中全新世至西汉时期沁河下游环境变迁浅析

Brief Analysis on the Environmental Evolvement of the Qin River Downstream from the Middle Holocene to Western Han Dynasty

徐堡遗址是豫西北以及晋南地区十分重要的一处龙山时期(5 000—4 000aBP)城址。对沁河下游地区新石器遗址地貌分布规律、徐堡剖面粒度特征和历史时期沉积速率的研究表明:仰韶文化时期人类居住在青峰岭或者冲积平原的高黄土台地之上,仰韶文化(7 000—5 000aBP)末期或者龙山文化早期沁河下切,才使得沁河两岸的冲积平原能适合龙山时期的人类在此生产生活。西周时期至西汉时期早期,徐堡剖面沉积稳定,并且据剖面粒度特征推测,徐堡遗址当时是一高河漫滩的地貌位置。西汉末期,徐堡遗址又一次经历了较大洪水的袭扰,洪水漫延超过徐堡城内地面的高度,遗址又再次被弃。西周至西汉时期,沉积速率约为0.1cm/a,西汉时期沉积速率约为0.2cm/a,宋代时期的沉积速率约为0.1cm/a;西汉时期人口规模的扩大和经济活动的频繁以及农业技术的进步,造成黄河流域水土流失严重,徐堡剖面的沉积速率能够很好反映出当时的沉积过程以及沉积特征。

Xubao site is located in the northwest of Henan and southeast of Shanxi Province, and is an impor- tant Neolithic site of the Longshan period （5 000--4 000 aBP）. The landform distribution law in Neolithic sites of Qin River downstream areas, grain size characteristics in Xubao profiles and historical deposition rate during the study period showed that human of Yangshao culture （7 000--5 000 aBP） lived on Qingfengling hill or loess tableland on alluvial plains. During the late Yangshao or early Longshan culture （5 000- 4 000 aBP） period, the bed of Qin River was cut down and the human of Longshan culture were able to live on the alluvial plains since then. From Western Zhou Dynasty to the early Western Han Dynasty, Xubao profile indicated that the stability of deposition and particle size characteristics of section speculated that Xubao site was a high floodplain geomorphic position. In the late Western Han, Xubao site had experienced a large flood again, floods spread all over the ground of the site and Xubao was abandoned again. From Western Zhou Dy- nasty to the Western Han Dynasty, the deposition rate was about 0.1 cm/a, deposition rate was about 0.2 cm/a in Western Han Dynasty, deposition rate was about 0.1 cm/a in Song Dynasty, indicating the expan- sion of humankind activities during the Western Han Dynasty, population growth of the Western Han Dy- nasty and the frequent economic activity as well as agricultural technology progress, accelerated serious soil erosion in the Yellow River Basin. Xubao profile can well reflect the erosion process and the deposition char- acteristics in the historical period.