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首页> 外文期刊>Chinese science bulletin >Do multiple cycles of aeolian deposit-pedogenesis exist in the reticulate red clay sections in southern China?
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Do multiple cycles of aeolian deposit-pedogenesis exist in the reticulate red clay sections in southern China?

机译：中国南方的网状红黏土区中是否存在多个风成岩成藏循环？

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The Xiangyang reticulate red clay section was newly sampled in high-resolution. The viewpoints different from the previous studies are put forward after studying Munsell color values, weathering degrees, magnetic parameters and stable carbon isotopic compositions of the section. They are as follows: (1) The curves of hue, DCB extracted iron (Fe_d), DCB extracted iron/total iron ratio (Fed/Fe_t), weathering index (BA) of the section show that the redness is not significantly correlated with the weathering degree of the layers though the uppermost yellow-brown-colored layer is relatively weakly weathered. The variation in hues of the section is possibly attributed to the change of hematite and goethite contents. It is insufficient to determine the existence of the multiple deposit-pedogenesis cycles in the section, like the loess-paleosol sequence in Chinese Loess Plateau, only by the color variation. (2) Magnetic susceptibility (χ) values in the non-reticulate and weakly reticulate layers are high; but are quite low in the reticulate red clay layer. The former are more than ten times higher than the latter because of the leaching and collapse of superparamagnetic (SP) and stable single domain (SSD) magnetic particles during the plinthitic processes. Hence, χ values in the section are not controlled by weathering and pedogenic processes, and no longer have clear paleoclimatic implication. It is not correct to prove the existence of the multiple deposit-pedogenesis cycles in the section using χ curves. (3) The organic δ~(13)C curve of the section illustrates the reduction of forests and increasing of C4 plants in the study area since the late stage of the Quaternary period. It could not prove the existence of the multiple deposit-pedogenesis cycles in the section either. (4) As a matter of fact, it is difficult to prove the existence of the multiple deposit-pedogenesis cycles in the Xiangyang section like the loess-paleosol sequence in Chinese Loess Plateau using the evidence available currently.
机译：襄阳网状红黏土剖面是高分辨率新采样的。通过研究该断面的孟塞尔色值，风化度，磁参数和稳定的碳同位素组成，提出了与以往研究不同的观点。它们是：（1）断面的色调，DCB提取铁（Fe_d），DCB提取铁/总铁比（Fed / Fe_t），风化指数（BA）的曲线表明，红色度与该区域没有显着相关性。尽管最上层的黄棕色层的风化程度相对较弱。该部分的色调变化可能归因于赤铁矿和针铁矿含量的变化。仅通过颜色变化就无法确定该部分中是否存在多个沉积-成岩循环，如中国黄土高原的黄土古土壤序列。 （2）非网状和弱网状层的磁化率（χ）较高；但在网状的红粘土层中含量较低。前者比后者高出十倍以上，这是因为在多次软化过程中超顺磁性（SP）和稳定的单畴（SSD）磁性粒子的浸出和崩塌。因此，剖面中的χ值不受风化和成岩作用的控制，并且不再具有明确的古气候含义。用χ曲线证明截面中存在多个沉积-成岩作用周期是不正确的。 （3）该断面的有机δ〜（13）C曲线说明了自第四纪晚期以来研究区森林的减少和C4植物的增加。也不能证明该部分中存在多个沉积物-成矿作用循环。 （4）事实上，利用现有证据难以证明像中国黄土高原的黄土古土壤序列一样，襄阳地区存在多个沉积-成岩循环。

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