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通过对安徽宣城向阳剖面Munsell指标、风化强度、磁学参数、稳定碳同位素等的研究,提出几点与前期研究者的不同看法:(1)向阳剖面色调曲线与游离态铁(Fed)、铁游离度(Fed/Fet)、风化淋溶系数(BA)曲线表明,顶部黄棕色土的风化程度偏低,中、下部的风化程度普遍高于上部.除了顶部黄棕色土层,其余各层红色调深浅的变化,与风化强度无必然的联系.色调的变化可能是次生氧化铁矿物赤铁矿和针铁矿相对含量变化的结果.因而仅以剖面内部不同层次间颜色的变化来判定存在“沉积-成土”序列,是不充分的.(2)向阳剖面无网纹或网纹发育较弱的层次磁化率(x)较高;而在网纹发育的层次,由于大量超顺磁颗粒(SP)和稳定单畴(SSD)被淋失或破坏,x低于均质红黏土近一个数量级.向阳剖面x的控制因子并不是风化成土作用的强度,因而不再有明确的古气候意义,以x曲线来证实存在多个“沉积-成土”过程旋回是不正确的.(3)向阳剖面有机质δ13C曲线说明研究地区自第四纪晚期以来,森林缩减,C4植物增加;但仍无法证实该剖面存在多个“沉积-成土”过程的旋回.(4)目前的证据尚难证实向阳剖面存在类似黄土高原“黄土-古土壤”序列的沉积旋回.
Through the study on the Munsell index, weathering intensity, magnetic parameters and stable carbon isotopes of the Xiangyang Section in Xuancheng, Anhui Province, this paper puts forward some different opinions from the previous researchers: (1) The tone curve of the Xiangyang section is similar to that of free iron, The curves of freeness (Fed / Fet) and weathering leaching coefficient (BA) indicate that the weathering of the top yellow-brown soil is low and the weathering of middle and lower parts is generally higher than that of the upper part. Except for the top yellow-brown soil, The change of shades may be the result of the change of the relative content of hematite and goethite in the secondary iron oxide mineral, so the color change only depends on the color change of the different layers in the cross section (2) There is a high level of susceptibility (x) in the sunny section with no or weakly developed streaks, while at the level of the streaks, a large number of super-smooth Magnetic particles (SP) and stable single domains (SSDs) are either leached or destroyed, and x is nearly an order of magnitude lower than homogeneous red clay. The controlling factor for the sunny section x is not the intensity of weathering and soil formation and therefore no longer clear Paleoclimatic significance, with the x curve to confirm the existence of more (3) The δ13C curve of the organic matter in the Xiangyang section shows that the forest has been reduced and the C4 plant increased since the late Quaternary in the study area. However, it still can not be confirmed that there are multiple sediments (4) At present, it is difficult to verify the existence of sedimentary cycles similar to the “loess-paleosol” sequences on the Loess Plateau in Xiangyang section.