基于河北省白洋淀地区老河头剖面沉积物的粒度组成与磁化率特征,结合6个AMS~(14)C测年结果,重建了该地区25. 5 cal ka BP以来的气候环境变化历史。结果显示,25. 5 cal ka BP以来可以划分为7个较大的气候阶段:25. 5~ 20. 9 cal ka BP(610~ 515 cm),沉积环境以微弱的流水沉积和风力沉积为主;20. 9~ 10. 7 cal ka BP(515~ 388 cm),该区河流作用减弱,风力堆积加强;10. 7~ 8. 6 cal ka BP(388~ 335 cm),该区降水增加,白洋淀湖泊面积扩大,水位升高;8. 6~ 7. 2 cal ka BP(335~ 299 cm),风力作用加强,以风力堆积为主;7. 2~ 3. 2 cal ka BP(299~ 200 cm),沉积环境以稳定的湖相沉积为主,后期流水作用增强;3. 2~ 1. 3 cal ka BP(200~ 110 cm),该区流水作用显著,有泛滥性的洪水在此期间出现;1. 3 cal ka BP至今(110~ 0 cm)降水减少,但流水作用仍然明显。
英文摘要:
Laohetou profile is located in the west of Baiyangdian depression. A 610 centimeter-deep sediment profile was studied in this paper. The AMS ~(14)C measured data revealed that the sediment profile deposited since 25. 5 cal ka BP. Combined with chronological data,grain size characteristics,susceptibility and sedimentary characteristics,the evolutionary process and environment features during the past 25. 5cal ka BP were reconstructed. Results showed that there were seven stages as following. 25. 5 - 20. 9 cal ka BP(610 - 515 cm) is a fluvial facies and wind accumulation period;in 20. 9 - 10. 7 cal ka BP (515 - 388 cm),fluvial action is weakened,and wind accumulation may be strengthened;in 10. 7 - 8. 6 cal ka BP (388 - 335 cm),precipitation increases and water accumulates,lakes expanding during this stage;8. 6 - 7. 2 cal ka BP (335 - 299 cm) is a wind accumulation period;7. 2 - 3. 2 cal ka BP(299 - 200 cm) is a lacustrine facies period;3. 2 - 1. 3 cal ka BP(200 - 110 cm) is a fluvial facies period;from 1. 3 cal ka BP to now(110 - 0 cm),the precipitation decreases,but fluvial function is still obvious.