【摘要】 在滦河上游,全新世时期曾有过气候相对湿润阶段,具体表现是:就地起沙的风沙层内,形成了2层特殊的古土壤———黑沙土。黑沙土层分布的厚度不均匀,但具有明显的有机质半固结现象。2层黑沙土之间为黄色风沙层,上层黑沙土又为晚近风沙层覆盖。在下层黑沙土中散布着一些古文化遗存,石片、石核、石斧等石器主要见于下部,陶片数量则以近顶部居多。对黑沙土中的有机质进行14C测年,结果表明,下层黑沙土形成于约7990±150~3200±125aB·P·(cal·)之间,上层黑沙土形成于约3055±170aB·P·(cal·)以后。由这个遗址附近的环境分析证明,古代人类在此活动时期,当地气候处于相对湿润阶段,风沙活动虽依然存在,但可以断定黑沙土的成壤速度大于风沙物质堆积速度,使这里的先民能够依靠农耕、渔猎而生存。大约3200±125aB·P·(cal·)后,风沙堆积速度骤然加快,使黑沙土成土过程一度完全停止,在大约100多年的时间里,风沙活动强烈,形成黑沙土层之间的黄色风沙层堆积。这一时期恶劣的环境使得当时当地的先民无法生存,被迫迁移,从此出现新石器遗址的缺失。该遗址所在的丰宁地区,是影响北京沙尘暴的上源地区之一。因此,该地区环境考古学问题的研究,对了解北京地区沙尘暴变化历史有直接佐证的价值。更多还原

【Abstract】 Climate change has had obvious influences on human activity especially during ancient time. In semiarid areas of North China, the Holocene climate change is featured by humidity fluctuation. During the Holocene climate change in the upper reaches of Luanhe River surrounding Fengning, Hebei Province, there were once relatively humid periods. The humid periods are identified by two layers of paleosol——a kind of black sandy soil. The paleosol is developed on aeolian sand beds and partly cemented by organic matter, which indicates the presence of a warm and humid climate with relatively abundant vegetation. The thickness of the soil layers is quite variable. In between two of the soil layers, there is a yellow aeolian sand bed, while the upper soil layer is covered by recent drifting sand. The radiocarbon dating results of the organic matter of the paleosol samples from a section near Senjitu, Fengning County, shows that the lower paleosol was formed between 7 990±150aB.P.(cal.) and 3 200±125 aB.P.(cal.), which was consistent with the Holocene Megathermal (8 000～3 000aB.P.) in China. The upper soil layer was formed after 3 055±170aB.P.(cal.) where as the aeolian sand beds in between the two soil layers was formed during 3 200±125aB.P.(cal.)~ 3 055±170aB.P.(cal.) under an arid climate with a strong aeolian process. Therefore, it is a record of an arid climate event, which interrupted the soil formation process. This event can be correlated to concurrent events with different forms identified in a vast area of North China. It is one of the symbols of the end of the Megathermal and has implications to the global change. In the lower paleosol, there are some ancient cultural relics. A number of fine stone tools, including stone flakes, choppers, and axes, were found mainly from the bottom upwards and many pottery pieces were found near the top of the profile. The Neolithic relics show that it was a location of human activities during the Holocene Megathermal. Analysis of the surroundings of the relic site indicates that the climate was humid enough to support the ancient people of that time. Although some bodies of drifting sand may have existed at that time, the rate of soil formation exceeded the rate of drifting sand accumulation. Thus, the ancient people could subsist or perhaps thrive on food acquired by farming, hunting, and possibly fishing. At sometime after 3 200±125aB.P.(cal.), drifting sand accumulation probably accelerated due to the increased aridity. Soil formation ceased and thick sand layers were deposited on top of the palaeosol. The deterioration of climatic conditions probably forced the ancient community to move out of the area. This would account for the lack of younger Neolithic sites of permanent human habitation around Fengning. The cultural relics at the top of the lower paleosol correspond to the lower Xiajiadian culture. The climate event, which interrupted the soil formation and cultural development, might be the caused for the change from an agricultural culture of lower Xiajiadian to a nomadic culture of upper Xiajiadian. Fengning is currently one of the sources of the large dust storms, which often affect Beijing. The environmental archeological studies of Fengning region can offer direct evidence for determining and understanding the dust storm history of Beijing.更多还原