had changed in temperature cycle from cool-dry-warm-humid-cool-dry-cool-humid-warm-cool-warm-moisture-cool-dry since 1.2×104 cal BP. Based on the environmental characteristics revealed by concent-ration of constant element oxides and ratio sand combined with 14C dating, the environmental evolution in the MS profile since 1.2×104 cal BP can be divided into seven stages. Before 1.198×104 cal BP, the climate has become cool-dry with strong winds prompted intense aeolian activities so the Gonghe Basin had experienced a strong sandstorm activity period with weak pedogenesis;The climate trended to be warm with frequently climatic fluctuations and the pedogenesis instability in 11.98×103-9.75×103 cal BP;From 9.75×103 cal BP to 8.09×103 cal BP, cool and dry, the activity of sandstorm was strong and the role of forming soil was the weakest;During 8.09×103-4.78×103 cal BP, the climate was suitable and the pedogenesis was stronger;From 4.78×103 cal BP to 2.90×103 cal BP, cool and dry, the role of forming soil was weak;The climate was warm and wet, and the pedogenesis was the strongest and accompanying with prominently developed paleosol in 2.90×103-0.67×103 cal BP;The climate of 6.7×10 cal ka BP was cold and dry, and the role of forming soil was poor.