安徽郎溪黄棕色土—红土二元结构土壤剖面的成因与长江流域第四纪晚期古气候演变

安徽宣郎广一带,黄棕色土-红土二元结构地貌十分常见。本文在郎溪选择了一个典型的黄棕色土-红土剖面,进行粒度组成和元素地球化学性状的研究,结果表明:(1)研究剖面上部黄棕色土的粒度组成和元素地球化学特征,与宣城、九江黄棕色土和镇江下蜀黄土十分一致,说明研究区域的黄棕色土确实与长江流域广泛分布的下蜀黄土同源。郎溪剖面粒度和元素地球化学特征的变化较均匀,尤其黄棕色土→埋藏红土(包括均质红土和网纹红土)间呈连续过渡,无沉积间断,表明埋藏红土的物源与黄棕色土和下蜀黄土相似,具典型的风积成因特性。(2)与黄棕色土相比,埋藏红土粒径偏细,风化成土作用显著增强。从埋藏红土逐渐过渡到黄棕色土,反映的可能是长江流域晚更新世初期,末次间冰期结束、末次冰期开始时的一次重大的古气候演变事件,但仍需确凿的年代学证据。

PEDOGENESIS OF YELLOW-BROWN EARTH-RED CLAY PROFILE IN LANGXI COUNTY,ANHUI PROVINCE AND PALEOCLIMATIC CHANGE IN THE YANGTZE RIVER VALLEY,SOUTHEAST CHINA IN THE LATE QUATERNARY PERIOD

Soil profiles of double-layer structure with Yellow-brown Earth (YBE) overlying Red Clay (RC) are commonly seen in the Xuancheng-Langxi-Guangde region, Anhui Province. Particle-size and geochemical characteristics of a selective YBE-RC soil profile in Langxi County, Anhui Province were studied. Results show that the YBE of the studied profile is quite coincident in particle-size composition and geochemical characteristics with that in Xuancheng and Jiujiang, and also the Xiashu Loess in Zhenjiang, Jiangsu Province, which strongly suggests that the YBE in the study areas shares the same provenance with the Xiashu Loess, widely distributed along the Yangtze Valley. The Langxi profile is vertically even in particle-size and geochemical characteristics, and also shows continuous transition between YBE and RC without any depositional interruption. This suggests that the underlying RC of the profile shares a similar origin with the YBE and the Xiashu Loess and was derived from typical aeolian-dust deposition. Compared with the YBE, however, the underlying RC is finer in particle-size and more intensively weathered. The transition from the RC to the YBE might record a great paleoclimatic change at the early stage of the Late Pleistocene, when the Last Interglacial ended and the Last Glacial began. However, more work needs to be done to find some irrefutable chronological evidence.