Testing the magnetic proxy χFD/HIRM for quantifying paleoprecipitation in modern soil profiles from Shaanxi Province, China
Testing the magnetic proxy χFD/HIRM for quantifying paleoprecipitation in modern soil profiles from Shaanxi Province, China
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DOI：
10.1016/j.gloplacha.2013.04.013
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发表时间：
2013-11-01
影响因子：
3.9
通讯作者：
Hu, Pengxiang
中科院分区：
文献类型：
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作者：
Liu, Zhifeng;Liu, Qingsong;Hu, Pengxiang
土壤是古气候的天然档案，尤其是古降水。土壤环境磁学参数是古环境和古气候研究的重要内容。通常，磁铁矿、磁赤铁矿、赤铁矿和针铁矿是控制土壤磁性的主要矿物。然而，由于母体材料的潜在影响，磁法在大面积上的应用受到限制。在此，对中国陕西省沿沿着南北样带的现代土壤剖面进行了磁性测量，以检验一种新的磁性代用指标，即绝对频率相关磁化率与硬等温剩磁磁化强度之比（chi（FD）/HHH 2），用于古降水量的估算。更具体地说，chi（FD）和HHH 2分别被用作亚铁磁体（磁铁矿和磁赤铁矿）和赤铁矿浓度的半定量代理。根据chi（FD）和Hsq散点图估计的替代chi（FD）/Hsq范围在4.5和97.6 x 10（-5）mA（-1）之间，并随着平均年降水量（MAP）从300到1000 mm系统地增加（chi（FD）/Hsq = 0.124 x MAP - 31.5，R-2 = 0.92），误差为+/- 70毫米的古降水估计，但不太相关的平均年温度（MAT）（R-2 = 0.29的MAT范围为8-15摄氏度）。对于MAP < 1000 mm，成壤亚铁磁体和赤铁矿产量都随着MAP的增加而增加，这表明这些矿物可能在遗传上相关。然而，亚铁磁体的浓度比赤铁矿的浓度增加得更明显。对于位于MAP > 1000 mm的土壤剖面，chi（FD）/Hm 2值仅为17.8 x 10（-5）mA（-1），这可能是还原溶解或蚀变的结果，亚铁磁体的影响比赤铁矿更明显。总之，这个新的古气候转换函数有潜力预测MAP < 1000 mm的全新世土壤的MAP，只要没有还原溶解或改变的铁氧化物和其他影响因素（如温度）的影响被考虑在内。(C)，2013 Elsevier B. V.保留所有权利。
Soils are natural archives of paleoclimates, especially for paleoprecipitation. Environmental magnetic parameters of soils are of great interest for paleoenvironmental and paleoclimatic investigations. Generally, magnetite, maghemite, hematite, and goethite are the main minerals controlling the magnetic properties of soils. The application of magnetic methods in large areas is, however, limited due to the potential effects of parent material. Here, magnetic measurements were conducted on modern soil profiles along a North-South transect in Shaanxi Province, China, to test a new magnetic proxy, defined as the ratio between the absolute frequency dependent susceptibility and the hard isothermal remanence magnetization (chi(FD)/HIRM) for paleoprecipitation estimation. More specifically, chi(FD) and HIRM were used as semi-quantitative proxies for the ferrimagnets (magnetite and maghemite) and hematite concentrations, respectively. The proxy chi(FD)/HIRM, estimated from the scatter plots of chi(FD) and HIRM ranges between 4.5 and 97.6 x 10(-5) mA(-1) and systematically increases with the mean annual precipitation (MAP) from 300 to 1000 mm (chi(FD)/HIRM = 0.124 x MAP - 31.5, R-2 = 0.92) with an error of +/- 70 mm for the paleoprecipitation estimation, but is less related to mean annual temperature (MAT) (R-2 = 0.29 for a MAT range of 8-15 degrees C). For MAP < 1000 mm, both pedogenic ferrimagnet and hematite production increases with increasing MAP, which suggests that these minerals are likely to be genetically related. Nevertheless, the concentration of ferrimagnets increased more markedly than that of hematite. For a soil profile located in an area where MAP > 1000 mm, the chi(FD)/HIRM value was only 17.8 x 10(-5) mA(-1) as the likely result of reductive dissolution or alteration, the effect being more marked for ferrimagnets than for hematite. In summary, this new paleoclimatic transfer function has potential to predict MAP for Holocene soils with MAP < 1000 mm, providing that there is no reductive dissolution or alteration of the iron oxides and the effect of other influential factors (e.g. temperature) is taken into account. (C), 2013 Elsevier B.V. All rights reserved.