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.