SCIENCE Earth Sciences • • ...... RESEARCH PAPER ...... https://doi.org/10.1007/s11430-017-9257-3

Human activity during the late Pleistocene in the region, northwest China: Evidence from a buried stone artifact Kangkang LI1,2,3, Xiaoguang QIN1,2*, Xiaoyan YANG4, Bing XU1,3, Lei ZHANG1, Guijin MU5, Dong WEI6, Chunxue WANG6, Yong WU7, Xiaohong TIAN7, Yongchong LIN5, Wen LI5, Jiaqi LIU1,3 & Yinxin JIAO8

1 Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 2 CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China; 3 University of Chinese Academy of Sciences, Beijing 100049, China; 4 Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; 5 Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; 6 School of Archaeology, Jilin University, Changchun 130012, China; 7 Xinjiang Institute of Archaeology, Urumqi 830011, China; 8 Bureau of Cultural Heritage of , Ruoqiang 841800, China

Received November 14, 2017; revised July 2, 2018; accepted August 8, 2018; published online September 19, 2018

Abstract The Lop Nur region, in the east part of , was an important transportation junction between west and east, north and south Eurasia. However, previous studies on prehistoric human activity have concentrated mostly on the , whereas that during the Stone Age remains largely unresearched. Here, we present a new direct evidence of human activity in the late Pleistocene, recorded on a grinding stone buried in a lacustrine sediment section of the Lop Nur region. The grain size distribution of the sediment section indicates that the site was probably in the center of a lake with weak hydrodynamic environment. Therefore, the stone artifact can only be carried to here by people instead of river and it was never move as soon as left here. Results of radiocarbon dating, the evident stratigraphic relations between the stone artifact and the sedimentary formation, indicate that the human activity could extend to approximately 13 ka BP. Furthermore, the results of starch-grain and use-wear analyses suggest that ancient humans gathered seeds of Triticeae, roots, and tubers and used the grinding stone to simply process selected plant as plant foodstuffs during this period. It implies that the environmental conditions in the river delta of the Lop Nur were inhabitable during the late Pleistocene. Keywords Lop Nur, Late Pleistocene, Stone artefact, Human activity, Paleo-environment

Citation: Li K, Qin X, Yang X, Xu B, Zhang L, Mu G, Wei D, Wang C, Wu Y, Tian X, Lin Y, Li W, Liu J, Jiao Y. 2018. Human activity during the late Pleistocene in the Lop Nur region, northwest China: Evidence from a buried stone artifact. Science China Earth Sciences, 61, https://doi.org/10.1007/ s11430-017-9257-3

1. Introduction catchments, with only a few Paleolithic human activity sites reported in Xinjiang (Zhang, 1997; Liu, 2012; In China, the study of Paleolithic archaeological sites of the Zhu and Gao, 2015). Furthermore, the ages of these Paleo- late Pleistocene has focused mainly on the Yangtze River and lithic archaeological sites, such as the Jirigale site in the Tashkurgan River, Luotuoshi site in Tacheng, stone tool sites located at the southern margin of the Tarim basin, and the * Corresponding author (email: [email protected])

© Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018 ...... earth.scichina.com link.springer.com 2 ...... Li K, et al. Sci China Earth Sci ...... 2

Gouxi site in the Turpan (Huang et al., 1988; Zhang, 1997; activities in the Lop Nur region. We analyzed the chronology Shui, 2008; Derevianko et al., 2012; Zhu and Gao, 2015), and sedimentary facies of the section, combined with the were simply estimated according to geomorphology or stone remains of starch grains and use-wear recorded on the tool typology. The Tongtian Cave in Altay prefecture was the ground stone, with the aim of providing new direct evidence first Paleolithic site to be well-dated, with the 14C age of for early human activity in this region. Paleolithic culture deposition being approximately 45 ka (Yu, 2018). The Lop Nur region (Figure 1), located in the easternmost 2. Description of sample part of the Tarim basin in Xinjiang, China, was an important transportation junction between East and West Asia, Mongol Lake Lop Nur is the terminal lake of the ancient Plateau, and Qinghai-Tibet Plateau (Wang, 1996). Ancient and the Kongque River in the geological period, with the Lop human activity, centered on the west bank of Lake Lop Nur, Nur region being the arid core of Eurasia. The annual pre- has been attracting much attention (Chen, 1936; Wang, cipitation is approximately 20 mm, whereas evaporation 1983a, 1983b; Hou, 1984; Bergman, 2013; Jia et al., 2011; reaches above 3000 mm (Xia et al., 2007), resulting in a Qin et al., 2011; Zhang J P et al., 2012; Yang et al., 2014; Xu thick salt crust in the dried-up lake area. The ground surface et al., 2017). However, only the Xiaohe Culture of the is strongly eroded by the prevailing northeasterly wind to Bronze Age and the Loulan Culture of Han-Jin Dynasties form a yardang landform around the lake (Xia et al., 2007). (Xia et al., 2007) are known well, with the latest report in- Consequently, the salt crust and yardang dominate the dicating human activity during Yuan-Ming Dynasties in landscape of the region (Dong et al., 2012; Lin et al., 2018). Loulan area (Li et al., 2018). Numerous stone artifacts have The ground stone site is located 6.65 km southwest of the been found in the area, which are speculated to date from 10 ancient Loulan city site named as LA by Stein (1921). An ka BP using only by archaeological typology, as suitable ancient river channel registered as South River No.1 because dating material is not available (Xia et al., 2007). Conse- it is the first river from west to east in the south of the LA, quently, possible Paleolithic human activity in the Lop Nur lies approximately 1.5 km to the north of the ground stone region remains unexplored. However, in our scientific in- site. Many dead Populus Euphratica trees and a few with- vestigation, we found a ground stone artifact buried in la- ered reed roots remain on the top of yardang in the area. The custrine sediment, providing a new clue to ancient human remnants of stone tools, pottery, bronze, and ironware are

Figure 1 Location of study region. The red star indicates the site of stone artifact, while triangles are ancient ruins, and LA is the ancient Loulan city (Stein, 1921). The cyan Lake Lop Nur was dried in 1972 (Xia et al., 2007). Remote sense image is from www.ovital.com. 3...... Li K, et al. Sci China Earth Sci ...... 3 often found on the ground nearby. placed in 10%H2O2 liquid to remove organic matter, after The ground stone had been buried in lacustrine sediment which deionized water was added to the samples, and they (Figure 2), and is black, irregular cuboid sandstone, with were left to stand overnight. After rinsing with distilled −1 length 28 cm, width 9–10 cm, and thickness 3 cm (Figure 3). water, 10 mL of 0.05 mol L dispersant (NaPO3)6 was One end of the sandstone, approximately 9 cm long, had poured into the sample liquid. The samples were stirred for been exposed to the outside. The six surfaces of the ground 10 min using an ultrasonic agitator. The size analysis was stone were coded SMP01–06, and the characteristics of each conducted with a Master Size 3000 Laser Particle Size face are outlined in Table 1. There is an unbroken vertical Analyzer, with a measuring size ranging from 0.01 to crack in surfaces SMP 01–02. The surface of SMP04 is 3500 μm. uneven and extremely rough, and may be a broken crack surface. As there is a clearly visible and smooth arc on the 3.2 Chronology surface of SMP02 (Figure 3), probably because of use, it is speculated that this ground stone was used as a grinding Three samples from the study section (TS04, TS05, and stone. TS16, with respective depths of 10, 65, and 70 cm) (Table 2) were chosen for radiocarbon dating by accelerator mass spectrometry (AMS) in Beta Analytic Inc., United States. 3. Methods The sample pretreatment was utilized to extract organic matter with the pickling method, and then the 14C age will be 3.1 Grain size calibrated by the isotope fractionation (Reimer et al., 2013). The grain size distribution of sediments can serve as a useful The calibration of the calendar was obtained by using the proxy of depositional environment (Yin et al., 2008, 2009). INTCAL13 database of Calib7.0.4 software. We conducted grain size analysis of the study section to help us understand sedimentary environment and hydrodynamic 3.3 Stone artefact function condition at the time, and to ascertain whether the stone artifact was an autochthonous deposit or had been trans- As stone artifacts are the material carrier of human actions, ported by river or flood, that have influenced site formation analyzing the function of such artifacts is a key to understand and modification. The thickness of the lacustrine section, the cognitive abilities and the living environments of ancient composed of yellow silty clay, is 85 cm (Figure 2). The humans. Recovering starch grains and analyzing the use- section was sampled at interval of 5 cm, and 17 samples were wear of archaeological artifact surfaces have been applied collected. The ground stone was located at 70 cm depth. The successfully to study the functions of such stone artifacts yardang with the stone tool is not the highest, and the height (Shen and Chen, 2001; Gao and Shen, 2008; Guan and Gao, of the surrounding yardangs is usually less than 2 m. 2009; Yang et al., 2009; Zhang et al., 2010a; Liu et al., 2010, The pretreatment of samples followed a standard method 2011, 2013). Starch residue analysis refers to the extraction introduced by Qin et al. (2005, 2015). First, the samples were and identification of residual starch granules on the stone

Figure 2 Outcrop with the stone artifact, and medium grain size curve of the study section. Black triangles are indicate the location of accelerator mass spectrometry (AMS) 14C dating. 4 ...... Li K, et al. Sci China Earth Sci ...... 4

Figure 3 Photographs of stone artifact. (b) is the enlarged image of site 1 in (a), site 2 in (c) is the position for use-wear analysis see below.

Table 1 Characteristics of the stone artifact and starch grainsa) Face/sample number Characteristics of face Number of starch grains SMP01/T1 Smooth, visible fissure, 1/3 exposed to outside 1

SMP02/T2 Smooth, dip angle of arc approximately 4°, probably used facet of stone tool, visible fissure, 1 1/3 exposed to outside SMP03/T3 Long side, smooth, 1/3 exposed to outside – SMP04/T4 Long side, uneven and rough, probably a broken crack surface 4 SMP05/T5 Short side, flat, entirely buried 3 SMP06/T6 Short side, edges and corners, entirely exposed – S1–S5 Samples of clay adhering to surfaces SMP01–05 – a) * T1–T6 are ultrasonic shocked exaction samples, S1–S5 are samples of clay adhering to SMP01–05, “–” means no retrieved starch grains from the corresponding face

Table 2 Radiocarbon results of study sectiona) Conventional 14C Calibrate age Median calibrate age Sample No. Depth (cm) Material * age (a BP) (2σ, 95.4%) (cal a BP) (2σ, 95.4%) (cal a BP)* TS16 10 bulk organic 11950±40 12756–12677 12716±40 TS05 65 bulk organic 13500±40 14688–14132 14410±40 TS04 70 bulk organic 12340±40 13139–12997 13068±40 a) * results that have been calibrated by using the carbon reservoir age 1140 a of Lake Bosten artefact to analyze human behavior, prehistoric human diets, We followed the experimental method of use-wear analy- and the paleoenvironment (Piperno and Holst, 1998; Piperno sis by Zhang et al. (2010a, 2010b), using a Nikon SMZ 1500 et al., 2004; Yang et al., 2006, 2009, 2012; Barton et al., microscope, to observe the damage and wear marks. To de- 1998; Barton, 2007; Li et al., 2010; Guan et al., 2014). Use- termine whether the ground stone had been used to grind wear analysis is to make microscopic observation of stone plant materials, we performed starch grain analysis on the artefact, and analyze the subtle use traces left on the surface artifact. Furthermore, to determine whether the starch grains to determine its function (Shen and Chen, 2001). derived from the use of the tool or sediments, we obtained 5...... Li K, et al. Sci China Earth Sci ...... 5 clay sediment samples adhering to the stone tool surfaces and ultrasonic-shocked extraction samples of the artefact sur- faces, respectively, following the method of Barton et al. (1998). Extraction of starch grains: Firstly, The clay sediments are removed carefully from each surface of the artefact (except SMP06) by a knife. The five samples were numbered S1–S5. The sediment surrounding the artifact was numbered S6. Subsequently, after rinsing the artifact and removing the surface clay, each surface of the artifact was shaken in an ultrasonic bath for 10 min to dislodge adhering sediment and starch completely. Six samples were obtained and numbered Figure 4 Grain size distribution of studied section. T1–T6. Starch grains were isolated by adding a heavy liquid solution of CsCl, with a density of 2.0 g cm−3. The recovered residue was mounted in glycerin and water on a slide and sediment for calibration. Lake Bosten is the source of the examined with polarized and un-polarized light at a power of Kongque River, one of the major tributaries of the ancient 400× power with the starch-specific extinction cross. For a Tarim Rivers flowing into Lop Nur. Therefore, we could use detailed protocol, see Piperno and Holst (1998), Piperno et the 1140 yr reservoir age of Lake Bosten (Chen et al., 2006; al. (2004). Huang et al., 2009), which is a high reservoir age for lakes in Starch grain identification: Our starch keys and classifi- Xinjiang (Zhang J F et al., 2012), to maximize the calibration cations emphasized mainly attributes including: (1) overall of the 14C ages of the study section. The ages of the top and grain type and shape, (2) contour and surface features, (3) the bottom of the section are approximately 12.7 and 13 cal position and form of the hilum (the botanical center of the ka BP, respectively, although the age of TS04 and TS05 is starch grain) and fissure, (4) number and characteristics of reversed. Accordingly, it was confirmed conservatively that pressure facets present on compound grains, and (5) presence the stone artifact was discarded by ancient humans in the or absence of demonstrable lamellae (Piperno and Holst, lake during the late Pleistocene, at approximately 13 cal ka 1998; Piperno et al., 2004). We compared these with starch BP. grains from modern plant samples (Yang et al., 2005, 2009, 2010, 2012). 4.2 Starch grains and use-wear

4.2.1 Starch grains 4. Results Nine starch grains were yielded from T1–T6 (Table 1; Figure 5), but no starch grain were retrieved from S1–S6, strongly 4.1 Depositional environment and chronology suggesting that starch grains did not come from lacustrine The dominant mode of grain size distribution in the study sediments. The retrieved starch grains can be divided into section is 1–10 μm (Figure 4), suggesting that the sediment three groups, as follows. sequence was the deposition at the center of lake with weak Group A (Figure 5a–c): We retrieved three circular or sub- hydrodynamic condition by following the analysis of grain circular starch grains with the same characteristics as the size of samples from different sedimentary facies (Yin et al., seeds of Triticeae. The grains had centric and faint hila, 2008, 2009), probably corresponding to a period with pronounced lamellae, and an X-shaped cross extinction. The abundant water in Loulan delta. size of the major axis is 22.9–25.97 μm. Triticeae includes The lacustrine sediment sequences of Lake Lop Nur re- the following plants: Leymus chinensis, Aegilops tauschii, corded the changes in the paleoenvironment of the region, Agropyron cristatum, Secale cereale, Hordeum vulgare var. and the chronology relies mainly on radiocarbon dating (Yan Nudum, Triticum aestivum, and Hordeum vulgare, and oth- et al., 1983; Yan et al., 1998; Ma et al., 2008; Jia et al., 2017a) ers. A more specific designation could not be determined in and optically stimulated luminescence (OSL) dating (Wang this study, as the starch grains are quite similar. et al., 2008; Qin et al., 2011; Liu et al., 2016). In this study, Group B (Figure 5d–g): Four sub-round or polygon starch dating was carried out on organic matter of bulk sediment grains were retrieved from the stone tool. They have centric, due to lack of plant remains. Usually, 14C ages of lake should close hila, faint lamellae, and a linear or Y-shaped fissure. be adjusted to eliminate the effect of radiocarbon reservoir The length range of the major axis is 13.1–21.05 μm. The effects (Zhang J F et al., 2012; Mischke et al., 2017). starch grains are comparable to those of modern tubers or However, Lake Lop Nur had dried up in 1972 so that we roots. Three grains (Figure 5d–f) could be the starch grains of could not establish 210Pb and 137Cs chronology by surface Fallopia multiflora, whereas another (Figure 5g) could not 6 ...... Li K, et al. Sci China Earth Sci ...... 6

Figure 5 Starch grains recovered from stone tool. (a)–(i): Starch grains; (a′)–(i′): starch grains under polarized light. be identified. Last Glacial Maximum (18 ka BP) to the Holocene. The late Group C (Figure 5h–i): Two starch grains were retrieved Pleistocene at approximately 13 cal ka BP was in the last that have a spherical or a polygonal shape, with the major deglaciation, i.e., the transitional period from cold glacial to axes measuring 21.04 and 19.72 μm, respectively. We were warm interglacial. Several short-term climatic events oc- unable to identify these grains because of poor preservation. curred during the last deglaciation (Dansgaard et al., 1989; Liu et al., 2009; Shakun et al., 2012). The climate variability 4.2.2 Use-wear around Lop Nur was obviously also controlled by the global The results of use-wear analysis revealed evident and typical climate change (Luo et al., 2009; Jia et al., 2017a, 2017b; features related to the grinding act in SMP02 (Figure 6). Wang et al., 2008). However, the low extent of grinding could indicate that the A humid environment during 13000–12700 yr BP in- artifact had not been used for long time. dicated by geophysical, geochemical, and paleobotany properties of lacustrine record of Lake Lop Nur (Luo et al., 2009; Yang et al., 2013). Herbs were dominant throughout 5. Discussion the Late Pleistocene, and Gramineae were relatively abun- dant, as indicated by palynology (Yan et al., 1998; Jia et al., 5.1 Environmental conditions of the Lop Nur region in 2017a), with the pollen of Typha and reed being found often late Pleistocene (Yan et al., 1998; Yan et al., 1983). There was abundance The global climate experienced dramatic changes from the water recharge and a developed wetland on the bank of Lake

Figure 6 Use-wear on the artifact (see the site 2 in Figure 3c). 7...... Li K, et al. Sci China Earth Sci ...... 7

Lop Nur (Yan et al., 1998), indicating a relatively wet en- pits and interstitial crevices in the surface during processing, vironment during the late Pleistocene. were retrieved from the rough surface of SMP04 as the fis- The Tarim Basin is surrounded by actively uplifted sure and rough surface trapped and survived more starch mountains, such as the Kunlun Mountains and the Altyn grains. Moreover, starch grains were not retrieved on the Mountains to the south and the Tianshan Mountains to the SMP06, indicating that strong wind erosion was not con- north. The hydrological changes depended entirely on ducive to the preservation of the starch grains. meltwater from glaciers and snow, as well as orographic The results of AMS14C dating indicated the age of the rainfall, and oases existed along rivers at approximately 13 grinding stone left by ancient humans as late Pleistocene, ka BP (Wen and Qiao, 1995; Zhou et al., 1996; Yang, 2001; approximately 13 cal ka BP. Piperno et al. (2004) noted that Liu and Qin, 2005). As Lop Nur is the lowest place of the the grinding stone artifacts were probably used to pound and Tarim Basin and an amount of meltwater or topographical grind hard and fibrous plant seeds into easily digestible rainfall from surrounding mountains flowed into the lake foodstuffs at that time. The major types of starch grains re- during the late Pleistocene, the studied section could be the trieved from the stone tool were Triticeae, roots, and tuber deposition in the period, meaning that the Loulan delta area plants, implying that ancient human in the region had gath- on the west bank of Lake Lop Nur probably was an in- ered some seeds, roots, and tubers as plant foodstuffs at habitable oasis, where abundant edible plants grew. approximately 13 cal ka BP. Previous researchers have found some cultivated Grami- 5.2 Human activity neae pollen from the lacustrine sediment in the center of the dried-up Lake Lop Nur, arguing that farming activities could The British explorer, Aurél Stein, who investigated the have taken place here during 10–5 ka BP (Jia et al., 2011). Loulan area, collected various stone artifacts (microblade These could well be the continuation and development of the and arrowhead), and put forward the simple view that “the plant utilization activity in the late Pleistocene. However, site inhabited time could be traced back to the early Stone identifying the relationship between the gathered plants in Age” (Xia et al., 2007). Subsequently, other scholars col- the late Pleistocene and cultivation in the early Holocene lected more artifacts laid in ground during field investigation requires more evidences. (Bergman, 2013; Loulan archaeology team of Xinjiang, 1988; Niu, 2004; Xia et al., 2007) and Hou (1984) suggested 5.3 Relationships between strata and relic that the Loulan ancient city could be the center of human activity in the Kongque River delta during Stone Age; The Lop Nur region has been eroded strongly by the north- however, the specific time of human activity is rarely men- easterly wind, and the west bank of the lake is dominated by tioned. The stone artifact buried in the sedimentary forma- the NE-trending groove-ridge terrain, i.e., the yardang tion has evident stratigraphic relations, namely, the age of the landform. The height of most yardang ridges is 1–3 m, but sediment formation could be considered to represent the time the depths of the eroded depressions could exceed 10 m. The of human activity. Therefore, the human activity in the Lop top of most yardangs is not the top of the lacustrine sediment Nur region could extend to 13 ka BP. and the original ground surface during the ancient Loulan The grain size distribution, lack of saltation and coarse period. Only the top of the highest yardang, on which reed suspended particles of the studied lacustrine section (Figures residues usually remained, represents the original ground 2 and 4), indicate weak hydrodynamic environment in the surface. Previous study has revealed a sedimentary dis- center of the lake, suggesting that the stone artifact can only continuity surface at the lower part of the Holocene sediment be carried to here by people instead of river and it was never section under the pagoda of Loulan City, indicating that the move as soon as left here. Furthermore, the clay sediment area had been strongly wind-eroded during a dry event be- samples did not yield any starch residues, but nine grains tween 8–9 ka BP (Jia et al., 2010; Qin et al., 2011) and this were identified from ultrasonic-shocked extraction samples. was also the yardang landform developed period. Based on these results, we believe that the starch residues During the investigation, it was noticed that the grey, loose originate from the stone artifact being used by ancient hu- sediments of an adjacent and higher yardang mound were mans for grinding. Lü (2002) claimed that the number of obviously different from those of the yardang where the starch grains recovered from artifact due to conditions of grinding stone had been buried. This suggests that these buried. The lacustrine environment was not conducive to the yardangs are not a set of continuous sedimentary strata. A preservation of the starch residue in this paper. Most of re- discontinuity eroded surface between two yardangs, which sidual starch grains on the stone artifact could have been could have developed during the dry event in 8–9 ka BP, was washed off by the lake water; therefore, only a few starch found in the Loulan pagoda section. During this wind-eroded grains were retrieved from the artifact surfaces. Approxi- dry period, the ground surface developed into the rough mately half of the starch grains, which were embedded tiny yardang landform. After the ending of the dry period, later 8 ...... Li K, et al. Sci China Earth Sci ...... 8 sedimentary deposition was overlain on the early remodeled Zhang Xiaoling are thanked for assistance with the use-wear analyses, and sediment strata, leading to the difference between the sedi- thanks Cui Yousheng and Ren Hui for helping in field investigation and drawing. This work was supported by the Ministry of Science and Tech- mentary strata of two adjacent yardangs mounds. 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