澧阳平原杉龙岗遗址埋藏古水稻土磁性矿物特性

为探明埋藏古水稻土磁性矿物特征,采用环境磁学方法研究了澧阳平原杉龙岗遗址埋藏古水稻土的磁性矿物含量、组成和粒度。结果表明,埋藏古水稻土的磁化率平均值为6.2×10~(–8) m~3/kg,饱和等温剩磁平均值为16 338×10~(–5)Am~2/kg,软剩磁平均值为773×10~(–5)Am~2/kg,退磁参数S300平均值为72%。埋藏古水稻土亚铁磁性和不完全反铁磁性矿物含量随土层深度增加不断降低,其含量均低于现代耕作水稻土层;埋藏古水稻土磁化率主要来源于亚铁磁性矿物和不完全反铁磁性矿物,且亚铁磁性矿物占相对主导地位;相对于现代耕作水稻土层,埋藏古水稻土层中磁性矿物以较粗的磁铁矿颗粒为主。

Magnetic Mineral Characteristics of Buried Ancient Paddy Soil in Shanlonggang Site of Liyang Plain

Environmental magnetism method was applied in this study to discuss the content, composition and granularity of the magnetic minerals of the buried ancient paddy soil in Shanlonggang Site in Liyang Plain in order to disclose the characteristics of magnetic minerals. The results showed that the average MS, SIRM, 'soft' IRM, S300 ratios were 6.2×10-8m3/kg, 16338.3×10-5 Am2/kg, 773.35×10-5Am2/kg and 71.99%, respectively. It also showed that the frequency dependent susceptibilityχlf was over 10%. Furthermore, the magnetic susceptibility was mainly derived from ferrimagnetic mineral and the imperfect antiferromagnetic mineral, especially from ferrimagnetic mineral. Meanwhile, the contents of ferrimagnetic and the imperfect antiferromagnetic minerals decreased with the depth, and were lower than those of current paddy soils. Finally, the results of SIRM/χlfand magnetic susceptibility, which could be used as an indicator of the magnetic grain size, indicated that the sizes of magnetic particles of the buried ancient paddy soil may be larger than those of current paddy soils.