下川遗址水井背地点位于下川村东侧腰掌村处，地理坐标为35°26′49″N，112°01′26″E，海拔高度约为1600米，总共发掘QX2015T4、QX2015T5两个探方，两个探方地层堆积情况基本类似，两个探方堆积可划分为上下两大文化层，上文化层为距今2.6万~2.5万年旧石器晚期中段石叶-细石叶技术遗存，下文化层为距今4.4万~3.3万年旧石器晚期早段简单石核-石片技术遗存，其中以下文化层堆积更为丰富。QX2015T4探方出土石制品最主要原料为燧石，脉石英次之，偶见玛瑙、石英岩的使用，石料整体形态较为破碎，致使石制品整体尺寸偏小。下文化层出土石制品主要包括了锤击石核、石叶石核、石叶、石片以及各类工具，工具主要包括边刮器、楔形析器、锯齿刃器、尖状器、琢背小刀等器型，种类丰富。通过对下文化层石制品的整理与研究，下文化层主导技术类型为简单石核-石片文化中的小石片石器工业，剥片方式以锤击法为主，砸击法也见辅助使用，锤击石核见以台面为导向、以剥片面为导向两大剥片组织策略，其中以较为原始的台面导向剥片思路为主。下文化层出土的少量石叶技术产品观察到台面修理、核身预制等技术特征，据此推测下文化层可能存在石叶技术。本探方上文化层出现了典型的细石叶技术类型。此时锤击石核转为较进步的剥片面导向剥片思路占据主流，修理台面技术使用率提高，砸击法在剥片行为中使用率大幅下降。石器类型出现了端刮器等典型旧石器时代晚期器型，边刮器仍为最主要工具类型。上文化层出土少量石叶技术产品仍可观察到较为明确的技术特征。整体而言，从下文化层到上文化层，简单石核-石片技术长期延续，但有所发展；两个时段内均零星见有石叶技术产品；直至旧石器晚期中段成熟的细石叶技术出现并发展。

通过考察同时段中国北方地区、俄罗斯阿尔泰地区、贝加尔湖地区以及蒙古戈壁（Gobi）地区遗址，推测本探方旧石器晚期早段所见石叶技术因素应为MIS3阶段人群区域间流动携带传入，同时还带来了琢背小刀、尖状器等复合工具类型。但受气候条件影响及华北长期延续的简单石核传统下，石叶技术因素一直未能占据主流。旧石器晚期中段的石叶-细石叶技术与前段遗存至少有3000年的时间缺环，但石叶技术与细石叶技术在石核形态、两种技术在剥片思路上存在一定的相似性，暗示两类技术相关性研究的巨大潜力。

综上，从本探方出土遗存观察到简单石核-石片技术从旧石器晚期早段到中段进步特征，推测于旧石器晚期早段可能存在石叶技术因素，为重新思考华北地区旧石器晚期中段石叶-细石叶技术体系来源提供了新的思路。

Shuijingbei Locality (112°01′26"E, 35°26′49"N) of Xiachuan Site is located in the Yaozhang Village on the east side of the Xiachuan Village, with an altitude about 1600 meters. A total of two squares with similar stratigraphic accumulation were excavated at Loc. Shuijingbei, and the strata accumulation can be divided into two major cultural stages, of which the former cultural layer consists of abundant remains dominated by simple core-flake technology corresponding to the early Upper Paleolithic period (44,000~33,000 years ago), the latter cultural stage contains microblade technology remains corresponding to the middle Upper Paleolithic period (26,000-25,000 years ago).

The raw materials of stone artifacts unearthed from QX2015T4 square is dominated by chert, followed by vein quartz, and occasionally agate and quartzite. The stone nodules are relatively broken, which probably results in the small size of the stone artifacts. A variety of stone artifacts were obtained from the former cultural stage including cores, blade cores, blades, flakes and various tools such as sidescrapers, pièces esquillées, denticulates, points, and backed segments. The dominant technology type of this stage is the simple core-flake technology, most artifacts were directly knapped by hard hammers with a small number of artifacts using bipolar method. The cores see two major flaking organization strategies guided by the platform and the flaked surface, among which the more primitive platform-oriented flaking idea is the mainstay. Based on the characteristics of platform retouch, maintenance of the side edge of the flaked surface, and bottom edge retouch of the control flaking range were observed of the blade core, it is suggested that the emergence of blade technology in the early Upper Paleolithic period.

The stone assemblage from the latter stage in QX2015T4 can be described as a typical microblade technology. The cores appear to be a more advanced flaked surface-oriented flaking idea, the platform retouch method became more mature and common, and the application of bipolar debitages method decreased significantly. Although sidescrapers are the most common tool type, there are typical Upper Paleolithic tools such as endscrapers. Even if the number of blade technology products seen in the upper culture layer is small, relatively clear blade technology characteristics can still be recognized. On the whole, from the characteristics of former cultural stage to the latter cultural stage, the simple core-flake technology has continued for two time periods, but its notable development has been seen in the later stage, with the blade technology have also developed steadily simultaneously, until the final mature microblade technology appeared and developed in middle Upper Paleolithic period.

Comparing with the contemporaneous sites in North China, Altai region of Russia, Lake Baikal region and Gobi region of Mongolia, it is proposed that the technical factors of blades and certain tool types such as backed segments and points seen in the early Upper Paleolithic period of this square might be related with the many times migration flow of people during the MIS3 stage. However, due to the influence of climatic conditions and the long-term continuation of the simple core-flake tradition in North China, blade technology has not been able to occupy the mainstream. There are at least 3000 years’ interval between the microblade technology appeared during the middle Upper Paleolithic period is at least old and remains in the earlier stage, however, certain similarities were observed including the morphology and flaking method of blade cores and microblade cores, and the connection between the two types of technologies still needs more materials for in-depth discussion.

In summary, the progress characteristics of simple core-stone flake technology from the early to middle Paleolithic stage are observed from this square, and it is speculated that there may be blade technical factors in the early Upper Paleolithic period, which provides a new idea for rethinking the source of the microblade technology system in the middle Upper Paleolithic period in North China.