泥河湾盆地板井子旧石器时代遗址的形成过程

Formation processes of the Banjingzi Paleolithic site in the Nihewan Basin

板井子遗址是泥河湾盆地晚更新世早期的一处重要遗址,光释光年代为距今8~9万年。本文以2015年出土的考古材料为研究对象,从地层的沉积环境、考古材料本体的埋藏特点两个角度,对板井子遗址的形成过程进行分析。分析表明,主文化层第5层为近原地埋藏类型,水流作用对小尺寸标本的保存及标本的空间集聚特征影响较大,但石制品技术类型组合等基本的人类行为信息仍较为完整;第4、6层均为水流搬运产生的异地埋藏,蕴含的人类行为信息有所缺失。此项分析为提取、研究考古遗址所蕴含的古人类的居址选择、土地利用方式、考古材料使用废弃等方面的信息奠定了基础。

Banjingzi is an important open-air site with the age of 80-90 kaBP in the east margin of Nihewan basin in North China.Several excavations were conducted in 1984,1986,1988,1990 and 1991.In 2015,a new excavation project was organized at this site by staff from the Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences(IVPP)and Institute of Hebei Provincial Cultural Relics.A total of 36 m2 was exposed,and three archaeological layers named layer 4,layer 5 and layer 6 were recognized from the profile,with the thickness of about 0.5 m,1.6 m,0.3 m,respectively.Layer 5 yielded the most abundant archaeological remains,including 2563 stone artifacts,1028 animal bones and 716 natural pebbles(L≥50 mm),while together only about 110 pieces were recovered from other two layers.Based on materials collected in 2015 mentioned above,this paper presents a formation processes study of three archaeological layers recognized at this site by sedimentary and archaeological indicators(particularly the lithic assemblage composition,debitage size distribution,artifact conditions,orientation analysis and spatial patterning).Some important evidence and tentative conclusions could be drawn from our studies as below.Layer 5 was buried mainly in grey-yellow and grey-green silts,fine sands and clays,and several coarse sand belts and thin beds with a few pebbles encased in the deposit.Stone artifacts are basically unabraded and fresh,and display a coherent assemblage composition,with core and debitage accounting for 3.74%,89.67%respectively.Artifacts both in horizontal and vertical space show dense accumulations,however,some minor linear and circle patterns can be recognized.The proportion of flaking debris smaller than 20 mm is about 58.7%less than that of the debitage size distribution experiment data obtained by authors of this paper.In addition,the archaeological materials show relatively obvious preferred orientation and inclination.Multiple lines of evidence above suggest that layer 5 has been preserved in a near-primary context and only disturbed by some moderate hydraulic forces occasionally,which mainly results in a large amount of smaller debitage washed out from the site,and has altered the original site configurations to some extent.The assemblage integrity of this layer is still relatively high as a whole and suitable for analyzing early hominin behaviors except the spatial analysis.Layer 4 was buried in fine sands with a few pebbles,while layer 6 was covered totally in sand-gravel.From the qualitative point of view,these two layers have been buried in secondary environments where artifacts were transported by water flows from other areas nearby.