- Email: [email protected]
Time range for accumulation of shell middens from Higashimyo (western Japan) and Kimhae (southern Korea) by AMS radiocarbon dating
Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
Contents lists available at SciVerse ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Time range for accumulation of shell middens from Higashimyo (western Japan) and Kimhae (southern Korea) by AMS radiocarbon dating Toshio Nakamura a,⇑, Akira Matsui b, Iwao Nishida c, Mitsuru Nakano c, Takayuki Omori d a
Center for Chronological Research, Nagoya University, Chikusa, Nagoya 464-8602, Japan National Research Institute for Cultural Properties, Nara, Nijyo-cho, Nara 630-8577, Japan c The Saga-City Board of Education, Sakae-machi, Saga 840-8501, Japan d University Museum, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan b
a r t i c l e
i n f o
Article history: Received 31 July 2011 Received in revised form 29 August 2012 Available online 25 October 2012 Keywords: Shell midden Accumulation time Bayesian analysis 14 C age Higashimyo site Kimhae site
a b s t r a c t Numerous large and small shell middens have been reported throughout the world. An interesting question is when the huge and thick shell middens were formed, and how many years were required to build up the whole midden. Shell middens contain not only shell fragments but also organic substances such as bones, nuts, acorn, and plant residues, which are suitable substances with which to establish 14C chronology of the middens. We have conducted 14C dating on terrestrial and marine materials collected from two lowland shell middens, the Higashimyo site in Japan (the Earliest Jomon period) and the Kimhae site in Korea (the Proto-Three Kingdom period), to establish high precision 14C chronologies and determine the time required for shell accumulation. According to Bayesian analysis of 14C ages from terrestrial samples, accumulation of Midden No. 1 at Higashimyo (altitude from 1.1 to 2.3 m a.s.l., Dd = 1.2 m) started at around 8050–7950 cal BP and ended at 7950–7750 cal BP, lasting for ca. 100 cal yr, while accumulation of Midden No. 2 (altitude from 0.5 to 2.0 m a.s.l., Dd = 1.5 m) started at around 8050–7800 cal BP and ended at 7800–7650 cal BP, lasting for ca. 200 cal yr. Thus the Midden No. 1 was abandoned a bit earlier than Midden No. 2, but the time range for sediment accumulation overlaps each other. Accumulation at the Kimhae shell midden (altitude from 5 to 14 m a.s.l., Dd = 9 m) started at around the middle of the 1st C cal BC and ended at around the middle of the 3rd C cal AD, lasting for ca. 250 to 300 cal yr. Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction It is an archeologically interesting question when huge and thick shell middens were formed, and how long it took to build them up. Pottery fragments excavated from middens can be analyzed to estimate the age as well as their accumulation time on the basis of the typological evidence. However, since available pottery fragments are limited, the estimation of the age and the accumulation time can be less reliable than expected. Shell middens contain not only shell fragments but also organic substances such as bones, nuts, acorn, and plant residues, which are suitable substances to use to establish a 14C chronology of the midden. In this article, we focus on two shell middens: the Higashimyo shell midden in Saga prefecture, southeast of Japan, and the Kimhae shell midden, Kimhae city, south of Korea. The Higshimyo site is a wetland shell midden formed during the earliest Jomon period (10,000–6000 cal BP) [1]. The Higashimyo site is composed of six shell middens produced separately at the intertidal zone during the marine transgression in the Holocene ⇑ Corresponding author. Tel.: +81 52 789 3082; fax: +81 52 789 3092. E-mail address: [email protected] (T. Nakamura). 0168-583X/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nimb.2012.08.047
period after the final ice age, and was abandoned as the result of rising sea level. We have measured 14C ages of shell, nut, acorn, wood, and herbaceous-plant remains excavated from the shell middens in order to analyze and establish the accurate chronology of the site [2]. The Kimhae shell midden, formed in the Proto-Three Kingdom period (1st C BC to mid-4th C AD), consists of 9 m deep sediments from 14 m a.s.l. down to 5 m a.s.l., including numerous huge oyster shells and big clamshells (Meretrix lusoria), intercalated with clear charcoal layers or charcoal fragmental lumps [3]. Using several pairs of shell and charcoal material from the same horizon of the sediment, we analyzed the time range required for sediment accumulation. 2. Archeological sites 2.1. Higashimyo archeological site The Higashimyo archeological site consists of a dry residential area and six shell middens located in the huge Saga Plain, the largest plain in western Japan, at the northern part of Kyushu Island (Fig. 1) [1]. The Saga plain faces south onto the innermost part of
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
681
Fig. 1. Location of Higashimyo and Kimhae sites and layout of Nos. 1–6 middens at Higashimyo.
Ariake bay, a bay extending 20 km wide in the east–west and 60 km long in the south–north directions with relatively shallow water depths (ca. 20 m on average). The Higashimyo midden was formed on the coastline at an early stage of the maximum transgression period (8–6 ka cal BP) and sank by means of successive sea-level rise. The range of high and low tides is about 5 m at the innermost part of Ariake bay, so many storage pits were placed in the intertidal zone. Of greatest archeological interest is the fact that more than 750 baskets woven with twisted ropes made of thinly sliced wood were unearthed along with plenty of nuts and acorns preserved inside them. The woven wooden baskets excavated here are the oldest (ca. 7800–7900 cal BP) ones recorded in the earliest Jomon period. At the residential area on the dry high terrace (ca. 3 m a.s.l.), about 50 m east from Middens Nos. 1 and 2, fireplaces with many charred stones and a presumed burial containing more than five people have been unearthed [1]. A huge number of shell fragments were accumulated in the Higashimyo shell middens. Six shell middens were detected separately at the Higashimyo site, extending about 400 m in the south–north direction, and numbered 1 to 5 from south–north. Midden No. 6 is located in the southern most part of the site and was discovered last (Fig. 1). Lengths and areas of the shell middens were 30 and 300, 40 and 400, 20 and 200, 45 and 430, 15 and 40, and 55 m and 330 m2, for Middens No. 1 to No. 6, respectively.
Middens Nos. 1 and 2 were intensively excavated. In Midden No. 1, the thickness of the mound was ca. 1.2 m and the elevations of the lowermost and uppermost levels were 2.3 and 1.1 m a.s.l. For Midden No. 2, the respective values were 1.5 m, and 2.0 and 0.5 m a.s.l. We have collected shell fragments and terrestrial plant remains from the full layers, from the bottom to the top, of the two middens for 14C dating, in order to estimate the time required to accumulate the total volume of the middens. Four kinds of shell fragments were mainly collected at the site. They were Japanese corbicula (Corbicula japonica), cockles (Fegillarea granosa), jackknife clams or razor shell (Sinonovacula constricta), and oyster (Crassostrea gigas Crassostrea ariakesis). We normally used cockles for dating because of its potential strength against surface weathering. We also collected terrestrial plant remains consisting of twigs, wooden stakes, acorns, fragments of wooden sticks used to make up a basket, wooden twisted cords, wooden boards, etc., which were less likely to show ‘‘old wood’’ effect. 2.2. Kimhae Heohyeon-ni shellmidden The Kimhae Heohyeon-ni shell midden is located at Kimhae city along the lower Nakdong-gang river, on the alluvial plain formed by filling the paleo-Kimhae bay with deposits supplied by the Nakdong-gang river (Fig. 1) [3]. The midden was first excavated
682
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
Table 1 14 C ages and calibrated dates for plant remains collected from storage pits situated at four different horizons at Higashimyo. No.
Storage pit No.
Layer
Dated material
Upper horizon 1 SK2002
Uppermost
2
SK2002
Uppermost
3
SK2002
4
SK2001
Lower part of 5th layer East half of 2nd layer
Wooden stake (K22666) Wooden stake (K20011) Acorn (Quercus aliena) Acorn (Quercus aliena) Acorn (Quercus gilva) Woven basket (AM2250) Wood plate Acorn (Quercus gilva) Acorn (Quercus gilva) Woven basket
Middle horizon 5 SK2106
–
6
SK2106
–
7 8
SK2106 SK2095
– Southern half
9
SK2093
Southern half
10
SK2093
3rd layer
d13CPDB by AMS (‰)
Conventional 14C age (BP, ±1r)
Calibrated date.(OxCal4.1, possible age range in 1r error, probability)
Lab. Code No. (NUTA2-)
27.5 ± 1.0
6574 ± 26
7485–7434 cal BP (68.2%)
13661
30.6 ± 1.0
6567 ± 27
7481–7433 cal BP (68.2%)
13662
24.0 ± 1.0
6624 ± 36
13855
26.8 ± 1.0
6985 ± 33
7565–7532 cal BP (30.9%).7520–7480 cal BP (37.3%) 7920–7902 cal BP (10.3%).7861–7786 cal BP (57.9%)
26.6 ± 1.0
7029 ± 34
BP (34.9%).7878–7838 cal BP
13370
31.0 ± 1.0
7072 ± 33
BP (27.6%).7900–7864 cal BP
13372
29.7 ± 1.0 25.5 ± 1.0
7042 ± 36 7054 ± 39
BP (68.2%) BP (19.2%).7906–7850 cal BP
13363 13200
24.7 ± 1.0
6963 ± 34
7931–7890 cal (33.3%) 7950–7922 cal (40.6%) 7932–7848 cal 7937–7914 cal (49.0%) 7840–7740 cal
BP (68.2%)
13368
28.4 ± 1.0
6993 ± 33
7922–7900 cal BP (13.8%).7864–7790 cal BP (54.4%)
13536
13519
Middle to lower horizon 11 SK2138 East half of 4th layer 12 SK2138 – 13 SK2138 –
Acorn (Quercus aliena) Woven basket Rope made of plant
26.0 ± 1.0
6968 ± 40
7848–7735 cal BP (68.2%)
13203
30.9 ± 1.0 30.8 ± 1.0
6882 ± 39 7116 ± 37
13205 13359
14
–
Wooden plate
27.7 ± 1.0
7044 ± 33
7754–7670 cal BP (68.2%) 7976–7930 cal BP (56.3%).7892–7876 cal BP (11.9%) 7932–7850 cal BP (68.2%)
Acorn (Quercus aliena) Acorn (Quercus acutissima) Woven basket(Sapindaceae) Acorn (Quercus aliena) Acorn (Quercus acutissima) Woven basket
27.2 ± 1.0
7122 ± 33
13535
26.2 ± 1.0
7114 ± 32
30.5 ± 1.0
6945 ± 47
7979–7932 cal BP (63.3%).7888–7880 cal BP (4.9%) 7972–7932 cal BP (59.3%).7889–7878 cal BP (8.9%) 7830–7710 cal BP (68.2%)
30.3 ± 1.0
7111 ± 32
28.3 ± 1.0
7092 ± 34
30.2 ± 1.0
7008 ± 40
SK2138
Lower horizon 15 SK2006 16
SK2056
Northern part of 6, 7th layer 10th layer
17
SK2056
–
18
SK2143
–
19
SK2134
–
20
SK2134
–
in 1920 by Japanese archeologists. Following several successive excavations, a large-scale excavation survey by the Sanko Institute of Cultural Properties, Korea, was carried out at the site in 2005 [4]. Three trenches as deep as 9 m, at a height of 14 m down to 5 m a.s.l., were dug, and numerous shell fragments, intercalated with clear charcoal layers or charcoal fragmental lumps, were detected on the walls. A columnar sample of 30 30 cm2 from the top to the bottom of the trench was analyzed for shell assemblages, and a total of 5912 shells were recorded. The main components of the shells are: 36.6% Pacific oyster (Crassostrea gigas), 14.1% marsh snails (Semisulcospira bensoni), 8.8% horn shells (Batillaria multiformis), and 7.5% chowder clams (Meretrix lusoria) [4]. The sediment at the south wall of Trench No. 3 was classified stratigraphically into 113 layers. We collected pairs of chowder clamshell and charcoal material from 54 individual layers extending from top to bottom of the 9 m deep sediment to establish a high-precision 14C chronology and estimate the time range required for sediment accumulation. Large clamshell with a smooth surface is preferable for 14C dating rather than oyster shells which possess banded surface structures and could possibly be contaminated with foreign carbon.
7970–7930 cal BP (56.4%).7890–7877 cal BP (11.8%) 7960–7927 cal BP (41.2%).7896–7871 cal BP (27.0%) 7926–7896 cal BP (20.3%).7870–7794 cal BP (47.9%)
13362
11823 13212 11824 13371 13204
3. Experimental The nut and wood samples were processed with acid–alkali– acid treatments, rinsed with distilled water and dried. A part of the pre-treated sample was combusted to CO2 [5]. The shell samples were rinsed with diluted HCl (0.6 M) as well as distilled water in an ultrasonic cleaner, dried and powdered. The shell powder was decomposed with 95% H3PO4 in an evacuated bottle to produce CO2 [6]. CO2 was reduced to graphite on an iron catalyst under hydrogen atmosphere. All three carbon isotopes in graphite targets prepared from samples, NIST HOxII standard and 14C blank (oxalic acid synthesized from fossil fuel) were measured with an AMS system (HVEE model-4130) at Nagoya University [5]. The measured 14 12 C/ C and 13C/12C ratios were used to calculate the sample conventional 14C age. The obtained 14C ages were converted to calendar dates by using the calibration program OxCal 4.1 [7,8] and IntCal09 and Marine09 calibration data sets [9]. We have estimated the local marine reservoir correction, DR, in the present analysis, but the obtained DR values were less reliable with rather large errors. Since DR values were almost consistent with zero, we adopted DR = 0 for calibration of marine samples.
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
683
Fig. 2. Calibrated dates for plant remains collected from storage pits at Higashimyo.
4. Results and discussion 4.1. Higashimyo archeological site 4.1.1. Plant remains from storage pits Values of d13C, 14C age and calibrated ages are given in Table 1 for plant remains collected from storage pits situated at four different horizons: upper, middle, middle to lower and lower. Storage pits are located in the tidal range, because underwater storage of nuts is necessary for stable preservation, and also it is easy to approach the pit location whenever necessary. At the time of transgression, it would normally be expected that the calibrated ages become
younger, as the elevation of the storage pit increases. However, this tendency is not clear. This is because the tidal range (the vertical difference between the high tide and succeeding low tide) at the site is as large as 5 m. Since there was a huge area in which to make a new storage pit, a newer pit did not have to be located at a higher level. Except for the pit SK2002, all other storage pits were produced within two hundred years from 8000 to 7800 cal BP (Fig. 2). 4.1.2. 14C results for Middens Nos. 1 and 2 Tables 2 and 3 show values of d13C, 14C age and calibrated ages for marine shell and nut remains that were collected from different horizons in the 1F-belt and corresponding layers at No. 21 section
684
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
Table 2 14 C ages and calibrated dates for Cockles and nut remains collected from 1F belt and corresponding layers at No. 21 section of No. 1 shell midden at Higashimyo. No. Shell 1 2 3 4 5 6 7 8 9
Section No.
Horizon
samples collected from 1F 1F5–H1 Upper 1F5–H2 Upper 1F5–H3 Upper 1F24–H1 Middle 1F24–H2 Middle 1F24–H3 Middle 1F37–H1 Lower 1F37–H2 Lower 1F37–H3 Lower
Dated material belt of No. 1 shell midden Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell
d13CPDB by AMS (‰) 4.6 ± 1.0 5.8 ± 1.0 5.3 ± 1.0 5.3 ± 1.0 4.5 ± 1.0 4.4 ± 1.0 4.5 ± 1.0 5.7 ± 1.0 6.1 ± 1.0
Nut remains collected from No. 21 section(corresponding to 1F belt) 10 21–9–3 Upper Walnut (Juglans mandshurica 24.5 ± 1.0 var. sieboldiana) 11 21–57–1 Middle Walnut (Juglans mandshurica 24.9 ± 1.0 var. sieboldiana) 12 21–57–2 Middle Walnut (Juglans mandshurica 25.6 ± 1.0 var. sieboldiana) 13 21–94–1 Lower Acorn (Quercus gilva) 25.7 ± 1.0 14 21–94–2 Lower Acorn (Quercus gilva) 25.9 ± 1.0 15 21–94–3 Lower Acorn (Quercus gilva) 24.8 ± 1.0
Conventional 14C age (BP, ±1r)
Calibrated date (OxCal4.1,possible age range in 1r error, probability)
Lab. Code No. (NUTA2 )
7295 ± 34 7217 ± 35 7335 ± 34 7351 ± 34 7319 ± 34 7400 ± 34 7421 ± 34 7362 ± 35 7425 ± 34
7803–7704 cal 7724–7631 cal 7848–7748 cal 7866–7766 cal 7830–7733 cal 7916–7833 cal 7928–7848 cal 7885–7780 cal 7930–7851 cal
(68.2%) (68.2%) (68.2%) (68.2%) (68.2%) (68.2%) (68.2%) (68.2%) (68.2%)
13556 13557 13558 13559 13560 13563 13564 13565 13566
7071 ± 36
7951–7920 cal BP (27.3%).7902–7860 cal BP (40.9%) 7954–7922 cal BP (30.4%).7900–7864 cal BP (37.8%) 7973–7930 cal BP (54.1%).7892–7875 cal BP (14.1%) 7997–7937 cal BP (68.2%) 8008–7954 cal BP (68.2%) 8000–7950 cal BP (68.2%)
13849
7076 ± 36 7112 ± 37 7135 ± 37 7162 ± 39 7150 ± 37
BP BP BP BP BP BP BP BP BP
13850 13851 13852 13853 13854
Table 3 14 C ages and calibrated dates for shell and nut remains collected from different horizons at H belt of No 2. shell midden at Higashimyo. No.
Shell 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Section No.
Horizon
samples collected from H belt H3–H1 Uppermost H3–H2 Uppermost H3–H3 Uppermost H3–O1 Uppermost H3–O2 Uppermost H6–H1 Upper H6–H2 Upper H6–H3 Upper H15–H1 Middle H15–H2 Middle H15–H3 Middle H34–H1 Lowermost H34–H2 Lowermost H34–H3 Lowermost H34–O1 Lowermost H34–O2 Lowermost
Dated material
of No. 2 shell midden Cockles shell Cockles shell Cockles shell Oyster shell Oyster shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Oyster shell Oyster shell
Acorn and walnut remains collected from H belt of No. 2 shell midden 17 W–H6–b Upper Walnut (Juglans mandshurica var. sieboldiana) 18 A–H6–b Upper Acorn (Quercus gilva) 19 W–H7 Upper Walnut (Juglans mandshurica var. sieboldiana) 20 W–H14–1 middle Walnut (Juglans mandshurica var. sieboldiana) 21 W–H15 Middle Walnut (Juglans mandshurica var. sieboldiana) 22 W–H29–1 Lower Walnut (Juglans mandshurica var. sieboldiana) 23 W–H34–1 Lowermost Walnut (Juglans mandshurica var. sieboldiana) 24 W–H39–1 Lowermost Walnut (Juglans mandshurica var. sieboldiana)
d13CPDB by AMS (‰)
14
Conventional C age (BP, ±1r)
Calibrated date (OxCal4.1, possible age range in 1r error, probability)
Lab. Code No. (NUTA2-)
7.3 ± 1.0 6.4 ± 1.0 6.9 ± 1.0 3.5 ± 1.0 4.2 ± 1.0 6.0 ± 1.0 6.4 ± 1.0 8.1 ± 1.0 6.0 ± 1.0 6.2 ± 1.0 5.3 ± 1.0 4.9 ± 1.0 7.2 ± 1.0 5.9 ± 1.0 3.0 ± 1.0 4.1 ± 1.0
7227 ± 34 6938 ± 34 6919 ± 34 7197 ± 34 7129 ± 34 7252 ± 34 7237 ± 34 7292 ± 35 7334 ± 34 7302 ± 34 7311 ± 34 7441 ± 34 7419 ± 35 7340 ± 35 7541 ± 34 7413 ± 34
7733–7644 cal BP (68.2%) 7478–7414 cal BP (68.2%) 7470–7400 cal BP (68.2%) 7693–7610 cal BP (68.2%) 7636–7566 cal BP (68.2%) 7756–7666 cal BP (68.2%) 7742–7654 cal BP (68.2%) 7799–7700 cal BP (68.2%) 7847–7748 cal BP (68.2%) 7814–7714 cal BP (68.2%) 7823–7724 cal BP (68.2%) 7943–7862 cal BP (68.2%) 7926–7846 cal BP (68.2%) 7855–7753 cal BP (68.2%) 8030–7946 cal BP (68.2%) 7923–7842 cal BP (68.2%)
12861 12862 12863 12877 12878 12864 12867 12868 12869 12870 12871 12872 12873 12876 12879 12880
25.8 ± 1.0
6917 ± 27
7784–7774 cal BP (8.5%), 7760–7695 cal BP (59.7%)
13659
27.5 ± 1.0 30.7 ± 1.0
6891 ± 27 6924 ± 27
7740–7679 cal BP (68.2%) 7786–7770 cal BP (14.5%), 7764–7704 cal BP (53.7%)
13667 13660
27.4 ± 1.0
7018 ± 33
14003
25.7 ± 1.0
6949 ± 27
7930–7892 cal BP (29.5%), 7874–7826 cal BP (36.4%), 7804–7799 cal BP (2.3%) 7826–7804 cal BP (15.2%), 7798–7733 cal BP (53.0%)
25.3 ± 1.0
7012 ± 27
26.2 ± 1.0
7008 ± 27
29.5 ± 1.0
7126 ± 84
of Midden No. 1, and from H-belt of Midden No. 2, respectively. The sample levels of the thick shell accumulations were divided into five horizons: uppermost, upper, middle, lower and lowermost, as shown in Tables 2 and 3. It is clearly shown that shell samples are older by about 300–400 14C yr as the result of the marine car-
7926–7896 cal BP (28.1%), 7870–7827 cal BP (38.6%), 7802–7800 cal BP (1.6%) 7925–7898 cal BP (23.9%), 7868–7824 cal BP (37.7%), 7807–7797 cal BP (6.6%) 8020–7915 cal BP (48.3%), 7906–7851 cal BP (19.9%)
13664 13665 13666 13668
bon reservoir effect. The local reservoir correction, DR, was estimated previously to be 60 ± 35 14C yr, based on seven pairs of marine and terrestrial samples that were collected from the identical layers [6]. In addition, it appears that 14C ages are younger in upper sample levels.
685
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687 Table 4 14 C ages and calibrated dates for shell and charcoal remains collected from different horizons at Trench No. 3 of Kimhae shell midden, southern Korea. Sample No.
Layer No.
Dated material
d13CPDB by AMS (‰)
Conventional (BP, ±1r)
SH-1 CH-1 SH-2 CH-2
1 1 8 8
Clam shell Charcoal Clam shell Charcoal
1.0 ± 1.0 25.6 ± 1.0 1.2 ± 1.0 26.1 ± 1.0
2156 ± 22 1910 ± 34 2161 ± 22 1787 ± 22
SH-3 SH-4 CH-3 SH-5 SH-6 CH-4 CH-5 CH-6 SH-7 SH-8 CH-7 CH-8 SH-9 CH-9
14 17 17 31 48 48 55 68 68 74 74 78 80 80
Clam shell Clam shell Charcoal Clam shell Clam shell Charcoal Charcoal Charcoal Clam shell Clam shell Charcoal Charcoal Clam shell Charcoal
2.2 ± 1.0 2.1 ± 1.0 24.1 ± 1.0 2.6 ± 1.0 0.2 ± 1.0 27.3 ± 1.0 26.8 ± 1.0 26.3 ± 1.0 1.4 ± 1.0 1.9 ± 1.0 25.3 ± 1.0 25.7 ± 1.0 1.3 ± 1.0 25.4 ± 1.0
2267 ± 28 2211 ± 23 1848 ± 23 2210 ± 27 2223 ± 27 1844 ± 22 1882 ± 27 1890 ± 27 2291 ± 28 2305 ± 23 2069 ± 23 1910 ± 22 2287 ± 22 1992 ± 27
CH-10 CH-11 CH-13 SH-10
83 88 94 95
Charcoal Charcoal Charcoal Clam shell
24.1 ± 1.0 24.4 ± 1.0 28.0 ± 1.0 0.3 ± 1.0
2002 ± 27 1958 ± 27 2082 ± 28 2321 ± 23
14
C age
Calibrated date (OxCal4.1, possible age range in 1r error, probability)
Lab. Code No. (NUTA2-)
160–241 cal AD (68.2%) 58–128 cal AD (68.2%) 155–236 cal AD (68.2%) 176–190 cal AD (5.8%), 212–258 cal AD (46.4%), 296–320 cal AD (16.0%) 34–118 cal AD (68.2%) 92–175 cal AD (68.2%) 129–180 cal AD (44.3%), 186–214 cal AD (23.9%) 90–180 cal AD (68.2%) 79–162 cal AD (68.2%) 131–214 cal AD (68.2%) 73–138 cal AD (64.8%), 198–206 cal AD (3.4%) 74–132 cal AD (68.2%) 8–91 cal AD (68.2%) 4 cal BC–75 cal AD (68.2%) 146–143 cal BC (2.1%), 111–45 cal BC (66.1%) 70–125 cal AD (68.2%) 16–90 cal AD (68.2%) 38–28 cal BC (9.4%), 22–10 cal BC (12.8%), 2 cal BC–28 cal AD (34.7%), 39–50 cal AD (11.3%) 40 cal BC–24 cal AD (68.2%) 17–74 cal AD (68.2%) 158–134 cal BC (17.0%), 116–52 cal BC (51.2%) 23 cal BC–56 cal AD (68.2%)
9660 12329 9568 9654 10175 9661 9656 9662 9664 9709 11825 11826 10176 9665 9657 9711 9569 9658 11827 11828 11830 9666
Table 5 Sedimentation period for Middens Nos. 1 and 2 at Higashimyo and for shell midden at Kimhae. Items
Uppermost layer (2r) Lowermost layer (2r) Age diff. of upper- and lower-most layers
2r range (yr) Median (yr)
1F-Belt, No. 1 shell midden, Higashimyo
H-Belt, No. 2 shell midden, Higashimyo
Shell midden, Kimhae
Marine shell (cal BP)
Terrestrial nut (cal BP)
Marine shell (cal BP)
Terrestrial nut (cal BP)
Marine shell (cal BP)
Charcoal (cal BP)
Lower limit
Upper limit
Lower limit
Upper limit
Lower limit
Upper limit
Lower limit
Upper limit
Lower limit
Upper limit
Lower limit
Upper limit
7820 7980 40
7590 7820 350
7970 8040 0
7770 7940 230
7720 8070 220
7510 7840 520
7790 8030 0
7670 7790 340
1780 2060 160
1620 1910 410
1770 2080 180
1580 1920 450
180
70
The Bayesian analysis method in OxCal4.1 [10] was used to analyze the temporal sequence of sedimentation for the shell middens at Higashimyo and Kimhae using the 14C dates of shell and terrestrial plant (and charcoal) samples collected from the relevant layers forming the shell middens given in Tables 2–4. In the program, the ‘‘sequence’’ command was applied for a set of 14C ages obtained for all of the sediment layers at both sites. In the case of Middens Nos. 1 and 2 at Higashimyo, 14C ages were divided into 3 or 4 groups (uppermost, upper, middle, lower, lowermost) depending on the structures of the sediments. The first results of the sequence analysis were not acceptable because of warnings of poor agreement for some 14C ages. Then two 14C ages for the shell samples H3–H2 and H3–H3 (Midden No. 2) were eliminated, owing to poor agreement with those of other samples belonging to the same horizon group. It is thought that these two shell samples could be contamination from upper layers. In addition, for single-year 14C ages of nut samples, the sample standard deviation was increased by an additional eight 14C yr [11]. On the basis of calendar ages with 2r probabilities at the top and the bottom boundaries of the sediment layers obtained with the Bayesian analysis, we estimated the starting and ending time of sediment accumulation (‘‘boundary’’ command in OxCal4.1) as well as the spanning time of sedimentation (‘‘span’’ command), as shown in Table 5. There is a small but clear disagreement in the estimation of accumulation period based on marine and terrestrial samples. We prefer
350
180
260
290
to use the results from terrestrial samples, due to the unknown effect on marine sample results from the marine reservoir effect. The results are illustrated in Fig. 3. According to 14C ages from nut samples, the accumulation of Midden No. 1 started at around 8050–7950 cal BP which is almost identical with 8050–7800 cal BP for Midden No. 2. Accumulation of Midden No. 1 finished at around 7950–7750 cal BP, about 100 cal yr earlier than that of No. 2 shellmidden (7800– 7650 cal BP), possibly because the former was situated at lower elevation and closer to the tidal front. It is estimated that the duration spans are 100 cal yr and 200 cal yr for Middens Nos. 1 and 2, respectively. These rather short accumulation periods are consistent with archeological findings that only two typological changes (Senokan-B and Todoroki-A types) were recognized for pottery fragments unearthed from the shell middens. 4.2. Kimhae shellmiddens Table 4 shows values of d13C, 14C age and calibrated ages for shell and charcoal remains that were collected from different horizons of the 9 m-deep pit wall. A 14C age vs. depth profile is shown in Fig. 4. The profile for the shell samples is almost linear, but the one for the charcoal samples has some outliers that are older than the expected tendency. We suggest that this can be explained by an ‘‘old wood’’ effect where the charcoal samples are derived from the inner rings of huge trees. Shell samples are older than the asso-
686
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
charcoal samples collected from the identical or nearby horizons, and published previously [4,6]. The obtained DR value was 21 ± 34 14C yr, excluding three pairs (SH-1 and CH-1, SH-8 and CH-7, SH-10 and CH-13) whose charcoal 14C ages were far older than respective expected values. The Bayesian approach was also used to analyze the temporal sequence of sedimentation for the Kimhae site. The 14C ages for charcoal samples CH-1, CH-7 and CH-13 in Table 4 were eliminated for the analyses of Kimhae samples because of poor agreement with other 14C ages. The 14C age of a shell sample SH-3 was also anomalous and eliminated (layer No. 14). This sample may have come from the deeper horizons. Estimation of the time required to produce the 9 m thick shell midden at the Kimhae site is summarized in Table 5. The resulting age-depth profiles were almost identical for both kinds of samples. The shell accumulation was started at around the middle of the 1st C BC and finished at around the middle of the 3rd C AD. The time required to accumulate the full 9 m thick shell midden was estimated to be about 250–300 cal yr.
5. Summary
Fig. 3. Altitude and age of sediment accumulation for Middens Nos. 1 and 2 at Higashimyo.
Fig. 4. 14C ages of shell and charcoal samples from the stratified layers at Kimhae. Numerical figures at each data point are layer numbers counted from the top to the bottom of the midden.
ciated charcoal by about 300–400 14C yr as the result of the marine reservoir effect. Estimation of the local marine reservoir correction, DR, was obtained by using nine pairs of 14C ages from shell and
We have conducted 14C dating of terrestrial and marine materials collected from two lowland shell middens, the Higashimyo site in Japan and the Kimhae site in Korea. The results obtained for both sites are summarized in the following. Higashimyo site: (1) More than 750 storage pits were unearthed near the shell middens. Nuts preserved in the baskets and plant materials from the pits were dated and their 14C ages were compared with the elevation of the pits. No clear pattern was found between the 14C ages and the location of the storage pits. The calibrated dates of the storage pits were within two hundred years from 8000 to 7800 cal BP. (2) Significant age difference was obtained for terrestrial and marine materials collected from identical horizons. 14C ages of the former were younger by 300–400 yrs than those of the latter. The local reservoir correction, DR, was estimated to be 60 ± 35 14C yr. (3) 14C ages for nut samples suggest that accumulation of Midden No. 1 started at around 8050–7950 cal BP and ended at 7950–7750 cal BP, lasting for ca. 100 cal yr, while accumulation of Midden No. 2 started at around 8050–7800 cal BP and ended at 7800–7650 cal BP, lasting for ca. 200 cal yr. The minor age disagreement probably results from the different locations of the individual middens (Midden No. 1 was formed at a lower level than No. 2). These rather short accumulation periods are consistent with archeological findings that only two types of pottery fragments were unearthed from the shell middens. Kimhae site: (4) A clear 14C age difference was also obtained for terrestrial and marine materials collected from the identical horizons for this site. 14C ages of the former were younger by 300– 400 yrs than those of the latter. The local reservoir correction, DR, was estimated to be 21 ± 34 14C yr from six pairs of terrestrial and marine materials. (5) Formation of the midden at the south wall of Trench 3 started at around the middle of the 1st C cal BC and ended at the middle of the 3rd C cal AD, lasting for ca. 250– 300 cal yr. This time range is coincident with the period of the Proto-Three Kingdoms of Korea (1st C BC to mid-4th C AD), when many agricultural people inhabited the Kimhae region and might have built the shell midden.
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
Acknowledgments The authors would like to thank the members of the Board of Education of Saga city, Japan, and the Foundation of Sanko Institute for Cultural Properties, Korea, for supplying us kindly the excavated samples. This work was supported partly by the ‘‘Grant-in aid for Scientific Research’’ of the Japan Society of the Promotion of Science (JSPS) (subject Nos. 15202023, 16320108 and 22240082). References [1] Saga Municipal Board of Education, The Higashimyo wetland site – the basket maker of the Jomon period around 7000 BP, 2008, p. 12.
687
[2] Saga City Board of Education, Excavation Report of Higashimyo Archeological Site Group-II, No. 6, 2009, p. 328 (in Japanese). [3] A. Matsui, Archaeological Quarterly 113 (2010) 96 (in Japanese). [4] Sanko Institute for Cultural Properties, Excavation Report of Kimhae Heohyeon-ni Site, 2009, p. 458 (in Korean). [5] T. Nakamura, E. Niu, H. Oda, A. Ikeda, M. Minami, T. Ohta, T. Oda, Nucl. Instrum. Methods B223–224 (2004) 124. [6] T. Nakamura, I. Nishida, H. Takada, M. Okuno, M. Minami, H. Oda, Nucl. Instrum. Methods B259 (2007) 453. [7] C. Bronk Ramsey, Radiocarbon 43 (2001) 355. [8] C. Bronk Ramsey, Radiocarbon 51 (2009) 337. [9] P.J. Reimer, M.G.L. Baillie, E. Bard, A. Bayliss, J.W. Beck, P.G. Blackwell, C. Bronk Ramsey, C.E. Buck, G.S. Burr, R.L. Edwards, M. Friedrich, P.M. Grootes, T.P. Guilderson, I. Hajdas, T.J. Heaton, A.G. Hogg, K.A. Hughen, K.F. Kaiser, B. Kromer, F.G. McCormac, S.W. Manning, R.W. Reimer, D.A. Richards, J.R. Southon, S. Talamo, C.S.M. Turney, J. van der Plicht, C.E. Weyhenmeyer, Radiocarbon 51 (2009) 1111. [10] C. Bronk Ramsey, Quaternary Science Reviews 27 (1-2) (2008) 42. [11] M. Stuiver, P.J. Reimer, E. Bard, J.W. Beck, G.S. Burr, K.A. Hughen, F.G. Kromer, J. van der Plicht, M. Spurk, Radiocarbon 40 (3) (1998) 1041.
Contents lists available at SciVerse ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Time range for accumulation of shell middens from Higashimyo (western Japan) and Kimhae (southern Korea) by AMS radiocarbon dating Toshio Nakamura a,⇑, Akira Matsui b, Iwao Nishida c, Mitsuru Nakano c, Takayuki Omori d a
Center for Chronological Research, Nagoya University, Chikusa, Nagoya 464-8602, Japan National Research Institute for Cultural Properties, Nara, Nijyo-cho, Nara 630-8577, Japan c The Saga-City Board of Education, Sakae-machi, Saga 840-8501, Japan d University Museum, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan b
a r t i c l e
i n f o
Article history: Received 31 July 2011 Received in revised form 29 August 2012 Available online 25 October 2012 Keywords: Shell midden Accumulation time Bayesian analysis 14 C age Higashimyo site Kimhae site
a b s t r a c t Numerous large and small shell middens have been reported throughout the world. An interesting question is when the huge and thick shell middens were formed, and how many years were required to build up the whole midden. Shell middens contain not only shell fragments but also organic substances such as bones, nuts, acorn, and plant residues, which are suitable substances with which to establish 14C chronology of the middens. We have conducted 14C dating on terrestrial and marine materials collected from two lowland shell middens, the Higashimyo site in Japan (the Earliest Jomon period) and the Kimhae site in Korea (the Proto-Three Kingdom period), to establish high precision 14C chronologies and determine the time required for shell accumulation. According to Bayesian analysis of 14C ages from terrestrial samples, accumulation of Midden No. 1 at Higashimyo (altitude from 1.1 to 2.3 m a.s.l., Dd = 1.2 m) started at around 8050–7950 cal BP and ended at 7950–7750 cal BP, lasting for ca. 100 cal yr, while accumulation of Midden No. 2 (altitude from 0.5 to 2.0 m a.s.l., Dd = 1.5 m) started at around 8050–7800 cal BP and ended at 7800–7650 cal BP, lasting for ca. 200 cal yr. Thus the Midden No. 1 was abandoned a bit earlier than Midden No. 2, but the time range for sediment accumulation overlaps each other. Accumulation at the Kimhae shell midden (altitude from 5 to 14 m a.s.l., Dd = 9 m) started at around the middle of the 1st C cal BC and ended at around the middle of the 3rd C cal AD, lasting for ca. 250 to 300 cal yr. Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction It is an archeologically interesting question when huge and thick shell middens were formed, and how long it took to build them up. Pottery fragments excavated from middens can be analyzed to estimate the age as well as their accumulation time on the basis of the typological evidence. However, since available pottery fragments are limited, the estimation of the age and the accumulation time can be less reliable than expected. Shell middens contain not only shell fragments but also organic substances such as bones, nuts, acorn, and plant residues, which are suitable substances to use to establish a 14C chronology of the midden. In this article, we focus on two shell middens: the Higashimyo shell midden in Saga prefecture, southeast of Japan, and the Kimhae shell midden, Kimhae city, south of Korea. The Higshimyo site is a wetland shell midden formed during the earliest Jomon period (10,000–6000 cal BP) [1]. The Higashimyo site is composed of six shell middens produced separately at the intertidal zone during the marine transgression in the Holocene ⇑ Corresponding author. Tel.: +81 52 789 3082; fax: +81 52 789 3092. E-mail address: [email protected] (T. Nakamura). 0168-583X/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nimb.2012.08.047
period after the final ice age, and was abandoned as the result of rising sea level. We have measured 14C ages of shell, nut, acorn, wood, and herbaceous-plant remains excavated from the shell middens in order to analyze and establish the accurate chronology of the site [2]. The Kimhae shell midden, formed in the Proto-Three Kingdom period (1st C BC to mid-4th C AD), consists of 9 m deep sediments from 14 m a.s.l. down to 5 m a.s.l., including numerous huge oyster shells and big clamshells (Meretrix lusoria), intercalated with clear charcoal layers or charcoal fragmental lumps [3]. Using several pairs of shell and charcoal material from the same horizon of the sediment, we analyzed the time range required for sediment accumulation. 2. Archeological sites 2.1. Higashimyo archeological site The Higashimyo archeological site consists of a dry residential area and six shell middens located in the huge Saga Plain, the largest plain in western Japan, at the northern part of Kyushu Island (Fig. 1) [1]. The Saga plain faces south onto the innermost part of
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
681
Fig. 1. Location of Higashimyo and Kimhae sites and layout of Nos. 1–6 middens at Higashimyo.
Ariake bay, a bay extending 20 km wide in the east–west and 60 km long in the south–north directions with relatively shallow water depths (ca. 20 m on average). The Higashimyo midden was formed on the coastline at an early stage of the maximum transgression period (8–6 ka cal BP) and sank by means of successive sea-level rise. The range of high and low tides is about 5 m at the innermost part of Ariake bay, so many storage pits were placed in the intertidal zone. Of greatest archeological interest is the fact that more than 750 baskets woven with twisted ropes made of thinly sliced wood were unearthed along with plenty of nuts and acorns preserved inside them. The woven wooden baskets excavated here are the oldest (ca. 7800–7900 cal BP) ones recorded in the earliest Jomon period. At the residential area on the dry high terrace (ca. 3 m a.s.l.), about 50 m east from Middens Nos. 1 and 2, fireplaces with many charred stones and a presumed burial containing more than five people have been unearthed [1]. A huge number of shell fragments were accumulated in the Higashimyo shell middens. Six shell middens were detected separately at the Higashimyo site, extending about 400 m in the south–north direction, and numbered 1 to 5 from south–north. Midden No. 6 is located in the southern most part of the site and was discovered last (Fig. 1). Lengths and areas of the shell middens were 30 and 300, 40 and 400, 20 and 200, 45 and 430, 15 and 40, and 55 m and 330 m2, for Middens No. 1 to No. 6, respectively.
Middens Nos. 1 and 2 were intensively excavated. In Midden No. 1, the thickness of the mound was ca. 1.2 m and the elevations of the lowermost and uppermost levels were 2.3 and 1.1 m a.s.l. For Midden No. 2, the respective values were 1.5 m, and 2.0 and 0.5 m a.s.l. We have collected shell fragments and terrestrial plant remains from the full layers, from the bottom to the top, of the two middens for 14C dating, in order to estimate the time required to accumulate the total volume of the middens. Four kinds of shell fragments were mainly collected at the site. They were Japanese corbicula (Corbicula japonica), cockles (Fegillarea granosa), jackknife clams or razor shell (Sinonovacula constricta), and oyster (Crassostrea gigas Crassostrea ariakesis). We normally used cockles for dating because of its potential strength against surface weathering. We also collected terrestrial plant remains consisting of twigs, wooden stakes, acorns, fragments of wooden sticks used to make up a basket, wooden twisted cords, wooden boards, etc., which were less likely to show ‘‘old wood’’ effect. 2.2. Kimhae Heohyeon-ni shellmidden The Kimhae Heohyeon-ni shell midden is located at Kimhae city along the lower Nakdong-gang river, on the alluvial plain formed by filling the paleo-Kimhae bay with deposits supplied by the Nakdong-gang river (Fig. 1) [3]. The midden was first excavated
682
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
Table 1 14 C ages and calibrated dates for plant remains collected from storage pits situated at four different horizons at Higashimyo. No.
Storage pit No.
Layer
Dated material
Upper horizon 1 SK2002
Uppermost
2
SK2002
Uppermost
3
SK2002
4
SK2001
Lower part of 5th layer East half of 2nd layer
Wooden stake (K22666) Wooden stake (K20011) Acorn (Quercus aliena) Acorn (Quercus aliena) Acorn (Quercus gilva) Woven basket (AM2250) Wood plate Acorn (Quercus gilva) Acorn (Quercus gilva) Woven basket
Middle horizon 5 SK2106
–
6
SK2106
–
7 8
SK2106 SK2095
– Southern half
9
SK2093
Southern half
10
SK2093
3rd layer
d13CPDB by AMS (‰)
Conventional 14C age (BP, ±1r)
Calibrated date.(OxCal4.1, possible age range in 1r error, probability)
Lab. Code No. (NUTA2-)
27.5 ± 1.0
6574 ± 26
7485–7434 cal BP (68.2%)
13661
30.6 ± 1.0
6567 ± 27
7481–7433 cal BP (68.2%)
13662
24.0 ± 1.0
6624 ± 36
13855
26.8 ± 1.0
6985 ± 33
7565–7532 cal BP (30.9%).7520–7480 cal BP (37.3%) 7920–7902 cal BP (10.3%).7861–7786 cal BP (57.9%)
26.6 ± 1.0
7029 ± 34
BP (34.9%).7878–7838 cal BP
13370
31.0 ± 1.0
7072 ± 33
BP (27.6%).7900–7864 cal BP
13372
29.7 ± 1.0 25.5 ± 1.0
7042 ± 36 7054 ± 39
BP (68.2%) BP (19.2%).7906–7850 cal BP
13363 13200
24.7 ± 1.0
6963 ± 34
7931–7890 cal (33.3%) 7950–7922 cal (40.6%) 7932–7848 cal 7937–7914 cal (49.0%) 7840–7740 cal
BP (68.2%)
13368
28.4 ± 1.0
6993 ± 33
7922–7900 cal BP (13.8%).7864–7790 cal BP (54.4%)
13536
13519
Middle to lower horizon 11 SK2138 East half of 4th layer 12 SK2138 – 13 SK2138 –
Acorn (Quercus aliena) Woven basket Rope made of plant
26.0 ± 1.0
6968 ± 40
7848–7735 cal BP (68.2%)
13203
30.9 ± 1.0 30.8 ± 1.0
6882 ± 39 7116 ± 37
13205 13359
14
–
Wooden plate
27.7 ± 1.0
7044 ± 33
7754–7670 cal BP (68.2%) 7976–7930 cal BP (56.3%).7892–7876 cal BP (11.9%) 7932–7850 cal BP (68.2%)
Acorn (Quercus aliena) Acorn (Quercus acutissima) Woven basket(Sapindaceae) Acorn (Quercus aliena) Acorn (Quercus acutissima) Woven basket
27.2 ± 1.0
7122 ± 33
13535
26.2 ± 1.0
7114 ± 32
30.5 ± 1.0
6945 ± 47
7979–7932 cal BP (63.3%).7888–7880 cal BP (4.9%) 7972–7932 cal BP (59.3%).7889–7878 cal BP (8.9%) 7830–7710 cal BP (68.2%)
30.3 ± 1.0
7111 ± 32
28.3 ± 1.0
7092 ± 34
30.2 ± 1.0
7008 ± 40
SK2138
Lower horizon 15 SK2006 16
SK2056
Northern part of 6, 7th layer 10th layer
17
SK2056
–
18
SK2143
–
19
SK2134
–
20
SK2134
–
in 1920 by Japanese archeologists. Following several successive excavations, a large-scale excavation survey by the Sanko Institute of Cultural Properties, Korea, was carried out at the site in 2005 [4]. Three trenches as deep as 9 m, at a height of 14 m down to 5 m a.s.l., were dug, and numerous shell fragments, intercalated with clear charcoal layers or charcoal fragmental lumps, were detected on the walls. A columnar sample of 30 30 cm2 from the top to the bottom of the trench was analyzed for shell assemblages, and a total of 5912 shells were recorded. The main components of the shells are: 36.6% Pacific oyster (Crassostrea gigas), 14.1% marsh snails (Semisulcospira bensoni), 8.8% horn shells (Batillaria multiformis), and 7.5% chowder clams (Meretrix lusoria) [4]. The sediment at the south wall of Trench No. 3 was classified stratigraphically into 113 layers. We collected pairs of chowder clamshell and charcoal material from 54 individual layers extending from top to bottom of the 9 m deep sediment to establish a high-precision 14C chronology and estimate the time range required for sediment accumulation. Large clamshell with a smooth surface is preferable for 14C dating rather than oyster shells which possess banded surface structures and could possibly be contaminated with foreign carbon.
7970–7930 cal BP (56.4%).7890–7877 cal BP (11.8%) 7960–7927 cal BP (41.2%).7896–7871 cal BP (27.0%) 7926–7896 cal BP (20.3%).7870–7794 cal BP (47.9%)
13362
11823 13212 11824 13371 13204
3. Experimental The nut and wood samples were processed with acid–alkali– acid treatments, rinsed with distilled water and dried. A part of the pre-treated sample was combusted to CO2 [5]. The shell samples were rinsed with diluted HCl (0.6 M) as well as distilled water in an ultrasonic cleaner, dried and powdered. The shell powder was decomposed with 95% H3PO4 in an evacuated bottle to produce CO2 [6]. CO2 was reduced to graphite on an iron catalyst under hydrogen atmosphere. All three carbon isotopes in graphite targets prepared from samples, NIST HOxII standard and 14C blank (oxalic acid synthesized from fossil fuel) were measured with an AMS system (HVEE model-4130) at Nagoya University [5]. The measured 14 12 C/ C and 13C/12C ratios were used to calculate the sample conventional 14C age. The obtained 14C ages were converted to calendar dates by using the calibration program OxCal 4.1 [7,8] and IntCal09 and Marine09 calibration data sets [9]. We have estimated the local marine reservoir correction, DR, in the present analysis, but the obtained DR values were less reliable with rather large errors. Since DR values were almost consistent with zero, we adopted DR = 0 for calibration of marine samples.
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
683
Fig. 2. Calibrated dates for plant remains collected from storage pits at Higashimyo.
4. Results and discussion 4.1. Higashimyo archeological site 4.1.1. Plant remains from storage pits Values of d13C, 14C age and calibrated ages are given in Table 1 for plant remains collected from storage pits situated at four different horizons: upper, middle, middle to lower and lower. Storage pits are located in the tidal range, because underwater storage of nuts is necessary for stable preservation, and also it is easy to approach the pit location whenever necessary. At the time of transgression, it would normally be expected that the calibrated ages become
younger, as the elevation of the storage pit increases. However, this tendency is not clear. This is because the tidal range (the vertical difference between the high tide and succeeding low tide) at the site is as large as 5 m. Since there was a huge area in which to make a new storage pit, a newer pit did not have to be located at a higher level. Except for the pit SK2002, all other storage pits were produced within two hundred years from 8000 to 7800 cal BP (Fig. 2). 4.1.2. 14C results for Middens Nos. 1 and 2 Tables 2 and 3 show values of d13C, 14C age and calibrated ages for marine shell and nut remains that were collected from different horizons in the 1F-belt and corresponding layers at No. 21 section
684
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
Table 2 14 C ages and calibrated dates for Cockles and nut remains collected from 1F belt and corresponding layers at No. 21 section of No. 1 shell midden at Higashimyo. No. Shell 1 2 3 4 5 6 7 8 9
Section No.
Horizon
samples collected from 1F 1F5–H1 Upper 1F5–H2 Upper 1F5–H3 Upper 1F24–H1 Middle 1F24–H2 Middle 1F24–H3 Middle 1F37–H1 Lower 1F37–H2 Lower 1F37–H3 Lower
Dated material belt of No. 1 shell midden Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell
d13CPDB by AMS (‰) 4.6 ± 1.0 5.8 ± 1.0 5.3 ± 1.0 5.3 ± 1.0 4.5 ± 1.0 4.4 ± 1.0 4.5 ± 1.0 5.7 ± 1.0 6.1 ± 1.0
Nut remains collected from No. 21 section(corresponding to 1F belt) 10 21–9–3 Upper Walnut (Juglans mandshurica 24.5 ± 1.0 var. sieboldiana) 11 21–57–1 Middle Walnut (Juglans mandshurica 24.9 ± 1.0 var. sieboldiana) 12 21–57–2 Middle Walnut (Juglans mandshurica 25.6 ± 1.0 var. sieboldiana) 13 21–94–1 Lower Acorn (Quercus gilva) 25.7 ± 1.0 14 21–94–2 Lower Acorn (Quercus gilva) 25.9 ± 1.0 15 21–94–3 Lower Acorn (Quercus gilva) 24.8 ± 1.0
Conventional 14C age (BP, ±1r)
Calibrated date (OxCal4.1,possible age range in 1r error, probability)
Lab. Code No. (NUTA2 )
7295 ± 34 7217 ± 35 7335 ± 34 7351 ± 34 7319 ± 34 7400 ± 34 7421 ± 34 7362 ± 35 7425 ± 34
7803–7704 cal 7724–7631 cal 7848–7748 cal 7866–7766 cal 7830–7733 cal 7916–7833 cal 7928–7848 cal 7885–7780 cal 7930–7851 cal
(68.2%) (68.2%) (68.2%) (68.2%) (68.2%) (68.2%) (68.2%) (68.2%) (68.2%)
13556 13557 13558 13559 13560 13563 13564 13565 13566
7071 ± 36
7951–7920 cal BP (27.3%).7902–7860 cal BP (40.9%) 7954–7922 cal BP (30.4%).7900–7864 cal BP (37.8%) 7973–7930 cal BP (54.1%).7892–7875 cal BP (14.1%) 7997–7937 cal BP (68.2%) 8008–7954 cal BP (68.2%) 8000–7950 cal BP (68.2%)
13849
7076 ± 36 7112 ± 37 7135 ± 37 7162 ± 39 7150 ± 37
BP BP BP BP BP BP BP BP BP
13850 13851 13852 13853 13854
Table 3 14 C ages and calibrated dates for shell and nut remains collected from different horizons at H belt of No 2. shell midden at Higashimyo. No.
Shell 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Section No.
Horizon
samples collected from H belt H3–H1 Uppermost H3–H2 Uppermost H3–H3 Uppermost H3–O1 Uppermost H3–O2 Uppermost H6–H1 Upper H6–H2 Upper H6–H3 Upper H15–H1 Middle H15–H2 Middle H15–H3 Middle H34–H1 Lowermost H34–H2 Lowermost H34–H3 Lowermost H34–O1 Lowermost H34–O2 Lowermost
Dated material
of No. 2 shell midden Cockles shell Cockles shell Cockles shell Oyster shell Oyster shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Cockles shell Oyster shell Oyster shell
Acorn and walnut remains collected from H belt of No. 2 shell midden 17 W–H6–b Upper Walnut (Juglans mandshurica var. sieboldiana) 18 A–H6–b Upper Acorn (Quercus gilva) 19 W–H7 Upper Walnut (Juglans mandshurica var. sieboldiana) 20 W–H14–1 middle Walnut (Juglans mandshurica var. sieboldiana) 21 W–H15 Middle Walnut (Juglans mandshurica var. sieboldiana) 22 W–H29–1 Lower Walnut (Juglans mandshurica var. sieboldiana) 23 W–H34–1 Lowermost Walnut (Juglans mandshurica var. sieboldiana) 24 W–H39–1 Lowermost Walnut (Juglans mandshurica var. sieboldiana)
d13CPDB by AMS (‰)
14
Conventional C age (BP, ±1r)
Calibrated date (OxCal4.1, possible age range in 1r error, probability)
Lab. Code No. (NUTA2-)
7.3 ± 1.0 6.4 ± 1.0 6.9 ± 1.0 3.5 ± 1.0 4.2 ± 1.0 6.0 ± 1.0 6.4 ± 1.0 8.1 ± 1.0 6.0 ± 1.0 6.2 ± 1.0 5.3 ± 1.0 4.9 ± 1.0 7.2 ± 1.0 5.9 ± 1.0 3.0 ± 1.0 4.1 ± 1.0
7227 ± 34 6938 ± 34 6919 ± 34 7197 ± 34 7129 ± 34 7252 ± 34 7237 ± 34 7292 ± 35 7334 ± 34 7302 ± 34 7311 ± 34 7441 ± 34 7419 ± 35 7340 ± 35 7541 ± 34 7413 ± 34
7733–7644 cal BP (68.2%) 7478–7414 cal BP (68.2%) 7470–7400 cal BP (68.2%) 7693–7610 cal BP (68.2%) 7636–7566 cal BP (68.2%) 7756–7666 cal BP (68.2%) 7742–7654 cal BP (68.2%) 7799–7700 cal BP (68.2%) 7847–7748 cal BP (68.2%) 7814–7714 cal BP (68.2%) 7823–7724 cal BP (68.2%) 7943–7862 cal BP (68.2%) 7926–7846 cal BP (68.2%) 7855–7753 cal BP (68.2%) 8030–7946 cal BP (68.2%) 7923–7842 cal BP (68.2%)
12861 12862 12863 12877 12878 12864 12867 12868 12869 12870 12871 12872 12873 12876 12879 12880
25.8 ± 1.0
6917 ± 27
7784–7774 cal BP (8.5%), 7760–7695 cal BP (59.7%)
13659
27.5 ± 1.0 30.7 ± 1.0
6891 ± 27 6924 ± 27
7740–7679 cal BP (68.2%) 7786–7770 cal BP (14.5%), 7764–7704 cal BP (53.7%)
13667 13660
27.4 ± 1.0
7018 ± 33
14003
25.7 ± 1.0
6949 ± 27
7930–7892 cal BP (29.5%), 7874–7826 cal BP (36.4%), 7804–7799 cal BP (2.3%) 7826–7804 cal BP (15.2%), 7798–7733 cal BP (53.0%)
25.3 ± 1.0
7012 ± 27
26.2 ± 1.0
7008 ± 27
29.5 ± 1.0
7126 ± 84
of Midden No. 1, and from H-belt of Midden No. 2, respectively. The sample levels of the thick shell accumulations were divided into five horizons: uppermost, upper, middle, lower and lowermost, as shown in Tables 2 and 3. It is clearly shown that shell samples are older by about 300–400 14C yr as the result of the marine car-
7926–7896 cal BP (28.1%), 7870–7827 cal BP (38.6%), 7802–7800 cal BP (1.6%) 7925–7898 cal BP (23.9%), 7868–7824 cal BP (37.7%), 7807–7797 cal BP (6.6%) 8020–7915 cal BP (48.3%), 7906–7851 cal BP (19.9%)
13664 13665 13666 13668
bon reservoir effect. The local reservoir correction, DR, was estimated previously to be 60 ± 35 14C yr, based on seven pairs of marine and terrestrial samples that were collected from the identical layers [6]. In addition, it appears that 14C ages are younger in upper sample levels.
685
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687 Table 4 14 C ages and calibrated dates for shell and charcoal remains collected from different horizons at Trench No. 3 of Kimhae shell midden, southern Korea. Sample No.
Layer No.
Dated material
d13CPDB by AMS (‰)
Conventional (BP, ±1r)
SH-1 CH-1 SH-2 CH-2
1 1 8 8
Clam shell Charcoal Clam shell Charcoal
1.0 ± 1.0 25.6 ± 1.0 1.2 ± 1.0 26.1 ± 1.0
2156 ± 22 1910 ± 34 2161 ± 22 1787 ± 22
SH-3 SH-4 CH-3 SH-5 SH-6 CH-4 CH-5 CH-6 SH-7 SH-8 CH-7 CH-8 SH-9 CH-9
14 17 17 31 48 48 55 68 68 74 74 78 80 80
Clam shell Clam shell Charcoal Clam shell Clam shell Charcoal Charcoal Charcoal Clam shell Clam shell Charcoal Charcoal Clam shell Charcoal
2.2 ± 1.0 2.1 ± 1.0 24.1 ± 1.0 2.6 ± 1.0 0.2 ± 1.0 27.3 ± 1.0 26.8 ± 1.0 26.3 ± 1.0 1.4 ± 1.0 1.9 ± 1.0 25.3 ± 1.0 25.7 ± 1.0 1.3 ± 1.0 25.4 ± 1.0
2267 ± 28 2211 ± 23 1848 ± 23 2210 ± 27 2223 ± 27 1844 ± 22 1882 ± 27 1890 ± 27 2291 ± 28 2305 ± 23 2069 ± 23 1910 ± 22 2287 ± 22 1992 ± 27
CH-10 CH-11 CH-13 SH-10
83 88 94 95
Charcoal Charcoal Charcoal Clam shell
24.1 ± 1.0 24.4 ± 1.0 28.0 ± 1.0 0.3 ± 1.0
2002 ± 27 1958 ± 27 2082 ± 28 2321 ± 23
14
C age
Calibrated date (OxCal4.1, possible age range in 1r error, probability)
Lab. Code No. (NUTA2-)
160–241 cal AD (68.2%) 58–128 cal AD (68.2%) 155–236 cal AD (68.2%) 176–190 cal AD (5.8%), 212–258 cal AD (46.4%), 296–320 cal AD (16.0%) 34–118 cal AD (68.2%) 92–175 cal AD (68.2%) 129–180 cal AD (44.3%), 186–214 cal AD (23.9%) 90–180 cal AD (68.2%) 79–162 cal AD (68.2%) 131–214 cal AD (68.2%) 73–138 cal AD (64.8%), 198–206 cal AD (3.4%) 74–132 cal AD (68.2%) 8–91 cal AD (68.2%) 4 cal BC–75 cal AD (68.2%) 146–143 cal BC (2.1%), 111–45 cal BC (66.1%) 70–125 cal AD (68.2%) 16–90 cal AD (68.2%) 38–28 cal BC (9.4%), 22–10 cal BC (12.8%), 2 cal BC–28 cal AD (34.7%), 39–50 cal AD (11.3%) 40 cal BC–24 cal AD (68.2%) 17–74 cal AD (68.2%) 158–134 cal BC (17.0%), 116–52 cal BC (51.2%) 23 cal BC–56 cal AD (68.2%)
9660 12329 9568 9654 10175 9661 9656 9662 9664 9709 11825 11826 10176 9665 9657 9711 9569 9658 11827 11828 11830 9666
Table 5 Sedimentation period for Middens Nos. 1 and 2 at Higashimyo and for shell midden at Kimhae. Items
Uppermost layer (2r) Lowermost layer (2r) Age diff. of upper- and lower-most layers
2r range (yr) Median (yr)
1F-Belt, No. 1 shell midden, Higashimyo
H-Belt, No. 2 shell midden, Higashimyo
Shell midden, Kimhae
Marine shell (cal BP)
Terrestrial nut (cal BP)
Marine shell (cal BP)
Terrestrial nut (cal BP)
Marine shell (cal BP)
Charcoal (cal BP)
Lower limit
Upper limit
Lower limit
Upper limit
Lower limit
Upper limit
Lower limit
Upper limit
Lower limit
Upper limit
Lower limit
Upper limit
7820 7980 40
7590 7820 350
7970 8040 0
7770 7940 230
7720 8070 220
7510 7840 520
7790 8030 0
7670 7790 340
1780 2060 160
1620 1910 410
1770 2080 180
1580 1920 450
180
70
The Bayesian analysis method in OxCal4.1 [10] was used to analyze the temporal sequence of sedimentation for the shell middens at Higashimyo and Kimhae using the 14C dates of shell and terrestrial plant (and charcoal) samples collected from the relevant layers forming the shell middens given in Tables 2–4. In the program, the ‘‘sequence’’ command was applied for a set of 14C ages obtained for all of the sediment layers at both sites. In the case of Middens Nos. 1 and 2 at Higashimyo, 14C ages were divided into 3 or 4 groups (uppermost, upper, middle, lower, lowermost) depending on the structures of the sediments. The first results of the sequence analysis were not acceptable because of warnings of poor agreement for some 14C ages. Then two 14C ages for the shell samples H3–H2 and H3–H3 (Midden No. 2) were eliminated, owing to poor agreement with those of other samples belonging to the same horizon group. It is thought that these two shell samples could be contamination from upper layers. In addition, for single-year 14C ages of nut samples, the sample standard deviation was increased by an additional eight 14C yr [11]. On the basis of calendar ages with 2r probabilities at the top and the bottom boundaries of the sediment layers obtained with the Bayesian analysis, we estimated the starting and ending time of sediment accumulation (‘‘boundary’’ command in OxCal4.1) as well as the spanning time of sedimentation (‘‘span’’ command), as shown in Table 5. There is a small but clear disagreement in the estimation of accumulation period based on marine and terrestrial samples. We prefer
350
180
260
290
to use the results from terrestrial samples, due to the unknown effect on marine sample results from the marine reservoir effect. The results are illustrated in Fig. 3. According to 14C ages from nut samples, the accumulation of Midden No. 1 started at around 8050–7950 cal BP which is almost identical with 8050–7800 cal BP for Midden No. 2. Accumulation of Midden No. 1 finished at around 7950–7750 cal BP, about 100 cal yr earlier than that of No. 2 shellmidden (7800– 7650 cal BP), possibly because the former was situated at lower elevation and closer to the tidal front. It is estimated that the duration spans are 100 cal yr and 200 cal yr for Middens Nos. 1 and 2, respectively. These rather short accumulation periods are consistent with archeological findings that only two typological changes (Senokan-B and Todoroki-A types) were recognized for pottery fragments unearthed from the shell middens. 4.2. Kimhae shellmiddens Table 4 shows values of d13C, 14C age and calibrated ages for shell and charcoal remains that were collected from different horizons of the 9 m-deep pit wall. A 14C age vs. depth profile is shown in Fig. 4. The profile for the shell samples is almost linear, but the one for the charcoal samples has some outliers that are older than the expected tendency. We suggest that this can be explained by an ‘‘old wood’’ effect where the charcoal samples are derived from the inner rings of huge trees. Shell samples are older than the asso-
686
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
charcoal samples collected from the identical or nearby horizons, and published previously [4,6]. The obtained DR value was 21 ± 34 14C yr, excluding three pairs (SH-1 and CH-1, SH-8 and CH-7, SH-10 and CH-13) whose charcoal 14C ages were far older than respective expected values. The Bayesian approach was also used to analyze the temporal sequence of sedimentation for the Kimhae site. The 14C ages for charcoal samples CH-1, CH-7 and CH-13 in Table 4 were eliminated for the analyses of Kimhae samples because of poor agreement with other 14C ages. The 14C age of a shell sample SH-3 was also anomalous and eliminated (layer No. 14). This sample may have come from the deeper horizons. Estimation of the time required to produce the 9 m thick shell midden at the Kimhae site is summarized in Table 5. The resulting age-depth profiles were almost identical for both kinds of samples. The shell accumulation was started at around the middle of the 1st C BC and finished at around the middle of the 3rd C AD. The time required to accumulate the full 9 m thick shell midden was estimated to be about 250–300 cal yr.
5. Summary
Fig. 3. Altitude and age of sediment accumulation for Middens Nos. 1 and 2 at Higashimyo.
Fig. 4. 14C ages of shell and charcoal samples from the stratified layers at Kimhae. Numerical figures at each data point are layer numbers counted from the top to the bottom of the midden.
ciated charcoal by about 300–400 14C yr as the result of the marine reservoir effect. Estimation of the local marine reservoir correction, DR, was obtained by using nine pairs of 14C ages from shell and
We have conducted 14C dating of terrestrial and marine materials collected from two lowland shell middens, the Higashimyo site in Japan and the Kimhae site in Korea. The results obtained for both sites are summarized in the following. Higashimyo site: (1) More than 750 storage pits were unearthed near the shell middens. Nuts preserved in the baskets and plant materials from the pits were dated and their 14C ages were compared with the elevation of the pits. No clear pattern was found between the 14C ages and the location of the storage pits. The calibrated dates of the storage pits were within two hundred years from 8000 to 7800 cal BP. (2) Significant age difference was obtained for terrestrial and marine materials collected from identical horizons. 14C ages of the former were younger by 300–400 yrs than those of the latter. The local reservoir correction, DR, was estimated to be 60 ± 35 14C yr. (3) 14C ages for nut samples suggest that accumulation of Midden No. 1 started at around 8050–7950 cal BP and ended at 7950–7750 cal BP, lasting for ca. 100 cal yr, while accumulation of Midden No. 2 started at around 8050–7800 cal BP and ended at 7800–7650 cal BP, lasting for ca. 200 cal yr. The minor age disagreement probably results from the different locations of the individual middens (Midden No. 1 was formed at a lower level than No. 2). These rather short accumulation periods are consistent with archeological findings that only two types of pottery fragments were unearthed from the shell middens. Kimhae site: (4) A clear 14C age difference was also obtained for terrestrial and marine materials collected from the identical horizons for this site. 14C ages of the former were younger by 300– 400 yrs than those of the latter. The local reservoir correction, DR, was estimated to be 21 ± 34 14C yr from six pairs of terrestrial and marine materials. (5) Formation of the midden at the south wall of Trench 3 started at around the middle of the 1st C cal BC and ended at the middle of the 3rd C cal AD, lasting for ca. 250– 300 cal yr. This time range is coincident with the period of the Proto-Three Kingdoms of Korea (1st C BC to mid-4th C AD), when many agricultural people inhabited the Kimhae region and might have built the shell midden.
T. Nakamura et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 680–687
Acknowledgments The authors would like to thank the members of the Board of Education of Saga city, Japan, and the Foundation of Sanko Institute for Cultural Properties, Korea, for supplying us kindly the excavated samples. This work was supported partly by the ‘‘Grant-in aid for Scientific Research’’ of the Japan Society of the Promotion of Science (JSPS) (subject Nos. 15202023, 16320108 and 22240082). References [1] Saga Municipal Board of Education, The Higashimyo wetland site – the basket maker of the Jomon period around 7000 BP, 2008, p. 12.
687
[2] Saga City Board of Education, Excavation Report of Higashimyo Archeological Site Group-II, No. 6, 2009, p. 328 (in Japanese). [3] A. Matsui, Archaeological Quarterly 113 (2010) 96 (in Japanese). [4] Sanko Institute for Cultural Properties, Excavation Report of Kimhae Heohyeon-ni Site, 2009, p. 458 (in Korean). [5] T. Nakamura, E. Niu, H. Oda, A. Ikeda, M. Minami, T. Ohta, T. Oda, Nucl. Instrum. Methods B223–224 (2004) 124. [6] T. Nakamura, I. Nishida, H. Takada, M. Okuno, M. Minami, H. Oda, Nucl. Instrum. Methods B259 (2007) 453. [7] C. Bronk Ramsey, Radiocarbon 43 (2001) 355. [8] C. Bronk Ramsey, Radiocarbon 51 (2009) 337. [9] P.J. Reimer, M.G.L. Baillie, E. Bard, A. Bayliss, J.W. Beck, P.G. Blackwell, C. Bronk Ramsey, C.E. Buck, G.S. Burr, R.L. Edwards, M. Friedrich, P.M. Grootes, T.P. Guilderson, I. Hajdas, T.J. Heaton, A.G. Hogg, K.A. Hughen, K.F. Kaiser, B. Kromer, F.G. McCormac, S.W. Manning, R.W. Reimer, D.A. Richards, J.R. Southon, S. Talamo, C.S.M. Turney, J. van der Plicht, C.E. Weyhenmeyer, Radiocarbon 51 (2009) 1111. [10] C. Bronk Ramsey, Quaternary Science Reviews 27 (1-2) (2008) 42. [11] M. Stuiver, P.J. Reimer, E. Bard, J.W. Beck, G.S. Burr, K.A. Hughen, F.G. Kromer, J. van der Plicht, M. Spurk, Radiocarbon 40 (3) (1998) 1041.