中文摘要：

通过对浙江金衢盆地界首红土剖面的研究,探讨其磁性特征垂向变化、影响因素及其古环境意义.结果表明,界首红土剖面粒度组成以粉砂（4～63μm）和粘土（＜4μm）为优势组分,砂含量极少,“风尘基本粒组”（10～50μm）含量较高,平均值为34％,呈现出一定的风成特性.粒度频率分布曲线显示,剖面上部（0～ 430cm）与剖面下部（430～920cm）具有相似的特性,但剖面下部更为复杂,混杂有粗粒级组分.粒度与磁性特征的相关分析表明,亚铁磁性矿物与粉砂粒级组有密切关系,而不完整反铁磁性矿物多赋存于细粒级的粘土组分中,并具有附着于石英颗粒表面的特征.界首剖面下部地层中尽管存在近源搬运或水成成因的粗粒级组分,但因其含量极少,对磁性特征的贡献往往被含量较多的细粒级组分所掩盖.该剖面磁性矿物组合自底部向上由不完整反铁磁性矿物主导向亚铁磁性矿物主导变化,这一变化特征与九江九庐（JL）风积成因红土剖面具有极大的相似性,反映了气候变化通过影响红土风化成土形成的磁性矿物组合,控制了南方红土磁性特征的变化.总体上,界首红土剖面的磁性特征自下而上的变化指示了中国南方自中更新世以来气候由湿热向冷干演变的趋势.

英文摘要：

Based on particle size and magnetic measurements of the red clay profile from Jieshou （29°02′94＂N, 119°27′15＂E）, Jinhua-Quzhou basin, this paper is aimed to investigate the vertical variations of magnetic characteristics, its influencing factors and paleoenvironmental implications. The profile is 920cm in thickness, which comprises vermiculated red clay （920-260cm） , in which a amount of not completely weathering gravel is contained between 920-740cm, uniform red clay （260 ～ 90cm） and top soil （90-0cm）. Samples were collected at 5cm intervals above the depth of 230cm, and 10cm intervals below that depth. A total of 115 samples were obtained from the profile. Particle-size analysis shows that silt （4～63μm） is the dominant fraction, ranging from 41% -68% with a mean of 61%. On the whole, clay and sand fractions decline upward, while silt fraction shows the opposite trend. The grain-size frequency curves show typical aeolian characteristics throughout the whole profile. However, the grain-size distributions of the lower part （920 ～430cm） have an additional coarser fraction in the range of 1 6 to 3 dp, suggesting a proximal source or alluvial fraction. The 10-50μm fraction, so-called ＂basic dust fraction＂, accounts for 34% on average. Correlation analysis between magnetic parameters and particle size suggests that ferrimagnetic minerals are mainly associated with silt fraction, while antiferromagnetic minerals with clay and sand fraction. The below 430cm of Jieshou profile have a coarse fraction, but because of the small percentage of sand fraction, contribution of sand fraction to the bulk magnetic properties is small in comparison to the fine-grained silt and clay fractions. Below 430cm, magnetic susceptibility （Z）, frequency-dependent susceptibility （Zfd）, susceptibility of Anhysteretic Remanent Magnetization （ZSRM）, and demagnetization parameters S_r,tio are low with minor variations. In contrast, Saturation Isothermal Remanent Magnetization （SIRM） an