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利用埃及北部Faiyum盆地获得的高取芯率沉积物岩芯,进行沉积物多种磁性参数的测量,结合有机碳、介形虫、粒度等分析,在AMS14C加速器测年的基础上,建立全新世以来湖泊沉积物磁性特征变化的时间序列.结果表明,粒度效应以及沉积后的各种次生作用对沉积物的磁性特征没有明显的影响,磁性变化主要反映了沉积物不同来源组成的相对变化.全新世前沉积物磁性较弱,主要含不完全反铁磁性矿物,与周边沙漠的物质相似,结合其粒度特征,沉积物来源应以近源物质为主.全新世早中期(约10 5.4 ka BP)沉积物磁性变化相对稳定,有机质含量也较高,指示了来自尼罗河较为稳定的物质供应;而大约5.4 ka BP尤其最近约4.2 ka BP以来,磁性的明显变化反映了流域降水减少情况下,来自青尼河物质贡献的相对增加;最近约2.0 ka BP以来沉积物的磁性变化,则更多地与盆地人类活动的强化有关.总体而言,Faiyum盆地全新世以来的环境演变主要受控于全新世以来尼罗河与盆地的水力学联系.即:全新世前盆地未与尼罗河连通时,沉积物主要来源于周边沙漠的风成物质;而受全新世早-中期来流域季风降水增加的影响,泛滥的尼罗河为盆地提供了相对稳定的物质供应,湖泊也处于高湖面;全新世晚期以来,随着流域干旱化的加剧,尼罗河与盆地的连通性开始减弱,来自高磁性的青尼罗河物质贡献开始相对增加.最近约2.0 ka BP以来,虽然仍有人工运河连接尼罗河与盆地,但沉积物磁性的显著变化更多地反映了盆地人类活动的不断强化.
Based on the dating of AMS14C accelerators and the dating of the Holocene, based on the dating of sediment cores with high coring rates obtained from the Faiyum basin in the north of Egypt, various magnetic parameters of sediments were measured. Combined with organic carbon, ostracods and particle size analysis, The results show that the grain size effect and various secondary effects after sedimentation have no significant effect on the magnetic characteristics of the sediments, and the magnetic changes mainly reflect the relative changes of sediment source composition. The former sediments were weakly magnetic and mainly consisted of incompletely antiferromagnetic minerals, which were similar to those in the surrounding desert. According to their grain size characteristics, the source of sediments should be near-sourced materials. Early and middle Holocene (about 10 5.4 ka BP) Relatively stable magnetic changes and high organic matter contents of the sediments indicate a relatively stable supply of material from the Nile. Since about 5.4 ka BP, and especially recently about 4.2 ka BP, significant changes in magnetic properties reflect the decrease in precipitation from the green The relative contribution of the Niño material contribution; the magnetic change of sediments since the recent 2.0 ka BP is more related to the enhancement of human activity in the basin Overall, the environmental evolution since the Holocene in the Faiyum basin was mainly controlled by the hydraulic connection between the Nile and the basin since the Holocene, ie, when the basin was not connected with the Nile during the Holocene, the sediment mainly came from the aeolian desert However, due to the increase of monsoon precipitation in the basin in the early-mid-Holocene, the Nile flooding provided a relatively stable material supply to the basin and the lake was also on a high lake. Since late Holocene, with the aggravation of the basin’s aridification, the Nile The connectivity with the basin began to decrease, and the material contribution from the high-magnetic Blue Nile began to increase relatively. Since about 2.0 ka BP, although there are still man-made canals connecting the Nile and basins, the significant changes in sediment magnetism more reflect the basin- Human activities continue to strengthen.