ACTA ANTHROPOLOGICA SINICA

Size: px

Start display at page:

Download "ACTA ANTHROPOLOGICA SINICA"

Richard Lloyd
5 years ago
Views:

1 ACTA ANTHROPOLOGICA SINICA Vol128,No13 Aug.,2009 1, 1, 1, 2, 3 (11, ; 21, ; 31, ) :, IRSL BLSL , , : ; ; ; : P533 : A : (2009) , 9000,,, ;, ;,,,, 1000,,,,,, 14 C,,, (Md, ) 166, (Ma) ,80 ; ; 14 C [1 ] ; ESR [2 ], [3 ], : ; : : (No ) : (19432),,, E2mail nara2edu. ac. jp com

2 3 : 277,, (Optically Stimulated Luminescence, OSL) OSL Simon Fraser D.J. Huntly (51415nm ) [4 ], ( Infrared Stimulated Luminescence, IRSL) G1H tt [5 ], 51415nm, [6 ], OSL, ( 1), 6 2 6, 2, 2 :1) ;2) ;3),, ;4), 5cm ;5),, ;6),,, OSL, 1 Fig11 Locations of Youfang site, Hutouliang site and Xujiayao site in the Nihewan Basin, China

3 ( 1 lx),, [7 ] ( 1 8 m) 10 % H 2 O 2 16, HCl 115,,20 % H 2 SiF TLΠOSL NRL2992OSTL TLΠOSL [8 ] NRL2992OSTL, 500 ; TLΠOSL ( TL) (OSL), 32 OSL, 32 (470nm) ( ), 32 (890nm), - 20 (PMT) (R1140P, ) 250mm 380nm (FWHM), 350mm 600nm, 350mm 470nm 213 (P) NRL2992OSTL, ( MAAD), 60 Co IRSL :160,60, [9 ] MAAD, ( BLSL ),:220 60, ( ) 10 %0115GyΠka, U Th 40 K TL (CaSO 4 :Tm powder ; Matsushita ) [10 ], ( TLD) (CaSO 4 : Tm,Matsushita UD2110S),3 3 IRSL BLSL 1 IRSL ka BP( ) 69 8ka BP ( ) TL, TL ( > 100klx) 4 6, 13ka 14ka BP 15 17ka BP, IRSL BLSL

4 3 : IRSL BLSL Tab11 Result of measurements, paleodoses, annual doses and luminescence ages by IRSL and BLSL methods. (Site) (Stratigraphic position of sample) (Paleodose) ( Gy) (Annual dose) ( GyΠka) (Luminescence age) (ka) IRSLΠBLSL ( Hutouliang Loc165039) ( Youfang) (Xujiayao Loc174093) 6 (Upper portion of layer 6) 6 (Lower portion of layer 6) (Upper layer of the artifact horizon) (Lower layer of the artifact horizon) (Upper layer of the artifact horizon) (The artifact Horizon) IRSL IRSL IRSL 14 4 BLSL IRSL 16 3 BLSL IRSL IRSL :,,IRSL 2 6 IRSL Fig12 Experimental results for the lower portion of 6 layer at Hutouliang site. IRSL decay curves (left) and growth curves (right) for the equivalent dose (upper) and for the supralinearity correction (lower) a, ;b, ; c, ;d,

5 IRSL ( 2) 14 C 1110ka 1116ka BP [11 ] 104ka 125ka BP [12 ],,,,,,,,,,, OSL, :, Xing Wei ( ) Susan Keates, : [ 1 ]. [A]. : [ C]. :,2003, [ 2 ],. ESR [J ]., 2009, 29 (1) : [ 3 ] Wei Qi. On magnetostratigraphic dating of Palaeolithic sites in the Nihewan basin, China[A]. 18TH IPPA Congress Manila[ C]. 2006, [ 4 ] Huntly DJ, Godfrey2Smith DI,Thewalt MLW. Optical dating of sediments[j ]. Nature , [ 5 ] Hutt G, Jaek I,Tchonka J. Optical dating : K2feldspars optical response stimulation spectra [J ]. Quat Sci Rev , [ 6 ],. [J ]., 2004, 23 ( ) : [ 7 ] Zimmerman DW. Thermoluminescence from fine grains from ancient pottery[j ]. Archaeometry, 1967,10 : [ 8 ] Nagatomo T,Shitaoka Y. Development of low temperature OSL apparatus and its application to dating [J ]. Advances in ESR Applications, 2000,16 : 45 (in Japanese). [ 9 ] Shitaoka Y, Nagatomo T. Studies on OSL of quartz and feldspar for dating of sediments[j ]. Radioisotope, 2001,50 (9) : (in Japanese with English abstract). [10 ] Ichikawa Y, Hagihara N,Nagatomo T. Dating of Pyroclastic Flow Deposits by means of the Quartz Inclusion Method[J ]. PACT, 1982, 6 : [11 ]. [A]. : [ C]. :, 1991, [12 ],,. [J ]., 1984, 3 (3) :

6 3 : 281 OSL Dating of the Strata at Paleolithic Sites in the Nihe wan Basin, China Tsuneto Nagatomo 1, Yorinao Shitaoka 1, Hisae Namioka 1, Ma sato shi Sagawa 2, WEI Qi 3 (1. Nara University of Education, Takabatake2cho, Nara , Japan ; 2. Tohoku Gakuin University, Tsuchitoi 12321, Aoba2ku, Sendai , Japan ; 3. Institute of Vertebrate Paleontology & Paleoanthropology, Chinese Academy of Sciences P. O. Box 643, Beijing , China) 1 Introduction Many Paleolithic sites such as Hutouliang, Xujiayao, Donggutuo, Xiaochangliang, etc. in the Nihewan Basin, China have been discovered and yielded important information of the prehistoric archaeology and anthropology in East Asia. The Nihewan Beds are composed of alternate layers of red clay sediments and deposits of loess. The Sanggang River eroded these layers, and the eroded bluffs and the taluses created complicated landforms, resulting in difficulties in determining the ages of the strata and the Paleolithic sites. The ages of the Paleolithic sites in the Nihewan Basin have been inferred mainly from the stratigraphic studies, 14 C dating, and uranium series dating. Paleomagnetism has also been applied to some paleolithic sites. Based on these data, the artifacts and mammal bone fossils found at these sites are considered to be from Lower Pleistocene to Upper Pleistocene. For instance, the ages of Md ( Goudi, Majuangou), Xiaochangliang, and Ma ( Banshan) sites were estimated by paleomagnetism to be 1166Ma BP, 1136Ma BP, and 1132Ma BP respectively, Xujiayao site was estimated by uranium series to be kaBP, Shenquansi site was estimated by 14 C dating to be BP, and Dongpo site was estimated by ESR dating to be ka BP. These estimated ages are of great scientific significance, but they might not be all accurate and conclusive. Much research is still needed to establish the geochronological framework of this region. To obtain supplemental chronological, it would be essential to analyze the ages of these paleolithic sites with various scientific techniques applicable to the deposits andπor relics. One such technique is optically stimulated luminescence (OSL) dating, which directly estimates the age of sediment by utilizing some minerals residing in it. OSL dating was first applied to sediments by Huntly et al. using an argon2ion laser (514152nm light). OSL dating can directly determine the age of loess and fluvial sediment by measuring the time period since their last exposure to sunlight. Infrared stimulated luminescence ( IRSL) dating, in which infrared light is used instead of nm light, was first performed by Hutt et al. using potassium feldspar samples. In China, results of IRSL dating were reported for Xarusgol (Sjara2osso2gol), a Paleolithic site in north China, but some details of the measurements are still unclear. In this article, we show the procedure and the results of OSL dating for sedimentary samples from

7 three Paleolithic sites in the Nihewan Basin, and compare our finding with result hitherto obtained by other dating techniques. 2 Measurements 211 Samples The six sedimentary samples were collected from three Paleolithic sites, namely Hutouliang, Youfang, and Xujiayao, in the Nihewan Basin ( Fig11). The samples of Hutouliang were collected from the upper and lower portions of the 6th layer. At Youfang site, samples were collected from the upper and lower layers of the artifact horizon. Two samples were also collected from the upper layer of the artifact horizon and the artifact horizon at Xujiayao site. All samples from strata had their top surfaces of about 5 cm removed in a dark condition with an opaque cloth, because the minerals in the surface layer had been bleached out by sunlight and would make the OSL dating inaccurate. The minerals in a collected sample were first roughly separated into fine and coarse grains in water, and then fine grain ( FG) minerals (about 1 8 microns) were obtained by the suspension technique in acetone. Subsequently, the FG minerals were treated with 10 % H 2 O 2 for 16 hours and 10 % HCl for 90 minutes to remove organic materials and carbonates. The FG minerals from both the upper and lower layers of Youfang site were divided into two groups, and one of them was treated with 20 % H 2 SiF 6 to get only fine quartz grains. than 1 lx. These sample preparation procedures were carried out in a dark room with dim red lighting lower 212 Automated TLΠOSL reader The measurements were taken with a TLΠOSL reader (NRL2992OSTL). The NRL2992OSTL reader has two assemblies of temperature2controlled sample holders, one being controlled from room temperature to 500 and the other being kept at by flowing liquid nitrogen. This TLΠOSL reader automatically measures the thermoluminescence ( TL) and OSL of up to 32 aliquots. For OSL measurements, an excitation system with 32 blue2light (470 nm) diodes (Nichia Chemical Industries Co., Ltd. ) was installed, which could be replaced with another system with 32 infrared (890 nm) diodes (Hamamatsu photonics Co., Ltd. ). The luminescence from a sample was directed to a PMT (R1140P, Hamamatsu photonics Co., Ltd. ) housed in a cooling unit ( - 20 ) through two condensing lenses and an optical filter set. An optical filter set with a transmission range of nm ( FWHM) was used for blue2light excitation, nm range was used for infrared2light excitation, and nm was used for TL measurements. 213 Estimation of paleodose The fine mineral samples were measured with the conventional multiple2aliquot additive dose (MAAD) protocol using the NRL2992OSTL reader. Additive doses were given with a calibrated 60 Co gamma2ray source for the measurement of equivalent doses ( ED). The IRSL measurements were made with a 1002second infrared light exposure at 60 after preheating of 160 for 60 seconds. Fine

8 3 : 283 quartz samples from Youfang site were also measured with the MAAD protocol but stimulated with the blue light LEDs ( to be referred to as BLSL hereafter). The measurements were made with a 1002 second blue light exposure at 120 after preheating of 220 for 60 seconds. The measurements for supralinearity correction were made with the samples annealed at 350 for 60 minutes. 214 Estimation of dose rate ( annual dose) The dose rate for a sample is the sum of the measurements of the alpha particles, and of the beta, gamma and cosmic rays. These components of the dose rate were evaluated from the concentrations of U, Th, 40 K measured using a gamma2ray spectrometer with a highly2pure Ge detector, assuming an alpha efficiency of 10 % and a cosmic2ray dose rate of 0115 GyΠka. Beta2ray dose rate of each sample was also measured by using TL dosimeter ( CaSO 4 : Tm powder ; Matsushita Co. Ltd. ) sandwiched between two disks made of the untreated sample grains. For the samples from Hutouliang site, gamma2 ray dose rate and cosmic2ray dose rate were estimated on site by using TLD capsules (CaSO 4 : Tm, Matsushita UD2110S) enclosed in a copper tube. The dose rates of beta rays for all samples and gamma rays for those from Hutouliang site obtained by different techniques were reasonably consistent with each other. 3 Results and discussion The paleodoses, annual doses and IRSL or BLSL ages for all the samples are listed in Table 1. IRSL ages obtained for three sites range from ka (the upper portion at Hutouliang site) to 69 8ka (the artifact horizon at Locality 74093, Xujiayao site). Tab11 The data of IRSL and BLSL ages of Paleolithic sites in Nihewan Basin Site Hutouliang (Loc165039) Youfang Xujiayao (Loc ) Stratigraphic position of sample Upper portion of layer 6 Lower portion of layer 6 Upper layer of the artifact horizon Lower layer of the artifact horizon Upper layer of the artifact horizon The artifact Horizon Paleodose ( Gy) Annual dose ( GyΠka) Luminescence age (ka) IRSLΠBLSL IRSL IRSL IRSL 14 4 BLSL IRSL 16 3 BLSL IRSL IRSL We attempted to measure the samples (fine multimineral samples and fine quartz samples) from Youfang site with the residual TL technique. Residual TL was estimated by exposing the samples to sunlight ( > 100klx) for 4 6hours. The results were 13 14ka and 15 17ka for the upper and lower layers of the artifact horizon, respectively. These results are in good agreement with the IRSL and BLSL measurements. The IRSL age of Hutouliang site is roughly consistent with the 14 C age, 1110 to 1116ka, reported

9 by Gai. The age of Xujiayao site had been estimated earlier with the uranium series dating method to be ka BP, which deviates from our result to some extent. In order to clarify the age of Xujiayao site, we need to examine the two sets of measurements in more details, for example, from which strata the samples were collected and how the experiments were carried out. The results in the present work should be further verified by the other dating techniques, and the inter2laboratory comparison of OSL dating is also desired. A steady accumulation of scientific data is essential for establishing a Pleistocene geochronological framework of the Nihewan Basin and the ages of Paleolothic sites in this region. Acknowledgements : This work was partially supported by a Grant in Aid for the Scientific Research from the Ministry of Education, Science and Culture, Japan (No ). Key words : OSL dating ; Prehistoric sites ; Nihewan Basin ; North China ,,,,,,, ( )

SCIENTIFIC DATING IN ARCHAEOLOGY

SCIENTIFIC DATING IN ARCHAEOLOGY Tsuneto Nagatomo 1. AGE DETERMINATION IN ARCHAEOLOGY Relative Age: stratigraphy, typology Absolute Chronology: historical data Age Determination by (natural) Scientific