The Sediment Susceptibility And Pollen Analysis Respond To Environmental Changes In Yin Ruins Area

In order to further understand the background of the origin, flourish and decline of Yin Dynasty, three freely disturbed natural soil profiles (Chadianpo, Guang1 and Guang2) have been derived near the site of Yin Ruins. And analyses on lithology, magnetic susceptibility and pollen of the three soil profiles in the area of Yin Ruins have been also accomplished.The analysis of lithology reveals that the three soil profiles are similar and can be divided into three parts. All consist of grey-black paleo-soil layers formed before Yin Dynasty in the bottom, different-color sub-clay layers formed after Yin Dynasty in the middle parts, and cultivable soil in the upper parts.The analysis on magnetic susceptibility represents the characters of the three parts of each profile. The upper parts of the profiles are cultivable soil. Considering the influence of human's activities, we will not discuss these parts. The middle parts are sandy clay formed by alluvial sediment. In these parts, the magnetic susceptibility is obviously higher than the other parts, and fluctuates seriously. It is may be the result of the changes of contents and the arrange of magnetism mineral caused by the origin sediment;The lower parts are gray-black paleo-soil,and the magnetic susceptibility of this parts is lower than the other parts and sharply fluctuate, which is different from the present studies of magnetic susceptibility in loess regions, but the reason is uncertain now. The magnetic susceptibility of the three soil profiles changes seriously in whole, and it becomes lower with the depth increasing, it may be by the effects of embedment.Pollen assemblage of gray-black paleo-soil in Chadianpo profile was dominated by arboreal pollen, such as Pinus, Juglans, Betula and so on,which mostly accounted for more than 60% of the total sum. The herbs pollen which was dominated by Artemisia, Compositae and Gramineae was much lower, no more than 30% in general. It represents that the paleo-vegetation in the vicinity of Anyang city was warm deciduous broad-leaved forest. The pollen assemblages of Guang1 and Guang2 in Guangrunpo which is about 20km away to the southeast of Anyang city, were similar and both dominated by herbs pollen of mesophytes and hygrophytes, such as Typha, Cyperaceae and Ranunculaceae, revealing that the paleo-vegetations were mainly marsh and grassland, which was different from the vicinity of Anyang city at that time. Although the profiles of Guang1 and Guang2 are near to each other (only1.6km apart), there were little differences between the pollen assemblages of the two profiles. There were much more mesophyte and hygrophyte herb pollen types like Cyperaceae and Ranunculaceae in Guang2 profile, which represents that it was little lower in elevation and much wetter than the location of Guang1. In the upper parts of the gray-black paleo-soil, there were increasing contents of Gramineae and Selaginella sinensis pollen, which reveals that ancient humans have already dwelled here at that time, and the forests in the vicinity have been destroyed by human activities. Above the gray-black paleo-soil in Chadianpo profile, the arboreal pollen diminished sharply, it was just at the flourishing time of Yin culture, so it might reveal the serious deforestation by ancient citizen for the construction of the city and daily life. And the similar phenomenon also could be found in the two profiles of Guangrunpo, the contents of arboreal pollen also decreased sharply at the boundary between the gray-black paleo-soil and the upper parts. The later diminished of arboreal pollen and increased of Selaginella sinensis from the three profiles revealed the process of the deforestation in Anyang and western mountain areas.