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Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China
Quaternary International xxx (2014) 1e7
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Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China Xuefeng Sun a, *, Huayu Lu a, Shejiang Wang b, Richard Cosgrove c, Wenchao Zhang a, Kaifeng Yu a, Haixin Zhuo a a School of Geographic and Oceanographic Sciences, MOE Key Lab of Coast and Island Development, Nanjing University, Hankou Road 22, 210093 Nanjing, China b Joint Laboratory of Human Evolution and Archaeometry, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China c Archaeology Program, School of Historical and European Studies, La Trobe University, Victoria 3086, Australia
a r t i c l e i n f o
a b s t r a c t
Article history: Available online xxx
The Luonan Basin contains thousands of stone artifact scatters located in the upper drainage of South Luo River, central China. Despite many years of survey, the age of these Paleolithic artifacts remained uncertain. In 2007, our team established for the first time a chronological framework for the natural loess deposit at locality 1, at the site of Liuwan. Here we report on two in situ artifact assemblages buried in loess deposit which were excavated at Liuwan localities 2 and 3 in 2009. The characteristics of these two Paleolithic assemblages are similar: the stone artifacts are small, and include stone hammers, cores, flakes, chunks, debris, and a small number of retouched tools, represented primarily by scrapers and points. We dated the loessepaleosol sequences at the two new localities, established chronology on the basis of stratigraphic analysis and comparison of magnetic susceptibility profiles between localities 1, 2, and 3, and the typical loessepaleosol time series. Our results suggest that the artifact bearing layer 2 at locality 3 is in the S5 SS2 paleosol unit, dated to between 575 and 568 ka; the artifact bearing layer 1 at localities 2 and 3 is in the soil unit S5 SS3 dated to between 625 and 581 ka. This result suggests that hominin occupation of the Luonan Basin occurred between 625e581 ka and 575e568 ka, there is a probable change in raw materials exploitation from vein quartz in the artifact layer 1 to a mixed vein quartz and quartzite in the artifact layer 2. The Liuwan site is chronologically similar to the Qiaojiayao site in the middle of South Luo River, and indicates that the hominins ranged widely in the Qinling Mountains during the Middle Pleistocene. Ó 2014 Elsevier Ltd and INQUA. All rights reserved.
Keywords: Middle Pleistocene Luonan Basin Loess Magnetic susceptibility Stone artifacts
1. Introduction Research has shown that the Luonan Basin is an important locality for understanding middle Pleistocene hominid occupation and settlement (Wang, 1986; Wang and Huang, 2001; Wang et al., 2004, 2005a, b, 2011; Lu et al., 2007, 2011a; Sun et al., 2013.), but the age of Luonan Paleolithic assemblages are still unclear. The nearby region contains a number of important early and middle Pleistocene archaeological deposits such as those from Lantian (Jia et al., 1966; An and Ho, 1989), Dali (Wang et al., 1979; Xiao et al., 2002; Yin et al., 2011), and Xihoudu sites (Zhu et al., 2003) (Fig. 1). Since the 1980s, investigations in the Luonan Basin have
* Corresponding author. E-mail address: [email protected] (X. Sun).
focused on the analysis of stone artifacts and their potential age but this has been hampered by the lack of suitable datable contexts (Wang, 1986; Xue, 1987; Wang et al., 2005a, b, 2008; Shaanxi Provincial Institute of Archaeology et al., 2007). In the most comprehensive investigation by Wang et al. (2004), the lithic artifacts excavated from Longyadong Cave have been the only ones systematically studied (Shaanxi Provincial Institute of Archaeology and Museum of Luonan County, 2008; Sun et al., 2013). The Luonan Basin is an intermountain depression with an elevation of 993 m, and is located in the upper drainage of South Luo River, eastern Qinling Mountains, central China (Fig. 1). It is regarded as the physical boundary between southern and northern China. The basin has an annual precipitation of 706 mm and an average annual temperature of 11.0 C, and a mosaic of grass, reforestation, and endemic plant communities covers the area. Loess sediment containing distinct loessepaleosol alternations was
http://dx.doi.org/10.1016/j.quaint.2014.04.061 1040-6182/Ó 2014 Elsevier Ltd and INQUA. All rights reserved.
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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X. Sun et al. / Quaternary International xxx (2014) 1e7
Fig. 1. Location of Liuwan archaeological site in Luonan Basin, upper South Luo River, central China and the related archaeological sites in adjacent regions.
deposited on terraces of the South Luo River in the Luonan Basin with thicknesses ranging from 1 to 25 m (Lu et al., 2007, 2012; Zhang et al., 2012). Surface scatters of Paleolithic artifacts are found on various landforms across this basin and good examples of in situ lithic artifacts occur at the Liuwan and Shangbaichuan sites (Lu et al., 2007, 2011a). The Liuwan site is situated on the second river terrace (Fig. 2), on the east bank of Maping River that flows into the South Luo River, 6 km north of the town of Luonan (Fig. 1). The Shangbaichuan site is also located on the second terrace of the Shimen River that flows into the South Luo River, 10 km south of the town of Luonan. The thick loessepaleosol deposit covers a series of fluvial sands, pebbles, and cobbles, which derived from the paleoriver channel. Excavation by local brick-makers has exposed a thick section of well-preserved loess and this has revealed many stone artifacts that were collected. At both sites, samples for optically stimulated luminescence (OSL) dating, magnetic susceptibility and paleomagnetic analyses were collected that established a timescale for these two loessepaleosol sequences (Lu et al., 2007, 2011a). To further refine the chronology, we conducted a detailed geological and archaeological survey at the Liuwan site in the summer of 2009, identifying layers containing in situ stone artifacts
in newly exposed loess sections (Fig. 3a, b, c). These sections are designated Liuwan localities 2 and 3. Two small (100 200 cm) test trenches (A and B) were dug at localities 2 and 3 where a total of 76 artifacts are excavated from a 5 cm thick horizon in trench A and 140 artifacts are unearthed in trench B, respectively. Artifact layer 1 lies w160 cm above layer 2 (Fig. 3b). Locality 1 is about 60 m southeast of locality 2, and locality 2 is about 40 m southeast of locality 3. The discovery and dating of these two artifact layers at Liuwan site should be meaningful for better understanding the age of hominid evolution in Luonan Basin.
2. Sampling, measurement, and stratigraphic analyses At Liuwan localities 2 and 3, samples were taken for magnetic susceptibility at an interval of 5 cm, yielding 270 bulk samples; fifty northerly-aligned cubic samples (2 2 2 cm3) were taken from locality 2 and locality 3 for paleomagnetic stratigraphic analysis. A Bartington MS-2 magnetic susceptibility meter was used to assess the magnetic susceptibility, and the paleomagnetic measurement was carried out using the 2G superconductor magnetometer at Nanjing University.
Fig. 2. Section of the Maping River terraces in which the artifact localities 1, 2 and 3 are located. The position of artifact layer 1 and 2 within the loessepaleosol section are indicated.
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
X. Sun et al. / Quaternary International xxx (2014) 1e7
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Fig. 3. (a) Loessepaleosol section in locality 1; (b) The test excavation trench B in locality 3. L5 is clearly identified; (c) in situ artifacts discovered in the newly exposed loess section in locality 3.
For the magnetostratigraphic analysis, inclinations of all of the samples from localities 2 and 3 are positive, demonstrating that the loess was deposited in the Brunhes positive magnetic chron (N1) (Fig. 5), indicating that the loess deposits are younger than 0.78 Ma (Cande and Kent, 1995). These sediments were formed in the middle to late Pleistocene, chronologically similar to that of locality 1. The important point for this study is that the loessepaleosol stratigraphy in this area is uniform. Pedostratigraphic observation shows that L5 (the 5th loess unit in the typical Chinese loess sequence) is more prominent than the others and it is easily recognizable (Fig. 3a and 3b). At locality 2, the loess section is 8.5 m thick with five loess units and six paleosol layers. Based on the magnetic susceptibility variation between localities 1 and 2 and the field observations at locality 2, the loessepaleosol deposit here is identified as S1, L2, S2, L3, combined S3eS4, L5, S5 SS1 (SS ¼ sub soil), S5 LL2 (LL ¼ sub loess), S5 SS2, S5 LL3 and S5 SS3, respectively (Fig. 5). By comparing the magnetic susceptibility, the loess stratigraphy at these two localities appears identical. At locality 3 the loess deposit is only 5 m thick and three loess units and four paleosol complexes can be identified. Comparison of magnetic susceptibility and using L5 layer as a prominent marker, we conclude that the loessepaleosol sequence in locality 3 is similar to locality 2, with a combined S3eS4, L5, S5 SS1, S5 LL2, S5 SS2, S5 LL3, and S5 SS3 sequence (Fig. 5). Unfortunately the upper part of the loess section in locality 3 was eroded or disturbed. There is a distinct shift in the magnetic susceptibility below the S5SS1 soil unit in locality 1, 2 and 3. The magnetic susceptibility varies greatly above the S5SS1 soil, but below it is
relatively stable and consistent. This is different from the magnetic susceptibility recorded in the loessepaleosol sequence of central Chinese Loess Plateau (Fig. 5). Though below S5 SS1 the magnetic susceptibility is stable, but two close paleosol complexes were distinguished. So we deduced they are S5 SS2 and S5 SS3. For no negative paleomagnetic data found, the last paleosol at the bottom maybe S6 or S7. The reason for the abrupt shift may be that the magnetic susceptibility varies according to different temperature-moisture levels since ferromagnetic minerals will be destroyed under high moisture (waterlogged), pedogenic conditions (Zhao et al., 2008; Ao, 2010; Ao et al., 2010; Lu et al., 2011b; Sun et al., 2012). However, field observations of the paleosol units below the S5SS1 show the soil was clear and well developed suggesting that the magnetic susceptibility can still identify loess and paleosol units. 3. Paleolithic assemblages In trench A of Liuwan locality 2, artifact layer 1 is between 755 and 760 cm in depth (Fig. 6) and yielded 76 artifacts. It is comprised of scrapers, flakes, cores, debris, and chunks (Table 2 and Fig. 4a). In trench B at Liuwan locality 3, artifact layer 2 is between 305 and 310 cm deep from which 107 artifacts were excavated made up of scrapers, points, stone hammers, flakes, cores, debris, and chunks (Table 2 and Fig. 4b). Artifact layer 1 is located at a depth of 445e 450 cm (Fig. 6) and contains 33 artifacts including scrapers, points, stone hammers, flakes, debris, and chunks (Table 2). Paleolithic assemblages from Liuwan locality 2 and 3 are similar technologically (Table 2 and Fig. 4a, 4b).
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Table 1 Ages of the loessepaleosol sequence at Liuwan locality 1 (reference to Heslop et al., 2000). Stratigraphy
Depth (m)
Age (ka)
Soil L1 S1 L2 S2 L3 S3 & S4 L5 S5SS1 S5SS2 S5SS3 L6? S6?
0e0.50 0.50e1.20 1.20e2.30 2.30e3.05 3.05e3.55 3.55e4.05 4.05e5.50 5.50e6.00 6.00e8.20 8.20e9.40 9.40e10.10 10.10e11.80 11.80e12.50
e 10e71 79e129 129e196 196e250 250e290 290e417 417e503 503e556 568e575 581e625 e e
Table 2 Lithic artifact assemblages of two culture layers at Liuwan localities 2 and 3. Type Trench A e artifact layer 1 Scrapers Flakes Cores Debris Chunks Total Trench B e artifact layer 2 Scraper Point Stone hammer Flakes Cores Debris Chunks Total Trench B e artifact layer 1 Scraper Point Stone hammer Flakes Debris Chunks Total
Quantity
%
3 5 4 9 55 76
3.95% 6.58% 5.26% 11.84% 72.37% 100.00%
5 4 1 12 3 47 35 107
4.67% 3.74% 0.94% 11.21% 2.80% 43.93% 32.71% 100.00%
2 1 1 4 6 19 33
6.06% 3.03% 3.03% 12.12% 18.18% 57.58% 100.0%
4. Ages of Liuwan stone artifacts The magnetic susceptibility values of loessepaleosol sequences are high in soil and, low in loess units (Heller and Liu, 1984; Liu, 1985). These values are regarded as a good proxy of prevailing paleoclimatic conditions (Liu and Ding, 1998). The chronological sequence for the typical loess deposit of the Quaternary has been firmly established (Lu et al., 1999, 2004). These can be used to constrain the ages of the other loess deposits where they occur across north China. Magnetic susceptibility serves to distinguish soil and loess units and provides a clear record of climatic changes between the warmewet and coldedry that was dominated by Asian monsoon circulations in the Luonan Basin (Lu et al., 2007, 2011a). Therefore, we can compare the newly obtained magnetic susceptibility sequence of Liuwan sites with the independently controlled loessepaleosol time series to obtain ages for these new sequences that provides a robust chronological framework. At Liuwan locality 1 the loess section is 13 m thick with eight loess units and eight paleosol complexes. On the basis of four OSL ages (E. 146.6 12.3 ka, F. 137.0 13.4 ka, G. 151.6 4.9 ka, and H. 202.2 6.9 ka) (Fig. 5), the first and second paleosol units correspond to the S1 paleosol in central Chinese Loess Plateau, with an age 79e129 ka. The third paleosol unit correlates to the S2 soil that has an age of 196e250 ka while the fourth paleosol unit of S3 and S4 complex has an age of about 290e417 ka. The fifth, sixth, and seventh paleosol units were S5 SS1 (503e556 ka), S5 SS2 (568e 575 ka), and S5 SS3 (581e625 ka) soils, respectively (Table 1). On the basis of the magnetic susceptibility results and field observations, there is a clear correlation between the localities 1, 2, and 3. The oldest artifact layer in locality 2 and 3 is from the same layer and dates to the same time. Correlations with the Luochuan loessepaleosol sequence suggest that the paleosol containing the artifacts in layer 1 is within the S5SS3 soil, with a corresponding age of between 581 and 625 ka. The paleosol unit containing artifact layer 2 is located in the S5 SS2 soil dated to between 568 and 575 ka (Lu et al., 1999, 2004) (Fig. 5). As the S5 soil was formed during the Quaternary climatic optimum (MIS 15-11) (Guo et al., 1998, 2009), which included some pronounced interglacial events in Western Europe, e.g. MIS 11, and 13. Hominins at this time would have experienced a warmer and more humid climate in this area than during periods of substantial loess deposition. 5. Comparison with Qiaojiayao site
The artifact raw materials are vein quartz and quartzite although most of the artifacts (>92%) are made of vein quartz. The Paleolithic assemblage at Liuwan localities 2 and 3 is composed of small stone tools (<6 cm) manufactured from vein quartz, quartzite cobbles and pebbles with evidence of hard hammer direct percussion or bipolar flaking techniques. Their form is similar to the small tools of north China. The Liuwan localities 2 and 3 lithic industry is characterized by random knapping that lacks retouch and the shaping is opportunistic. It appears that the assemblage is a core and flake lithic technology. The main characteristics of the Liuwan localities 2 and 3 assemblage are: 1) tools are characterized by scrapers, points and stone hammers; 2) scrapers are the dominant retouched tools, but only 2e4 retouched scars can be indentified on each lithic artifact; 3) all cores have unprepared platforms. The flake scars on each core are random and irregular, with no more than 5 per core; bipolar flaking is used commonly in vein quartz cores. Importantly, the excavated lithic assemblage of Liuwan localities 2 and 3 is different from the surface finds and previous collections in Liuwan locality 1. These are dominated by large cutting tools, such as, picks and handaxes (Wang et al., 2005a, b, 2008; Lu et al., 2007, 2011a; Shaanxi Provincial Institute of Archaeology et al., 2007).
A number of Paleolithic sites have been found along the South Luo River, but only a few, such as the Longyadong Cave site (Wang and Huang, 2001; Sun et al., 2013) and Qiaojiayao site (Lu et al., 2011b) have been systematically studied and dated. Though the Longyadong Cave is only 4 km away from Liuwan site, it is much younger than the Liuwan site (Sun et al., 2013). Qiaojiayao is one of the oldest Paleolithic sites in the area with an approximate age 600 ka (Lu et al., 2011b) and is similar to the Liuwan site. Both have the S5 soil unit and both sites lay on the second terrace composed of a thick loessepaleosol deposit. The Qiaojiayao assemblage is dominated by small vein quartz artifacts produced by direct hard hammer percussion or bipolar flaking, similar to the Liuwan artifacts. The Qiaojiayao lithic assemblage is composed of 880 artifacts, with 18 cores, 132 flakes, 713 angular fragments, 1 hammer stone, 5 manuports and 11 retouched tools. These retouched tools are composed of 3 choppers, 6 scrapers, 1 point, and 1 burin. The retouched tools are made on flakes with a maximum of 2e4 retouched scars. These simple and rudimentary artifacts consist of scrapers and points and represent an early Paleolithic industry. Raw materials include vein quartz, a variety of quartzite, greywacke, and granites. The vein quartz and
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Fig. 4. Representative flakes, stone tools, and cores from artifact layer 1 (Fig. 4A) in Liuwan locality 2 and artifact layer 2 (Fig. 4B) in Liuwan locality 3. Artifact layer 1 in locality 2: flakes (a, b, and c), scrapers (d, e, and f), cores (g and h). Artifact layer 2 in locality 3: flakes (i and j), points (k and l), scrapers (m, n, and o), cores (p and q).
quartzite comprise more than 99% of the assemblage. A technological continuum is evident between the Liuwan and Qiaojiayao sites based on the similarity of raw materials, tools, and flaking debris. The other common feature of the two sites is the changing use of raw material over time. In the early sequences of Qiaojiayao from about 1810 cm to 1780 cm all the artifact raw material is vein quartz. Then quartzite usage begins at 1780 cm, with vein quartz (81.2%) and quartzite (17.8%) artifacts appearing together from 1780 cm to 1740 cm. Greywacke and granites also are found in these levels but in very low proportions (1%) (Fig. 6). The Liuwan site shows similar raw material changes identified in artifact layer 1 and artifact layer 2 (Fig. 6). Within artifact layer 1 at both locality 1 and locality 2, all the excavated artifacts are vein quartz artifacts (100%). In artifact layer 2 at locality 3, the
percentage of vein quartz artifacts is 88.8%, and the percentage of quartzite artifacts is 11.2% (Fig. 6). This evidence may indicate that a regional change occurred in the procurement of raw materials for lithic artifacts beginning about 600 ka, with the addition cobbles for artifacts made of fine grained quartzite to a technology based on vein quartz. 6. Conclusions The Liuwan stone tool assemblages consist of simple and basic scrapers, points, and stone hammers dating to the middle Paleolithic. Based on the Ages of the loessepaleosol sequence at Liuwan locality 1 and the comparison of the magnetic susceptibility, the chronology of locality 2 were suggested as S1, L2, S2, L3, combined S3eS4, L5, S5 SS1, S5 LL2, S5 SS2, S5 LL3, and S5 SS3, and the
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Fig. 5. Magnetostratigraphy, pedostratigraphy, and magnetic susceptibility of the loessepaleosol sequence in Liuwan site. Magnetic susceptibility correlating among Liuwan localities 1, 2, and 3, and Luochuan section.
Fig. 6. Comparison of artifacts in raw materials comprising at Liuwan and Qiaojiayao sites.
chronology of locality 2 were suggested as combined S3eS4, L5, S5 SS1, S5 LL2, S5 SS2, S5 LL3, and S5 SS3 in sequence. The ages of artifact layer 1 in S5 SS3 and layer 2 in S5SS2 are 681e625 ka and 568e575 ka respectively. This paper suggests a probable change in raw materials exploitation from vein quartz in the artifact layer 1 to a mixed vein quartz and quartzite in the artifact layer 2. It may be that as these early hominids became increasingly familiar with the Luonan Basin’s environment about 600 ka, a wider use of raw material was made and incorporated into their technology. Acknowledgements We thank Profs. Xing Gao, Wei Wang, Xiaoqiang Li, Jef Vandenberghe for valuable discussions; we are in debt to Mr. Chuanbin Yang for his help in the field and laboratory works. This Research is supported by the National Natural Science Foundation of China (41202127 and 41072122), the Priority Academic Program
Development of Jiangsu Higher Education Institutions, and the Fundamental Research Funds for the Central Universities (1082020904), the CAS Strategic Priority Research Program (No. XDA05130201), and the 100 Talents Program of Chinese Academy of Sciences (KZCX2-YW-BR-24).
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Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China Xuefeng Sun a, *, Huayu Lu a, Shejiang Wang b, Richard Cosgrove c, Wenchao Zhang a, Kaifeng Yu a, Haixin Zhuo a a School of Geographic and Oceanographic Sciences, MOE Key Lab of Coast and Island Development, Nanjing University, Hankou Road 22, 210093 Nanjing, China b Joint Laboratory of Human Evolution and Archaeometry, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China c Archaeology Program, School of Historical and European Studies, La Trobe University, Victoria 3086, Australia
a r t i c l e i n f o
a b s t r a c t
Article history: Available online xxx
The Luonan Basin contains thousands of stone artifact scatters located in the upper drainage of South Luo River, central China. Despite many years of survey, the age of these Paleolithic artifacts remained uncertain. In 2007, our team established for the first time a chronological framework for the natural loess deposit at locality 1, at the site of Liuwan. Here we report on two in situ artifact assemblages buried in loess deposit which were excavated at Liuwan localities 2 and 3 in 2009. The characteristics of these two Paleolithic assemblages are similar: the stone artifacts are small, and include stone hammers, cores, flakes, chunks, debris, and a small number of retouched tools, represented primarily by scrapers and points. We dated the loessepaleosol sequences at the two new localities, established chronology on the basis of stratigraphic analysis and comparison of magnetic susceptibility profiles between localities 1, 2, and 3, and the typical loessepaleosol time series. Our results suggest that the artifact bearing layer 2 at locality 3 is in the S5 SS2 paleosol unit, dated to between 575 and 568 ka; the artifact bearing layer 1 at localities 2 and 3 is in the soil unit S5 SS3 dated to between 625 and 581 ka. This result suggests that hominin occupation of the Luonan Basin occurred between 625e581 ka and 575e568 ka, there is a probable change in raw materials exploitation from vein quartz in the artifact layer 1 to a mixed vein quartz and quartzite in the artifact layer 2. The Liuwan site is chronologically similar to the Qiaojiayao site in the middle of South Luo River, and indicates that the hominins ranged widely in the Qinling Mountains during the Middle Pleistocene. Ó 2014 Elsevier Ltd and INQUA. All rights reserved.
Keywords: Middle Pleistocene Luonan Basin Loess Magnetic susceptibility Stone artifacts
1. Introduction Research has shown that the Luonan Basin is an important locality for understanding middle Pleistocene hominid occupation and settlement (Wang, 1986; Wang and Huang, 2001; Wang et al., 2004, 2005a, b, 2011; Lu et al., 2007, 2011a; Sun et al., 2013.), but the age of Luonan Paleolithic assemblages are still unclear. The nearby region contains a number of important early and middle Pleistocene archaeological deposits such as those from Lantian (Jia et al., 1966; An and Ho, 1989), Dali (Wang et al., 1979; Xiao et al., 2002; Yin et al., 2011), and Xihoudu sites (Zhu et al., 2003) (Fig. 1). Since the 1980s, investigations in the Luonan Basin have
* Corresponding author. E-mail address: [email protected] (X. Sun).
focused on the analysis of stone artifacts and their potential age but this has been hampered by the lack of suitable datable contexts (Wang, 1986; Xue, 1987; Wang et al., 2005a, b, 2008; Shaanxi Provincial Institute of Archaeology et al., 2007). In the most comprehensive investigation by Wang et al. (2004), the lithic artifacts excavated from Longyadong Cave have been the only ones systematically studied (Shaanxi Provincial Institute of Archaeology and Museum of Luonan County, 2008; Sun et al., 2013). The Luonan Basin is an intermountain depression with an elevation of 993 m, and is located in the upper drainage of South Luo River, eastern Qinling Mountains, central China (Fig. 1). It is regarded as the physical boundary between southern and northern China. The basin has an annual precipitation of 706 mm and an average annual temperature of 11.0 C, and a mosaic of grass, reforestation, and endemic plant communities covers the area. Loess sediment containing distinct loessepaleosol alternations was
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Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Fig. 1. Location of Liuwan archaeological site in Luonan Basin, upper South Luo River, central China and the related archaeological sites in adjacent regions.
deposited on terraces of the South Luo River in the Luonan Basin with thicknesses ranging from 1 to 25 m (Lu et al., 2007, 2012; Zhang et al., 2012). Surface scatters of Paleolithic artifacts are found on various landforms across this basin and good examples of in situ lithic artifacts occur at the Liuwan and Shangbaichuan sites (Lu et al., 2007, 2011a). The Liuwan site is situated on the second river terrace (Fig. 2), on the east bank of Maping River that flows into the South Luo River, 6 km north of the town of Luonan (Fig. 1). The Shangbaichuan site is also located on the second terrace of the Shimen River that flows into the South Luo River, 10 km south of the town of Luonan. The thick loessepaleosol deposit covers a series of fluvial sands, pebbles, and cobbles, which derived from the paleoriver channel. Excavation by local brick-makers has exposed a thick section of well-preserved loess and this has revealed many stone artifacts that were collected. At both sites, samples for optically stimulated luminescence (OSL) dating, magnetic susceptibility and paleomagnetic analyses were collected that established a timescale for these two loessepaleosol sequences (Lu et al., 2007, 2011a). To further refine the chronology, we conducted a detailed geological and archaeological survey at the Liuwan site in the summer of 2009, identifying layers containing in situ stone artifacts
in newly exposed loess sections (Fig. 3a, b, c). These sections are designated Liuwan localities 2 and 3. Two small (100 200 cm) test trenches (A and B) were dug at localities 2 and 3 where a total of 76 artifacts are excavated from a 5 cm thick horizon in trench A and 140 artifacts are unearthed in trench B, respectively. Artifact layer 1 lies w160 cm above layer 2 (Fig. 3b). Locality 1 is about 60 m southeast of locality 2, and locality 2 is about 40 m southeast of locality 3. The discovery and dating of these two artifact layers at Liuwan site should be meaningful for better understanding the age of hominid evolution in Luonan Basin.
2. Sampling, measurement, and stratigraphic analyses At Liuwan localities 2 and 3, samples were taken for magnetic susceptibility at an interval of 5 cm, yielding 270 bulk samples; fifty northerly-aligned cubic samples (2 2 2 cm3) were taken from locality 2 and locality 3 for paleomagnetic stratigraphic analysis. A Bartington MS-2 magnetic susceptibility meter was used to assess the magnetic susceptibility, and the paleomagnetic measurement was carried out using the 2G superconductor magnetometer at Nanjing University.
Fig. 2. Section of the Maping River terraces in which the artifact localities 1, 2 and 3 are located. The position of artifact layer 1 and 2 within the loessepaleosol section are indicated.
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Fig. 3. (a) Loessepaleosol section in locality 1; (b) The test excavation trench B in locality 3. L5 is clearly identified; (c) in situ artifacts discovered in the newly exposed loess section in locality 3.
For the magnetostratigraphic analysis, inclinations of all of the samples from localities 2 and 3 are positive, demonstrating that the loess was deposited in the Brunhes positive magnetic chron (N1) (Fig. 5), indicating that the loess deposits are younger than 0.78 Ma (Cande and Kent, 1995). These sediments were formed in the middle to late Pleistocene, chronologically similar to that of locality 1. The important point for this study is that the loessepaleosol stratigraphy in this area is uniform. Pedostratigraphic observation shows that L5 (the 5th loess unit in the typical Chinese loess sequence) is more prominent than the others and it is easily recognizable (Fig. 3a and 3b). At locality 2, the loess section is 8.5 m thick with five loess units and six paleosol layers. Based on the magnetic susceptibility variation between localities 1 and 2 and the field observations at locality 2, the loessepaleosol deposit here is identified as S1, L2, S2, L3, combined S3eS4, L5, S5 SS1 (SS ¼ sub soil), S5 LL2 (LL ¼ sub loess), S5 SS2, S5 LL3 and S5 SS3, respectively (Fig. 5). By comparing the magnetic susceptibility, the loess stratigraphy at these two localities appears identical. At locality 3 the loess deposit is only 5 m thick and three loess units and four paleosol complexes can be identified. Comparison of magnetic susceptibility and using L5 layer as a prominent marker, we conclude that the loessepaleosol sequence in locality 3 is similar to locality 2, with a combined S3eS4, L5, S5 SS1, S5 LL2, S5 SS2, S5 LL3, and S5 SS3 sequence (Fig. 5). Unfortunately the upper part of the loess section in locality 3 was eroded or disturbed. There is a distinct shift in the magnetic susceptibility below the S5SS1 soil unit in locality 1, 2 and 3. The magnetic susceptibility varies greatly above the S5SS1 soil, but below it is
relatively stable and consistent. This is different from the magnetic susceptibility recorded in the loessepaleosol sequence of central Chinese Loess Plateau (Fig. 5). Though below S5 SS1 the magnetic susceptibility is stable, but two close paleosol complexes were distinguished. So we deduced they are S5 SS2 and S5 SS3. For no negative paleomagnetic data found, the last paleosol at the bottom maybe S6 or S7. The reason for the abrupt shift may be that the magnetic susceptibility varies according to different temperature-moisture levels since ferromagnetic minerals will be destroyed under high moisture (waterlogged), pedogenic conditions (Zhao et al., 2008; Ao, 2010; Ao et al., 2010; Lu et al., 2011b; Sun et al., 2012). However, field observations of the paleosol units below the S5SS1 show the soil was clear and well developed suggesting that the magnetic susceptibility can still identify loess and paleosol units. 3. Paleolithic assemblages In trench A of Liuwan locality 2, artifact layer 1 is between 755 and 760 cm in depth (Fig. 6) and yielded 76 artifacts. It is comprised of scrapers, flakes, cores, debris, and chunks (Table 2 and Fig. 4a). In trench B at Liuwan locality 3, artifact layer 2 is between 305 and 310 cm deep from which 107 artifacts were excavated made up of scrapers, points, stone hammers, flakes, cores, debris, and chunks (Table 2 and Fig. 4b). Artifact layer 1 is located at a depth of 445e 450 cm (Fig. 6) and contains 33 artifacts including scrapers, points, stone hammers, flakes, debris, and chunks (Table 2). Paleolithic assemblages from Liuwan locality 2 and 3 are similar technologically (Table 2 and Fig. 4a, 4b).
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Table 1 Ages of the loessepaleosol sequence at Liuwan locality 1 (reference to Heslop et al., 2000). Stratigraphy
Depth (m)
Age (ka)
Soil L1 S1 L2 S2 L3 S3 & S4 L5 S5SS1 S5SS2 S5SS3 L6? S6?
0e0.50 0.50e1.20 1.20e2.30 2.30e3.05 3.05e3.55 3.55e4.05 4.05e5.50 5.50e6.00 6.00e8.20 8.20e9.40 9.40e10.10 10.10e11.80 11.80e12.50
e 10e71 79e129 129e196 196e250 250e290 290e417 417e503 503e556 568e575 581e625 e e
Table 2 Lithic artifact assemblages of two culture layers at Liuwan localities 2 and 3. Type Trench A e artifact layer 1 Scrapers Flakes Cores Debris Chunks Total Trench B e artifact layer 2 Scraper Point Stone hammer Flakes Cores Debris Chunks Total Trench B e artifact layer 1 Scraper Point Stone hammer Flakes Debris Chunks Total
Quantity
%
3 5 4 9 55 76
3.95% 6.58% 5.26% 11.84% 72.37% 100.00%
5 4 1 12 3 47 35 107
4.67% 3.74% 0.94% 11.21% 2.80% 43.93% 32.71% 100.00%
2 1 1 4 6 19 33
6.06% 3.03% 3.03% 12.12% 18.18% 57.58% 100.0%
4. Ages of Liuwan stone artifacts The magnetic susceptibility values of loessepaleosol sequences are high in soil and, low in loess units (Heller and Liu, 1984; Liu, 1985). These values are regarded as a good proxy of prevailing paleoclimatic conditions (Liu and Ding, 1998). The chronological sequence for the typical loess deposit of the Quaternary has been firmly established (Lu et al., 1999, 2004). These can be used to constrain the ages of the other loess deposits where they occur across north China. Magnetic susceptibility serves to distinguish soil and loess units and provides a clear record of climatic changes between the warmewet and coldedry that was dominated by Asian monsoon circulations in the Luonan Basin (Lu et al., 2007, 2011a). Therefore, we can compare the newly obtained magnetic susceptibility sequence of Liuwan sites with the independently controlled loessepaleosol time series to obtain ages for these new sequences that provides a robust chronological framework. At Liuwan locality 1 the loess section is 13 m thick with eight loess units and eight paleosol complexes. On the basis of four OSL ages (E. 146.6 12.3 ka, F. 137.0 13.4 ka, G. 151.6 4.9 ka, and H. 202.2 6.9 ka) (Fig. 5), the first and second paleosol units correspond to the S1 paleosol in central Chinese Loess Plateau, with an age 79e129 ka. The third paleosol unit correlates to the S2 soil that has an age of 196e250 ka while the fourth paleosol unit of S3 and S4 complex has an age of about 290e417 ka. The fifth, sixth, and seventh paleosol units were S5 SS1 (503e556 ka), S5 SS2 (568e 575 ka), and S5 SS3 (581e625 ka) soils, respectively (Table 1). On the basis of the magnetic susceptibility results and field observations, there is a clear correlation between the localities 1, 2, and 3. The oldest artifact layer in locality 2 and 3 is from the same layer and dates to the same time. Correlations with the Luochuan loessepaleosol sequence suggest that the paleosol containing the artifacts in layer 1 is within the S5SS3 soil, with a corresponding age of between 581 and 625 ka. The paleosol unit containing artifact layer 2 is located in the S5 SS2 soil dated to between 568 and 575 ka (Lu et al., 1999, 2004) (Fig. 5). As the S5 soil was formed during the Quaternary climatic optimum (MIS 15-11) (Guo et al., 1998, 2009), which included some pronounced interglacial events in Western Europe, e.g. MIS 11, and 13. Hominins at this time would have experienced a warmer and more humid climate in this area than during periods of substantial loess deposition. 5. Comparison with Qiaojiayao site
The artifact raw materials are vein quartz and quartzite although most of the artifacts (>92%) are made of vein quartz. The Paleolithic assemblage at Liuwan localities 2 and 3 is composed of small stone tools (<6 cm) manufactured from vein quartz, quartzite cobbles and pebbles with evidence of hard hammer direct percussion or bipolar flaking techniques. Their form is similar to the small tools of north China. The Liuwan localities 2 and 3 lithic industry is characterized by random knapping that lacks retouch and the shaping is opportunistic. It appears that the assemblage is a core and flake lithic technology. The main characteristics of the Liuwan localities 2 and 3 assemblage are: 1) tools are characterized by scrapers, points and stone hammers; 2) scrapers are the dominant retouched tools, but only 2e4 retouched scars can be indentified on each lithic artifact; 3) all cores have unprepared platforms. The flake scars on each core are random and irregular, with no more than 5 per core; bipolar flaking is used commonly in vein quartz cores. Importantly, the excavated lithic assemblage of Liuwan localities 2 and 3 is different from the surface finds and previous collections in Liuwan locality 1. These are dominated by large cutting tools, such as, picks and handaxes (Wang et al., 2005a, b, 2008; Lu et al., 2007, 2011a; Shaanxi Provincial Institute of Archaeology et al., 2007).
A number of Paleolithic sites have been found along the South Luo River, but only a few, such as the Longyadong Cave site (Wang and Huang, 2001; Sun et al., 2013) and Qiaojiayao site (Lu et al., 2011b) have been systematically studied and dated. Though the Longyadong Cave is only 4 km away from Liuwan site, it is much younger than the Liuwan site (Sun et al., 2013). Qiaojiayao is one of the oldest Paleolithic sites in the area with an approximate age 600 ka (Lu et al., 2011b) and is similar to the Liuwan site. Both have the S5 soil unit and both sites lay on the second terrace composed of a thick loessepaleosol deposit. The Qiaojiayao assemblage is dominated by small vein quartz artifacts produced by direct hard hammer percussion or bipolar flaking, similar to the Liuwan artifacts. The Qiaojiayao lithic assemblage is composed of 880 artifacts, with 18 cores, 132 flakes, 713 angular fragments, 1 hammer stone, 5 manuports and 11 retouched tools. These retouched tools are composed of 3 choppers, 6 scrapers, 1 point, and 1 burin. The retouched tools are made on flakes with a maximum of 2e4 retouched scars. These simple and rudimentary artifacts consist of scrapers and points and represent an early Paleolithic industry. Raw materials include vein quartz, a variety of quartzite, greywacke, and granites. The vein quartz and
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Fig. 4. Representative flakes, stone tools, and cores from artifact layer 1 (Fig. 4A) in Liuwan locality 2 and artifact layer 2 (Fig. 4B) in Liuwan locality 3. Artifact layer 1 in locality 2: flakes (a, b, and c), scrapers (d, e, and f), cores (g and h). Artifact layer 2 in locality 3: flakes (i and j), points (k and l), scrapers (m, n, and o), cores (p and q).
quartzite comprise more than 99% of the assemblage. A technological continuum is evident between the Liuwan and Qiaojiayao sites based on the similarity of raw materials, tools, and flaking debris. The other common feature of the two sites is the changing use of raw material over time. In the early sequences of Qiaojiayao from about 1810 cm to 1780 cm all the artifact raw material is vein quartz. Then quartzite usage begins at 1780 cm, with vein quartz (81.2%) and quartzite (17.8%) artifacts appearing together from 1780 cm to 1740 cm. Greywacke and granites also are found in these levels but in very low proportions (1%) (Fig. 6). The Liuwan site shows similar raw material changes identified in artifact layer 1 and artifact layer 2 (Fig. 6). Within artifact layer 1 at both locality 1 and locality 2, all the excavated artifacts are vein quartz artifacts (100%). In artifact layer 2 at locality 3, the
percentage of vein quartz artifacts is 88.8%, and the percentage of quartzite artifacts is 11.2% (Fig. 6). This evidence may indicate that a regional change occurred in the procurement of raw materials for lithic artifacts beginning about 600 ka, with the addition cobbles for artifacts made of fine grained quartzite to a technology based on vein quartz. 6. Conclusions The Liuwan stone tool assemblages consist of simple and basic scrapers, points, and stone hammers dating to the middle Paleolithic. Based on the Ages of the loessepaleosol sequence at Liuwan locality 1 and the comparison of the magnetic susceptibility, the chronology of locality 2 were suggested as S1, L2, S2, L3, combined S3eS4, L5, S5 SS1, S5 LL2, S5 SS2, S5 LL3, and S5 SS3, and the
Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Fig. 5. Magnetostratigraphy, pedostratigraphy, and magnetic susceptibility of the loessepaleosol sequence in Liuwan site. Magnetic susceptibility correlating among Liuwan localities 1, 2, and 3, and Luochuan section.
Fig. 6. Comparison of artifacts in raw materials comprising at Liuwan and Qiaojiayao sites.
chronology of locality 2 were suggested as combined S3eS4, L5, S5 SS1, S5 LL2, S5 SS2, S5 LL3, and S5 SS3 in sequence. The ages of artifact layer 1 in S5 SS3 and layer 2 in S5SS2 are 681e625 ka and 568e575 ka respectively. This paper suggests a probable change in raw materials exploitation from vein quartz in the artifact layer 1 to a mixed vein quartz and quartzite in the artifact layer 2. It may be that as these early hominids became increasingly familiar with the Luonan Basin’s environment about 600 ka, a wider use of raw material was made and incorporated into their technology. Acknowledgements We thank Profs. Xing Gao, Wei Wang, Xiaoqiang Li, Jef Vandenberghe for valuable discussions; we are in debt to Mr. Chuanbin Yang for his help in the field and laboratory works. This Research is supported by the National Natural Science Foundation of China (41202127 and 41072122), the Priority Academic Program
Development of Jiangsu Higher Education Institutions, and the Fundamental Research Funds for the Central Universities (1082020904), the CAS Strategic Priority Research Program (No. XDA05130201), and the 100 Talents Program of Chinese Academy of Sciences (KZCX2-YW-BR-24).
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Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061
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Please cite this article in press as: Sun, X., et al., Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.04.061