39Ar dating: a provenance study of Middle Stone Age obsidian artifacts from Ethiopia

Journal of Archaeological Science 33 (2006) 1749e1765 http://www.elsevier.com/locate/jas

Forensic

40

Ar/39Ar dating: a provenance study of Middle Stone Age obsidian artifacts from Ethiopia

Nadia Vogel a,b,*, Sebastien Nomade a,b,1, Agazi Negash c,2, Paul R. Renne a,b b

a Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA Department of Earth and Planetary Science, University of California Berkeley, Berkeley, CA 94720, USA c Laboratory for Human Evolution Studies, University of California Berkeley, Berkeley, CA 94720, USA

Received 16 November 2005; received in revised form 1 March 2006; accepted 16 March 2006

Abstract Obsidian sourcing based on geochemistry is widely applied to reconstruct commerce patterns and dissemination of early hominid groups. Due to problems concerning potential intra-source variability or homogeneity of a geological source over large areas, parameters additional to this classical approach are desirable. Here we present the first 40Ar/39Ar investigation of Middle Stone Age (MSA) obsidian artifacts (i.e. debitage pieces) for this purpose, as well as of potential geological obsidian sources from Ethiopia. With the present pilot study we demonstrate that 40Ar/39Ar geochronology represents a reliable and powerful tool for archaeological provenance studies complementary to the geochemical approach and more recently applied techniques like fission track counting or Mo¨ssbauer spectroscopy. Two independent sets of debitage and potential source rock samples were dated by the 40Ar/39Ar method. Debitage pieces from the Kulkuletti excavation site and obsidian samples from the nearby obsidian outcrop Worja (central Ethiopia) exhibit basically identical age ranges as well as similar Ca/K and Cl/K ratios, supporting the debitage/source rock relationship previously inferred on geochemical grounds. A second small set of geochemically characterized debitage samples from the Porc Epic cave and potential source rocks from an obsidian outcrop at Kone (Eastern Ethiopia) however have different 40 Ar/39Ar ages and Ca/K and Cl/K ratios. These results contradict the previous conclusion about a debitage/source rock relationship of the Porc Epic and Kone samples made on the basis of geochemistry [A. Negash, M.S. Shackley, Archaeometry 48 (2006) 1]. Additional sampling at the Kone outcrop as well as of other obsidian occurrences in the greater area is needed to unambiguously pinpoint the origin of these obsidian tools. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Obsidian; Middle Stone Age;

40

Ar/39Ar dating; Sourcing; Ethiopia; Kulkuletti; Porc Epic

1. Introduction The identification and geographic origin of potential sources for obsidian tools manufactured by Middle Stone Age

* Corresponding author. Institute of Physics, Space Research and Planetary Sciences, Sidlerstrasse 5, University of Berne, 3012 Berne, Switzerland. Tel.: þ41 31 631 4419; fax: þ41 31 631 4405. E-mail address: [email protected] (N. Vogel). 1 Present address: Laboratoire des Sciences du Climat et de l’Environnement, unite´ mixte CEA,CNRS et UVSQ, Orme des Merisiers, 91190, Gif sur Yvette Cedex, France. 2 Present address: Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany. 0305-4403/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jas.2006.03.008

(MSA) hominid groups is of essential importance for reconstructing source utilization, migration patterns, as well as ancient exchange networks. Obsidian sourcing is usually done by searching for matches between the geochemical composition of an obsidian artifact (or an associated debitage piece) and a potential source rock collected from obsidian outcrops [18]. However, such results are not always unambiguous: small-scale geochemical heterogeneities within an obsidian outcrop (e.g., [6]) as well as potential non-uniqueness, i.e. an indistinguishable geochemical composition of obsidian from outcrops over a large area, can hamper this methodology. Thus, additional tools to prove a match between a geological source and an artifact or its debitage are desirable. Previous studies have proposed the use of, e.g., fission track analysis

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

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[2], Mo¨ssbauer spectroscopy [17], or electron paramagnetic resonance [17] as alternative or complementary tools for obsidian sourcing. Fission track densities and ages have been successfully applied to obsidian; however, caution is advised due to the fact that thermal stability of tracks over geological times is rather poor in natural glass and corrections for annealing are always necessary [2]. Somewhat less straightforward is the comparison of Mo¨ssbauer spectra from artifacts and potential geological sources, e.g., due to the difficulty of graphically presenting all Mo¨ssbauer parameters in order to attribute an artifact to a certain geological source [17]. The use of electron paramagnetic resonance is at the moment possible only to a very limited degree, mainly due to the superposition of spectra from para- and ferromagnetic species in glass [17]. It is worth noting that these latter techniques might be sensitive to varying textures in samples with different cooling histories due to collection from different parts of the same flow. Here we propose that 40Ar/39Ar geochronology on artifacts or debitage pieces and potential source rock samples provide easily interpretable and valuable forensic signatures complementary to the conventional geochemical characterization of the samples. Obsidian has been shown to provide internally consistent 40Ar/39Ar data, and has recently been used to constrain the age of early Homo sapiens in the Afar region of Ethiopia [3]. For this study we were provided with two independent sets of debitage/source rock samples, on both of which geochemical analyses have been performed by one of the coauthors

(A.N.; see [10] for the Porc Epic/Kone data set; preliminary data for Kulkuletti/Worja samples, not yet published). The first set of samples encompasses 13 pieces of obsidian tool debitage from an MSA excavation area (Kulkuletti, dated at 181e149 Ka [20]) located west of lake Ziway in central Ethiopia, roughly 100 km south of Addis Ababa (Fig. 1) and nine pieces of potential source rock from a nearby obsidian outcrop. The second set of samples comprises two pieces of MSA debitage from the Porc Epic cave South of Dire Dawa in Eastern Ethiopia and two specimens of potential source rock (picked from a larger selection of potential source rocks taking into account the results of the geochemical analyses published in [10]) from the Kone caldera situated w50 km NE of the town Nazret (Fig. 1). For a schematic overview map of the study areas see also Fig. 1 in [10]. We present 40 Ar/39Ar age data for all of the geochemically characterized MSA debitage pieces and potential source rock samples described above. 2. Geological setting of the excavation sites and source rock outcrops The Kulkuletti excavation site is situated at the eastern slope of the Gademotta ridge roughly 300 m above the Western shore of Lake Ziway in the Central Rift Valley in Ethiopia (Fig. 1). The ridge is built up by a series of Pliocene and Quaternary volcanic rocks intercalated with lacustrine, colluvial,

0

d

Re

Eritrea

150 kilometers

a

Se

Main Ethiopia Rrift and Afar Lake

Dj

ibo

uti

Sudan

Kone Caldera

Dire Dawa

Addis Ababa Kulkuletti/ Worja

Nazret Lake Ziway

Sample location

Gulf of Aden

Somalia

Porc Epic Cave

Galla Lakes Ethiopia

Uganda

Kenya

Fig. 1. Overview map of Ethiopia with locations of the excavation sites Kulkuletti and the Porc Epic Cave as well as the respective potential source rock areas Worja and the Kone Caldera.

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

and alluvial deposits. A detailed description of the rock sequence and the excavation sites can be found in [21]. The debitage samples studied here are from the two sites ETH72-1 and ETH-72-9 at Kulkuletti (Fig. 2 in [21]). Here, certainly due to the vicinity of a suitable source, more than 90% of the excavated tools including flakes and blades were made of obsidian [21]. The potential source rocks

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were collected by one of the coauthors (A.N.) from various positions in an obsidian flow exposed in a road cut in close proximity (a few hundred meters) to the Kulkuletti excavation site (Fig. 1) named ‘‘Worja.’’ The Porc Epic cave, situated in Jurassic limestone [4,13], is located south of the town Dire Dawa (Fig. 1). Tens of thousands of artifacts were excavated, of whichdbesides large

Kulkuletti 3 ETH 72-9-1, B6

1.0

Kulkuletti 5 ETH 72-1, C4

1.0 0.8

Age [Ma]

Age [Ma]

0.8

0.6

0.6

0.4

0.4

Plateau age = 0.630 (0.021) Ma 2σ, neglecting error in J MSWD = 1.5 Includes 38.2% of the 39Ar

0.2

0.2

a 0.0

0.2

0.4

0.6

0.8

0.0

1.0

0.2

Cumulative 39Ar Fraction 1.2 Plateau age = 0.667 (0.068) Ma 2σ, neglecting error in J MSWD = 2.0 Includes 85.9% of the 39Ar

b 0.8

0.8

0.4

Worja 13

Plateau age = 0.672 (0.089) Ma 2σ, neglecting error in J MSWD = 1.09 Includes 45.1% of the 39Ar

0.4

0.0

c 0.0

0.2

0.4

0.6

0.8

d

1.0

0.0

0.2

Cumulative 39Ar Fraction Worja 15

0.6

0.8

1.0

Worja1

1.1

1.0

1.0

Age [Ma]

Age [Ma]

0.4

Cumulative 39Ar Fraction

1.2

0.8 0.6 0.4

0.9 0.8 0.7

Plateau age = 0.764 (0.066) Ma 2σ, neglecting error in J MSWD = 1.2 Includes 70.4% of the 39Ar

0.2

Plateau age = 0.866 (0.020) Ma 2σ, neglecting error in J MSWD = 0.24 Includes 33.5% of the 39Ar

0.6

e 0.0

1.0

0.8

Age [Ma]

Age [Ma]

0.6

Cumulative 39Ar Fraction

Worja 11

1.2

0.4

0.2

0.4

0.6

Cumulative 39Ar Fraction

0.8

1.0

f 0.0

0.2

0.4

0.6

0.8

1.0

Cumulative 39Ar Fraction

Fig. 2. Age spectra of Kulkuletti debitage pieces and Worja source rocks (sorted by ascending ages). Uncertainties of individual age steps as well as of calculated plateau ages are 2s excluding the uncertainty of the irradiation parameter J. Not plotted are age steps with <1% cumulative 39Ar. Plateau steps are colored in gray.

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

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amounts of flint and basaltic tools (w90%)donly a few percent were made from obsidian [4,13,14]. The site is assumed to have been a seasonal hunting camp during MSA times [4] occupied between 77,500 and 61,000 years ago as inferred from obsidian hydration dates [9]. As no tool quality obsidian source is known in the vicinity of the cave, which probably explains the sparsity of obsidian artifacts, Desmond and Clark [4] speculate that the sources for the Porc Epic obsidian artifacts must be located in the southern Afar. Negash and Shackley [10] sampled numerous geological obsidian sources in the greater area and performed geochemical investigations on these rocks as well as on the Porc Epic obsidian artifacts. Based on geochemical similarities, Negash and Shackley [10] proposed that an obsidian flow at Kone, an area that had also been occupied during MSA times, probably represents the source rock for these debitage pieces. The Kone area, also situated in the Central Rift Valley, is one of several Quaternary volcanic centers immediately south of the Afar depression (Fig. 1). The caldera complex is characterized by both silicic (rhyolite, trachyte) and basaltic volcanic products including abundant obsidian flows [5]. A detailed description of the geological setting and the archaeological background for the Porc Epic artifacts/debitage pieces and their potential source rocks has recently been published by Negash and Shackley [10], and Pleurdeau in 2003 [13] and 2005 [14]. The potential source rocks were collected from various locations within an obsidian outcrop close to the NE boundary of the caldera (8
510 4700 N, 39
430 00 E, Fig. 1). 3. Sample preparation Obviously altered surfaces of debitage pieces and source rocks were removed before crushing. The samples were crushed to mm sized pieces in a mortar, and a size fraction 1e0.5 mm was obtained by sieving. From this fraction the clearest pieces, i.e. with only minor inclusions of, e.g., pyroxene, gas bubbles, or devitrified glass were carefully handpicked under alcohol using a binocular microscope. The resulting material (40e140 mg per aliquot) was washed in distilled water before loading roughly 50 mg per aliquot (or the total aliquot) into aluminum disks together with standard minerals for irradiation (for details see, e.g., [16]). 4. Irradiation and the

40

Ar/39Ar analytical method

The 40Ar/39Ar dating method, established by Merrihue and Turner [8] is a variant of the classical KeAr dating technique first established by Aldrich and Nier [1] based on the natural decay at a known rate of the potassium isotope 40K to the argon isotope 40Ar. KeAr dating has the major disadvantage that potassium and argon have to be determined by different techniques, i.e. by wet chemistry and mass spectrometry, respectively. 40 Ar/39Ar dating overcomes this problem by neutron irradiation of a sample. Thereby, a portion of the stable isotope 39K (whose abundance relative to 40K is constant) is transformed to 39Ar via the reaction 39K(n,p)39Ar. This indirectly allows the determination of both the radioactive parent (40K) and the radiogenic

daughter product (40Ar*) by analyzing Ar isotopes only using a noble gas mass spectrometer. To exactly determine the portion of 39K transformed to 39Ar during irradiation, monitor minerals with known ages are co-irradiated with the samples. Excellent reviews on the 40Ar/39Ar dating technique can be found in the literature (e.g., [7,15]). Our sample separates were irradiated in two different irradiations in December 2003 (2 h, irradiation # 316NV) and June 2004 (2.5 h, irradiation # 321NV) at the CLICIT facility of the Oregon State University (OSU) TRIGA reactor. As monitors bracketing the samples we used for both irradiations Alder Creek Sanidine (ACs-2) with an age of 1.193  0.001 Ma [12]. The argon was extracted from the obsidian separates (roughly 20-30 mg each) by stepwise heating with a continuous wave SynradÒ CO2 laser using an expanded beam to assure uniform heating of the samples. After cleaning the resulting gas by admission to SAESÒ getters and a cryogenic condensation trap, the argon isotopic composition was measured in a MAP 215C spectrometer (see, e.g., [12,16] for details on sample loading and Ar analysis). Ar isotopic data corrected for blanks, radioactive decay, and mass discrimination are given in Appendix A, which also contains the neutron fluences (J ) calculated from the ACs-2 monitors using the Steiger and Jaeger decay constants for potassium [19]. Note that the age uncertainties reported here exclude uncertainties in the K decay constants and the absolute age uncertainty of the monitor minerals. The J values (a dimensionless relative measure of the fast neutron fluence) represent average values for each aluminum disk, since no significant variability of J values within one disk were detected. Plateau ages presented in Table 1 are given with 2s uncertainty including the uncertainty of the respective averaged J values. Mass discrimination was constantly monitored by analyzing several air pipettes per day and is generally around 1%/amu favoring the light isotope. In order to correct the data for nucleogenic interferences from K and Ca isotopes we used the following ratios (uncertainties given at 2s level) representing long-term averages from analyses of synthetic Fe-doped KAlSiO4 glass and optical grade CaF2 irradiated at the OSU TRIGA reactor: (38Ar/39Ar)K ¼ 0.0122  5.4  10 5, (40Ar/39Ar)K ¼ 0.0007  0.0006, (38Ar/37Ar)Ca ¼ 1.96  105 1.63  106, (39Ar/ 37 36 37 Ar)Ca ¼ 0.00076  0.00017, ( Ar/ Ar)Ca ¼ 0.000264  1.4  105. To correct the data for atmospheric contribution we used a 40Ar/36Ar ratio of 295.5  0.5 [11]. Backgrounds were analyzed after every three sample steps. The data were corrected using appropriately averaged backgrounds with the respective standard deviations. Typical averaged backgrounds in moles for 40Ar, 39Ar, 38Ar, 37Ar, and 36Ar are (1.29  0.68)  1016, (1.75  2.29)  1018, (5.15  3.09)  1019, 18 (4.55  1.64)  10 , and (1.57  0.69)  1018, respectively. 5. Results 5.1. Age spectra Age spectra and plateau ages for most of the debitage and source rock samples are given in Figs. 2e5. The uncertainties

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765 Table 1 Plateau ages for all samples analyzed for this study. Uncertainties are given at the 2s level including the uncertainty of the respective averaged irradiation parameter (J ) Sample

Age (Ma)



Kulkuletti 1 Kulkuletti 2 Kulkuletti 3 Kulkuletti 4 Kulkuletti 5 Kulkuletti 6 Kulkuletti 7 Kulkuletti 8 Kulkuletti 9 Kulkuletti 10 Kulkuletti 11 Kulkuletti 12 Kulkuletti 13 Worja 1 Worja 2 Worja 3 Worja 11 Worja 12 Worja 13 Worja14 Worja 15 Worja 16 Kone 3 Kone 5 Porc Epic 1 Porc Epic 5

1.287 1.308 No plateau 1.289 0.63 1.302 1.287 1.292 No plateau No plateau 1.252 1.293 1.292 0.866 1.258 No plateau 0.667 1.291 0.672 1.303 0.764 0.06 0.391 0.395 0.266 0.247

0.018 0.018 0.019 0.023 0.019 0.013 0.013

0.012 0.013 0.011 0.021 0.012 0.069 0.028 0.09 0.027 0.068 0.11 0.01 0.008 0.018 0.025

of the plateau ages as well as of the individual age steps of the presented spectra are given at the 2s level (excluding the uncertainties of the J values as they are systematic at that point). Some of the debitage pieces (Kulkuletti 9 and 10) show disturbed spectra with roughly zero age (Appendix A, spectra not shown). Based on these results we assume that the pieces were mixed into the MSA excavation horizon from above and their ages are not discussed any further. Similarly, two of the respective source rock samples with zero ages, Worja 3 and 16, were obviously taken from a modern obsidian flow and are not considered here (Appendix A, spectra not shown). These four samples also differ significantly in chemistry from all other Kulkuletti/Worja samples (see Figs. 6 and 7). Of the remaining Kulkuletti debitage pieces most show ages around 1.29 Ma (Kulkuletti 1, 2, 4, 6, 7, 8, 12, and 13; Figs. 3, 4), one sample has an age of w1.25 Ma (Kulkuletti 11; Fig. 3a), and two samples seem to have ages around 0.6 Ma (Kulkuletti 3 and 5; Fig. 2a,b). In particular Kulkuletti 3 shows a very disturbed spectrum with only the first third of the steps being roughly consistent with each other, but not forming a plateau according to our specifications (i.e., 30% of the cumulative 39ArK; minimum 3 successive steps in agreement with each other within 2s uncertainties). The older samples (>1 Ma) show flat spectra without major visible loss or redistribution of 39ArK. The source rocks collected from the nearby Worja outcrop show a very similar range of ages. Worja 12 and 14 have ages around 1.29 Ma (Figs. 3f,

1753

4e), identical to the major group of the Kulkuletti debitage samples, and Worja 2 with an age of w1.26 Ma (Fig. 3b) is identical to debitage sample Kulkuletti 11 (Fig. 3a). Several samples (Worja 1, 11, 13, 15; Fig. 2cef) have ages between 0.6 and 0.9 Ma, with at least two samples (Worja 13 and 11) being identical within uncertainties with the debitage samples Kulkuletti 3 and 5 (Fig. 2a,b). Note also the very similar shape of the age spectra of the samples Kulkuletti 5 and Worja 13 (see Fig. 2b,d). For the second set of samples the situation is different: both Porc Epic debitage pieces display fairly well behaved spectra with plateau ages of w0.26 Ma (Fig. 5a,b). The two potential Kone source rock samples however show spectra with plateau ages of w0.39 Ma (Fig. 5c,d), about 0.13 Ma older than the debitage samples.

5.2. Air content, Ca/K, and Cl/K ratios As a by-product the Ar analysis also provides information about the proportion of radiogenic and atmospheric 40Ar, and via the 37Ar/39Ar and 38Ar/39Ar ratios proxies for the Ca/K and Cl/K ratios of the samples. Underlying is the fact that during neutron irradiation nearly all 37Ar is produced from Ca via 40Ca(n,a)37Ar anddin terrestrial samplesdbasically all 38Ar is produced by b decay of 38Cl that itself is produced from 37Cl via 37Cl(n,g)38Cl (for details see, e.g., [7]). The percentage of radiogenic 40Ar (% 40Ar*) for each extraction step is given in the appendix. For the Kukuletti/Worja dataset, one findsdnot surprisinglyda nice correlation of the age with the degree of 40Ar* (Appendix A, plot not shown). Whereas a plot of the 37 Ar/39Ar (Ca/K proxy) ratios (Fig. 6) mainly discriminates the two zero age samples Kukuletti 10 and 9 from the rest of the debitage and source rock samples, the 38Ar/39Ar (Cl/ K proxy) ratios (Fig. 7) particularly discriminate the two zero age source rock samples Worja 3 and 16. Also, there is a clear difference between the very low ratios of the older samples (debitage and source rocks) compared to the higher ratios of the samples with ages <1 Ma. Thus, the additional parameters %40Ar*, 37Ar/39Ar, and 38Ar/39Ar do support the debitage/source rock relationship proposed earlier based on the 40 Ar/39Ar ages of the samples and the preliminary geochemical data. For the Porc Epic/Kone data set we find a clear cut difference between the high % 40Ar* of the two debitage pieces (w60e100%) and the two potential source rock samples with low % of 40Ar* (mostly <20%) despite the relative similarity of the ages of the samples. We also find small but distinct differences in the 37Ar/39Ar and 38Ar/39Ar ratios between debitage and source rock samples (Figs. 6, 7). Also, we point out the distinctly different evolution of the 38Ar/39Ar ratios of the Porc Epic debitage samples during gas release compared to the Kone source rocks (Fig. 7, inset). In this case, the additional parameters clearly corroborate the difference in the 40 Ar/39Ar ages between the Porc Epic debitage samples and the Kone potential source rocks.

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

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1.36

Kulkuletti 11 ETH 72-1, D3

Worja 2

1.38 1.34

Age [Ma]

Age [Ma]

1.32

1.28

1.26 1.22

1.24

1.18

Plateau age = 1.2523 (0.0056) Ma 2σ, neglecting error in J MSWD = 1.2 Includes 68.2% of the 39Ar

1.20

0.0

1.30

0.4

0.2

0.6

Plateau age = 1.2584 (0.0064) Ma 2σ, neglecting error in J MSWD = 1.3 Includes 62.4% of the 39Arr

1.14

a 0.8

b

1.0

0.0

0.4

0.2

Cumulative 39Ar Fraction

0.6

0.8

1.0

Cumulative 39Ar Fraction

Kulkuletti 1 ETH 72-9-1, B6

Kulkuletti 7 ETH 72-9-1, B8

1.38 1.4

Age [Ma]

Age [Ma]

1.34

1.3

1.30

1.26 1.2

0.0

Plateau age = 1.2865 (0.0053) Ma 2σ, neglecting error in J MSWD = 0.94 Includes 71.5% of the 39Ar

0.2

0.4

0.6

Plateau age = 1.2873 (0.0057) Ma 2σ, neglecting error in J MSWD = 1.16 Includes 71.1% of the 39Ar

1.22

c 0.8

1.0

0.0

0.2

0.6

d 0.8

1.0

Cumulative 39Ar Fraction

Cumulative 39Ar Fraction

1.8

0.4

Kulkuletti 4 ETH 72-1, C4

Worja 12

1.8 1.6

Age [Ma]

Age [Ma]

1.6 1.4

1.2

1.2 Plateau age = 1.2891 (0.0082) Ma 2σ, neglecting error in J MSWD = 1.04 Includes 91.8% of the 39Ar

1.0

0.0

1.4

0.2

0.4

0.6

Plateau age = 1.291 (0.014) Ma 2σ, neglecting error in J MSWD = 0.87 Includes 96% of the 39Ar

1.0

e 0.8

1.0

Cumulative 39Ar Fraction

f 0.0

0.2

0.4

0.6

0.8

1.0

Cumulative 39Ar Fraction

Fig. 3. Age spectra of Kulkuletti debitage pieces and Worja source rocks (sorted by ascending ages). Uncertainties of individual age steps as well as of calculated plateau ages are 2s excluding the uncertainty of the irradiation parameter J. Not plotted are age steps with <1% cumulative 39Ar. Plateau steps are colored in gray.

6. Discussion The preliminary geochemical data for all Kulkuletti/Worja samples (except for the four ‘‘zero-age’’ samples) had been sufficiently uniform to propose a debitage/source rock relationship. The argon data not only support the preliminary geochemical results but provide further detailed evidence for this

relationship: Despite uniform geochemistry, the ages of the debitage pieces fall into three different groups of w1.3, 1.25, and 0.6 Ma, indicating that the raw material for tool production had been collected from different localities or flows either from within one outcrop or from different outcrops altogether. The magmatic source for the obsidian flows must have been chemically homogeneous over time (between

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

Kulkuletti 13 ETH 72-1, D3

1755

Kulkuletti 8 ETH 72-9-1, B8

1.4

1.32

Age [Ma]

Age [Ma]

1.36

1.28

1.3

1.2 Plateau age = 1.2924 (0.0047) Ma 2σ, neglecting error in J MSWD = 0.98 Includes 97.7% of the 39Ar

1.24

0.2

0.0

0.4

0.6

Plateau age = 1.2922 (0.0058) Ma 2σ, neglecting error in J MSWD = 0.87 Includes 100% of the 39Ar

a 0.8

1.0

0.0

0.2

Cumulative 39Ar Fraction

0.4

0.6

b 0.8

1.0

Cumulative 39Ar Fraction

Kulkuletti 12 ETH 72-1, D3

1.44

Kulkuletti 6 ETH 72-1, C4

1.38 1.40

Age [Ma]

Age [Ma]

1.34

1.30

1.26

1.36 1.32 1.28

Plateau age = 1.2931 (0.0057) Ma 2σ, neglecting error in J MSWD = 1.6 Includes 80.7% of the 39Ar

1.22

0.0

0.2

0.4

0.6

Plateau age = 1.3020 (0.0069) Ma 2σ, neglecting error in J MSWD = 0.52 Includes 100% of the 39Ar

1.24

c 0.8

0.0

1.0

0.2

0.6

d 1.0

0.8

Cumulative 39Ar Fraction

Cumulative 39Ar Fraction

1.5

0.4

Worja 14

1.42

Kulkuletti 2 ETH 72-9-1, B6

1.4 1.3

Age [Ma]

Age [Ma]

1.38

1.2 1.1

1.30 1.26

Plateau age = 1.303 (0.011) Ma 2σ, neglecting error in J MSWD = 0.27 Includes 86.3% of the 39Ar

1.0

0.0

1.34

0.2

0.4

0.6

Plateau age = 1.3076 (0.0043) Ma 2σ, neglecting error in J MSWD = 1.06 Includes 87.4% of the 39Ar

1.22

e 0.8

1.0

Cumulative 39Ar Fraction

0.0

0.2

0.4

0.6

f 0.8

1.0

Cumulative 39Ar Fraction

Fig. 4. Age spectra of Kulkuletti debitage pieces and Worja source rocks (sorted by ascending ages). Uncertainties of individual age steps as well as of calculated plateau ages are 2s excluding the uncertainty of the irradiation parameter J. Not plotted are age steps with <1% cumulative 39Ar. Plateau steps are colored in gray.

1.3 Ma and 0.6 Ma) and maybe also spatially, if the raw material was taken from different outcrops. The 40Ar/39Ar ages found for the potential source rocks from an outcrop close to the excavation site show an amazing agreement with the age range of the debitage pieces (Fig. 8). Also here, obsidian samples dating at 1.3 Ma and 1.25 Ma were found, as well as samples identical to the 0.6 Ma debitage

pieces within uncertainties. Moreover, not only the ages, but also the shapes of the spectra from debitage and potential source rock samples are fairly similar (compare, e.g., Kulkuletti 3, 5 and Worja 11, 13 in Fig. 2), further corroborating the source rock-debitage relationship. Thus it is clear that the rocks from which the tools were made were indeed likely collected from the same outcrop from which our potential source rocks were

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

1756 Porc Epic 1

0.7 0.6

Plateau age = 0.247 (0.025) Ma 2σ, neglecting error in J MSWD = 1.09 Includes 100% of the 39Ar

0.4

0.5

0.3

Age [Ma]

Age [Ma]

Porc Epic 5 Plateau age = 0.266 (0.017) Ma 2σ, neglecting error in J MSWD = 1.7 Includes 88% of the 39Ar

0.4 0.3

0.2

0.2 0.1 0.1

a 0.0

0.2

0.4

0.6

b 1.0

0.8

0.0

0.2

0.4

Cumulative 39Ar Fraction

0.6

1.0

0.8

Cumulative 39Ar Fraction

Kone 3

0.7

Kone 5

0.6 0.6

Age [Ma]

Age [Ma]

0.5

0.4

0.3

0.5 0.4 0.3

Plateau age = 0.3912 (0.0018) Ma 2σ, neglecting error in J MSWD = 1.8 Includes 68.6% of the 39Ar

0.2

Plateau age = 0.3950 (0.0057) Ma 2σ, neglecting error in J MSWD = 1.82 Includes 92% of the 39Ar

0.2

c 0.0

0.2

0.4

0.6

0.8

d 0.0

1.0

0.4

0.2

Cumulative 39Ar Fraction

0.6

1.0

0.8

Cumulative 39Ar Fraction

Fig. 5. Age spectra of Porc Epic debitage pieces and Kone source rocks (sorted by ascending ages). Uncertainties of individual age steps as well as of calculated plateau ages are 2s excluding the uncertainty of the irradiation parameter J. Not plotted are age steps with <1% cumulative 39Ar. Plateau steps are colored in gray.

0.038

PE1

0.036

Kulkuletti debitage Worja potential source rocks Porc Epic debitage Kone potential source rocks

PE5 Ko5

0.034

Ko3

0.032 37Ar/39Ar

taken. Since the Kulkuletti debitage pieces from both excavation sites (ETH 72-1, ETH 72-9-1) span the same age range (0.6e1.3 Ma), it is thinkable that ETH 72-1, lying downhill from ETH 72-9-1 (see Fig. 2 in [20]), contains mainly reworked material from ETH 72-1. On the other hand, if both excavation sites represent individual cultural horizons it can be inferred that the MSA hominids living during both periods used the same tool quality obsidian flows of the nearby Worja outcrop. The second small data set was obtained from two Porc Epic debitage and two Kone potential source rock samples whose geochemical signatures were homogeneous enough to propose a debitage/source rock relationship [10]. In contrast to the Kulkuletti/Worja samples, however, the 40Ar/39Ar data do not support this conclusion. The raw material for the obsidian tools was taken from an obsidian flow with an age of 0.26 Ma, while the potential source material displays a distinctly higher age of 0.39 Ma (Fig. 9). Although it is still possible that the source rocks for the studied Porc Epic debitage samples reside somewhere close to the 0.39 Ma old obsidian flow that was sampled for this study, further evidence to deduce a debitage/source rock relationship is necessary. This is true in particular because the greater Porc Epic/Kone area hosts several as yet unstudied obsidian outcrops

0.030 0.028

K9 K10

0.026

K1 K2 K4 K6

0.024 0.022 0.020

K5

W3

K3

W1

0.018 0.0

0.2

0.4

0.6

W2

W15

W11 W13

W16

0.8

K7 K8 K11 K12 K13

W14 W12

1.0

1.2

1.4

Age [Ma] Fig. 6. 37Ar/39Ar ratios vs. ages of debitage pieces and potential source rocks. The 37Ar/39Ar ratios represent proxies for the Ca/K ratios of the samples. The plot clearly discriminates the two zero age debitage samples Kulkuletti 9 and Kulkuletti 10 from all other Kulkuletti/Worja samples. Smaller differences are visible between the Porc Epic debitage and the Kone source rock samples.

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765 0.42

Kulkuletti debitage Worja potential source rocks Porc Epic debitage Kone potential source rocks

0.40

W3

0.019

Ar/39Ar

0.040

38

0.035

0.38

0.018

0.36

0.017

steps W16 K5 K3

0.020 PE5 PE1

K10

0.015

0.0

0.2

0.4

W13 W15 W1

W11

Ko3 Ko5

K9

K1 K2 K4 K6 K7

K8 K11 K12 K13

0.8

1.0

1.2

0.32 0.30 0.28 0.26

W2 W12 W14

0.6

Age [Ma]

0.34 1 2 3 4 5 6 7 8 9 10 11 12 13 14

38Ar/39Ar

0.016

0.030 0.025

1.4

0.24 Porc Epic debitage Kone potential source rocks

0.22

Age [Ma]

ic

Fig. 7. 38Ar/39Ar ratios vs. ages of debitage pieces and potential source rocks. The 38Ar/39Ar ratios represent proxies of the Cl/K ratios of the samples. The inset shows the evolution of the 38Ar/39Ar ratios over the individual extraction steps of the Porc Epic debitage and Kone potential source rock samples. The plot clearly discriminates the two zero age source rocks Worja 3 and Worja 16 from all other Kulkuletti/Worja samples. The small differences of the 38 Ar/39Ar ratios of the Porc Epic debitage and the Kone source rock samples are corroborated by the different evolution of the ratios during stepwise gas release (inset).

(see, e.g., Fig. 6 in [13]) that may or may not have been reasonable candidates for potential sources of obsidian during the MSA. Thus, more sampling in this area would be of great value. 7. Conclusion and outlook Obsidian sourcing is a powerful tool for reconstructing source utilization, migration, and exchange networks of MSA

1.34 1.32 1.30

Age [Ma]

1.28 1.26 1.24 1.22 1.20 0.8

1757

Kulkuletti debitage Worja potential source rock

0.6 0.4 3 i 5 11 13 15 1 11 2 i 1 i 7 i 4 12 13 i 8 12 i 6 14 i 2 ti t rja tti rja ett ett ett ja tti ett tti ett ja ett et et ja ja ja ul kul or or or Wo ule Wo kul kul kul or ule kul ule kul or kul k l l l l l W W W W lk ul lk ul W ul lk Ku Ku K Ku K Ku Ku Ku K Ku Ku

Fig. 8. Comparison of plateau ages from Kulkuletti debitage pieces (black symbols) and obsidian samples from the potential source Worja (gray symbols) sorted by ascending ages. Age uncertainties are at the 2s level including the uncertainty of the respective irradiation parameter (J ).

rc

Po

1

ic

Ep

rc

Po

Ep

5

e

n Ko

3

e

5

n Ko

Fig. 9. Comparison of plateau ages from Porc Epic debitage pieces (black symbols) and obsidian samples from the potential source Kone (gray symbols). Age uncertainties are at the 2s level including the uncertainty of the respective irradiation parameter (J ).

hominid groups. In addition to the geochemical characterization of artifacts/debitage and potential geological sources we propose that radioisotopic ages, age spectra, and Ar isotope ratios obtained by 40Ar/39Ar dating are reliable forensic tools to unambiguously identify potential debitage/source rock relationships. This is especially important since obsidian can display large chemical intra-source heterogeneities (e.g., [6]) or can have homogeneous compositions over large distances and/or time spans. Based on preliminary geochemical signatures the obsidian outcrop Worja had been suggested as being the source for the studied obsidian tools from the Kulkuletti MSA excavation site. Our 40Ar/39Ar ages from various locations within the Worja outcrop perfectly cover the range of ages (between 1.3 and 0.6 Ma) of the debitage pieces from the two Kulkuletti excavation sites ETH 71-1 and ETH 72-9, thus confirming the results of the geochemical sourcing. In the case of Worja, the 40 Ar/39Ar data even seem to allow the identification of the individual obsidian layers/flows from which the raw material for tool production had been taken by the MSA inhabitants of Kulkuletti. Furthermore, if the lower site ETH 72-1 does not only contain reworked artifacts from the uphill site, the same locality was exploited over at least several 10,000s of years, as inferred from age determinations of volcanic layers below and in between the two excavation sites ETH 72-1 and ETH 72-9 [20,21]). This implies a transfer of knowledge about the tool quality obsidian flows and sources over generations. The two debitage samples from the MSA excavation site Porc Epic, however, have distinctly younger ages (0.26 Ma) than the proposed (based on geochemical grounds) source rocks from Kone (0.4 Ma). This excludes the sampled layers of the Kone outcrop as the geological source for the studied artifacts/debitage pieces. Additional sampling in the Kone volcanic field and other volcanic centers in the neighborhood are

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

1758

data of potential obsidian tool sources would be a great asset for the archaeological community.

necessary to identify the source for the Porc Epic artifacts, in particular since several obsidian outcrops between Porc Epic and Kone have not yet been investigated geochemically at all. We have shown with this pilot study the potential for archaeology research of 40Ar/39Ar dating of obsidian debitage and geological sources in combination with geochemical analyses. Not only the ages of the samples, but also the age range of a set of samples, the shape of the spectra, as well as the percentage of 40Ar*, 37Ar/39Ar, and 38Ar/39Ar ratios represent valuable parameters in order to determine geological sources for MSA obsidian tools. The technique can (and should!) be extended to all tool quality obsidian outcrops in the EastAfrican rift area but also to other regions in the world where geochemical obsidian sourcing and/or hydration dating has been or will be applied in order to reconstruct socioeconomic interactions of early hominid groups. In the future a global database including both chemistry and argon geochronology

Acknowledgments We would like to thank the Authority for Research and Conservation of Cultural Heritage of Ethiopia for providing debitage pieces used for this study. We thank T.D. White for suggesting this project, M.S. Shackley for helpful discussions, and J.A. Whitby for an informal review. We also like to thank two anonymous reviewers for their helpful comments and suggestions. Geochemical analyses were performed by A.N. at the XRF Laboratory of the Department of Anthropology, University of Berkeley, California. A.N. would like to thank the L.S.B. Leakey Foundation for financial support of the fieldwork. The work of N.V., S.N. and P.R.R. was supported by the Ann and Gordon Getty Foundation.

Appendix A Full Ar data corrected for decay, blank, and mass discrimination Steps

Power (W)

36

Ar



37

Ar



38

Ar



39

Ar



40

Ar



%40Ar*

Age (Ma)

wo J

6

Kulkuletti 1 [ETH 72-9-1, exc. unit A 1 0.001 B 1.5 0.003 C 2 0.009 D 2.5 0.021 E 3 0.023 F 4 0.058 G 5 0.131 H 5.5 0.073 I 6.3 0.104 J 7.5 0.180 K 9.2 0.162 L 11 0.177 M 13 0.155 N 15.5 0.176 O 18 0.098 P 30 0.093

B6], Irradiation 316 0.002 0.00 0.002 0.03 0.002 0.11 0.002 0.28 0.002 0.36 0.002 0.99 0.002 2.25 0.002 1.36 0.002 1.77 0.003 2.61 0.002 2.78 0.002 2.92 0.002 2.51 0.002 2.88 0.002 1.49 0.002 1.59

NV-A, J ¼ 0.00053  3.6  10 0.01 0.000 0.002 0.11 0.01 0.017 0.002 0.95 0.01 0.075 0.004 4.83 0.01 0.198 0.004 13.55 0.01 0.251 0.005 16.86 0.01 0.676 0.006 47.31 0.03 1.618 0.016 107.16 0.02 0.941 0.007 64.27 0.02 1.274 0.009 87.92 0.02 1.840 0.008 125.75 0.02 1.926 0.009 131.11 0.02 2.045 0.009 141.14 0.02 1.782 0.010 123.64 0.03 2.018 0.018 135.92 0.01 1.071 0.008 74.39 0.02 1.098 0.009 77.18

0.02 0.02 0.04 0.06 0.07 0.09 0.21 0.10 0.18 0.25 0.23 0.16 0.16 0.15 0.19 0.22

0.5 1.9 8.6 23.3 29.2 80.4 182.6 110.9 147.8 222.9 224.4 242.7 213.4 233.9 128.7 133.1

0.2 0.2 0.2 0.2 0.3 0.3 0.5 0.4 0.5 0.6 0.6 0.5 0.5 0.4 0.5 0.5

133.0 54.8 69.5 74.0 76.8 78.8 78.8 80.6 79.3 76.2 78.7 78.5 78.6 77.9 77.6 79.3

5.41 1.05 1.18 1.21 1.27 1.28 1.28 1.33 1.27 1.29 1.29 1.29 1.29 1.28 1.28 1.31

4.70 0.61 0.14 0.05 0.04 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01

Kulkuletti 2 [ETH 72-9-1, exc. unit A 1.5 0.004 B 2 0.003 C 2.5 0.002 D 3 0.002 E 3.5 0.002 F 4.5 0.007 G 5.5 0.069 H 6.2 0.010 I 7 0.007 J 8 0.016 K 9.5 0.011 L 11.5 0.007 M 14 0.009 N 16.5 0.007 O 19 0.001 P 30 0.005

B6], Irradiation 316 0.002 0.01 0.002 0.08 0.002 0.23 0.002 0.34 0.002 0.67 0.002 1.18 0.002 1.84 0.002 1.76 0.002 2.00 0.002 2.34 0.002 3.16 0.002 2.98 0.002 3.43 0.002 2.34 0.002 1.34 0.002 1.80

NV-A, J ¼ 0.00053  3.6  106 0.01 0.010 0.004 0.68 0.01 0.061 0.003 4.05 0.01 0.138 0.004 10.43 0.01 0.249 0.004 17.02 0.01 0.452 0.006 32.09 0.02 0.789 0.014 53.58 0.02 1.306 0.007 91.05 0.02 1.246 0.009 86.76 0.03 1.325 0.010 94.35 0.03 1.568 0.010 109.82 0.03 2.142 0.010 148.60 0.02 2.042 0.012 143.34 0.02 2.362 0.012 167.16 0.03 1.584 0.011 111.89 0.02 0.926 0.007 64.47 0.02 1.252 0.010 87.71

0.02 0.04 0.05 0.06 0.07 0.11 0.11 0.19 0.19 0.20 0.23 0.17 0.13 0.21 0.12 0.20

1.5 6.1 15.0 24.2 45.2 74.3 144.0 120.8 132.1 154.2 206.9 198.0 231.2 156.2 90.0 123.1

0.3 0.2 0.2 0.2 0.2 0.3 0.3 0.4 0.4 0.4 0.5 0.4 0.4 0.4 0.3 0.4

28.6 84.3 97.1 98.2 98.7 97.3 85.9 97.7 98.5 97.0 98.5 99.1 99.0 98.8 100.5 99.0

0.59 1.21 1.34 1.34 1.33 1.29 1.30 1.30 1.32 1.30 1.31 1.31 1.31 1.32 1.34 1.33

1.12 0.17 0.07 0.04 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.01 0.01 0.01

Kulkuletti A B C D E

B6], Irradiation 316 0.003 0.03 0.003 0.10 0.003 0.20 0.003 0.32 0.004 0.36

NV-A, J ¼ 0.00053  3.6  106 0.01 0.044 0.003 1.78 0.01 0.107 0.003 5.11 0.01 0.194 0.004 9.91 0.01 0.322 0.004 16.35 0.01 0.383 0.005 19.49

0.02 0.03 0.04 0.05 0.06

21.9 60.0 92.5 152.8 183.6

0.4 0.5 0.5 0.6 0.7

9.1 4.5 5.8 6.2 4.6

1.07 0.50 0.52 0.55 0.42

0.42 0.14 0.08 0.06 0.05

3 [ETH 72-9-1, exc. unit 1.5 0.067 2 0.194 2.5 0.294 3 0.485 3.5 0.592

(continued on next page)

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

1759

Appendix A (continued) 36

0.004 0.004 0.005 0.004 0.005 0.005 0.004 0.004 0.004 0.003 0.003

0.8 0.9 1.0 0.8 1.1 0.9 0.7 0.7 0.8 0.5 0.6

6.1 6.6 6.1 7.4 5.7 6.0 7.4 10.9 15.8 16.9 11.3

0.54 0.59 0.58 0.68 0.59 0.62 0.69 0.86 1.08 1.07 0.89

0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.02 0.03 0.05 0.04

Kulkuletti 4 [ETH 72-1, exc. unit C4], Irradiation 316 NV-A, J ¼ 0.00053  3.6  106 A 1.5 0.001 0.000 0.00 0.00 0.001 0.000 0.09 B 2 0.000 0.002 0.12 0.01 0.091 0.003 6.10 C 2.5 0.001 0.002 0.18 0.01 0.127 0.004 9.00 D 3 0.010 0.003 0.37 0.01 0.274 0.005 19.55 E 3.5 0.011 0.002 0.43 0.01 0.334 0.005 22.30 F 4.5 0.021 0.002 0.84 0.02 0.607 0.008 40.65 G 5.5 0.032 0.002 1.14 0.02 0.798 0.006 55.63 H 6.2 0.030 0.002 1.05 0.01 0.768 0.007 52.92 I 7 0.039 0.002 1.49 0.01 1.093 0.008 75.32 J 8 0.022 0.002 1.05 0.02 0.699 0.006 48.34 K 9.5 0.034 0.002 1.17 0.02 0.783 0.006 53.50 L 11.5 0.039 0.002 1.47 0.02 1.023 0.007 71.50 M 14 0.023 0.002 1.39 0.02 0.971 0.008 67.51 N 16.5 0.012 0.002 0.74 0.01 0.511 0.006 35.92 O 22 0.017 0.002 0.45 0.01 0.307 0.004 21.77 P 30 0.008 0.002 0.42 0.01 0.309 0.005 21.29

0.00 0.04 0.05 0.08 0.06 0.10 0.11 0.10 0.18 0.10 0.11 0.18 0.12 0.08 0.06 0.07

0.5 9.9 13.6 29.7 33.9 60.9 83.9 80.7 112.9 71.2 80.8 108.2 99.0 52.6 35.9 32.6

0.0 0.2 0.2 0.3 0.2 0.3 0.3 0.3 0.4 0.3 0.3 0.4 0.3 0.3 0.2 0.2

62.0 100.9 98.7 90.3 90.3 89.7 88.7 89.1 89.8 90.9 87.8 89.3 93.2 93.3 86.4 92.4

3.47 1.56 1.42 1.31 1.31 1.28 1.28 1.30 1.29 1.28 1.27 1.29 1.31 1.30 1.36 1.35

0.60 0.11 0.08 0.04 0.03 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.03 0.03

Kulkuletti 5 [ETH 72-1, exc. unit C4], Irradiation 316 NV-A, J ¼ 0.00053  3.6  106 A 2 0.214 0.003 0.14 0.01 0.146 0.003 6.85 B 3 0.862 0.004 0.59 0.01 0.591 0.006 30.04 C 4 1.590 0.005 1.09 0.01 1.092 0.008 56.11 D 5 1.756 0.005 1.26 0.01 1.221 0.007 62.33 E 6.5 3.240 0.007 2.10 0.02 2.054 0.012 102.85 F 7.5 3.174 0.007 1.85 0.01 1.865 0.010 89.79 G 8.5 3.056 0.007 1.66 0.02 1.705 0.010 78.89 H 9.5 1.903 0.005 1.23 0.02 1.211 0.007 60.42 I 11.5 2.728 0.006 1.98 0.03 1.827 0.009 94.19 J 13 1.638 0.005 1.16 0.02 1.107 0.008 54.94 K 15 1.187 0.004 0.86 0.02 0.781 0.008 39.87 L 18 1.114 0.004 0.69 0.01 0.660 0.007 33.68 M 22 0.468 0.003 0.40 0.02 0.336 0.005 17.64 N 30 0.711 0.004 0.49 0.02 0.425 0.006 21.15

0.03 0.07 0.07 0.08 0.13 0.13 0.11 0.08 0.13 0.10 0.09 0.07 0.05 0.07

65.7 268.3 500.3 552.5 996.4 971.2 938.6 600.4 872.0 521.5 377.7 351.1 155.1 228.0

0.4 0.8 0.8 0.9 1.6 1.6 1.6 0.9 1.4 1.1 0.9 0.9 0.5 0.8

3.4 4.9 6.0 5.9 3.8 3.3 3.7 6.2 7.4 7.1 7.0 6.1 10.7 7.8

0.32 0.42 0.51 0.50 0.35 0.34 0.42 0.59 0.66 0.64 0.63 0.60 0.90 0.80

0.11 0.04 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.03 0.03 0.05 0.05

Kulkuletti 6 [ETH 72-1, exc. unit C4], Irradiation 316 NV-A, J ¼ 0.00053  3.6  106 A 2 0.001 0.002 0.15 0.01 0.103 0.004 6.83 B 3 0.004 0.002 0.46 0.01 0.360 0.005 25.04 C 4 0.003 0.002 0.76 0.02 0.554 0.005 39.08 D 5 0.007 0.002 1.33 0.02 0.983 0.007 67.72 E 6.5 0.010 0.002 1.68 0.03 1.153 0.007 81.61 F 7.5 0.006 0.002 1.52 0.03 0.991 0.007 69.04 G 8.5 0.004 0.002 1.49 0.02 0.959 0.008 66.93 H 9.5 0.005 0.002 1.49 0.02 0.961 0.008 68.10 I 11.5 0.005 0.002 1.59 0.02 1.044 0.010 73.72 J 13 0.004 0.002 1.50 0.03 0.964 0.008 70.19 K 15 0.003 0.002 0.88 0.01 0.599 0.005 41.74 L 18 0.003 0.002 0.74 0.01 0.524 0.005 35.40 M 22 0.001 0.002 0.47 0.01 0.325 0.005 24.15 N 30 0.001 0.002 0.43 0.02 0.293 0.004 20.34

0.02 0.07 0.10 0.14 0.19 0.15 0.10 0.11 0.19 0.12 0.09 0.08 0.06 0.07

10.1 35.5 54.3 93.8 114.2 95.6 92.0 93.6 102.1 96.6 57.8 49.5 33.8 28.8

0.2 0.2 0.3 0.3 0.4 0.4 0.3 0.3 0.4 0.4 0.3 0.2 0.2 0.2

97.3 97.0 98.3 98.1 97.4 98.1 98.9 98.7 98.6 98.9 98.7 98.3 101.4 98.6

1.38 1.31 1.31 1.30 1.30 1.30 1.30 1.30 1.30 1.30 1.30 1.31 1.36 1.33

0.10 0.03 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.03 0.03

NV-B, J ¼ 0.00053  2.3  106 0.01 0.062 0.003 4.53 0.01 0.410 0.004 27.97 0.02 0.588 0.007 39.47

0.04 0.07 0.10

7.8 46.2 64.5

0.2 0.2 0.3

75.3 82.2 82.4

1.24 1.30 1.29

0.15 0.02 0.02

7 [ETH 72-9-1, exc. unit 2 0.007 3 0.028 4 0.039

0.75 1.05 0.93 0.96 1.00 0.92 0.94 0.96 0.72 0.32 0.47

0.01 0.02 0.01 0.01 0.02 0.02 0.03 0.01 0.01 0.01 0.01

B8], Irradiation 316 0.002 0.10 0.002 0.52 0.002 0.82

Ar



0.771 0.987 0.922 0.889 0.949 0.855 0.887 0.933 0.637 0.286 0.441

0.006 0.007 0.008 0.007 0.006 0.006 0.007 0.009 0.006 0.004 0.006

Ar



%40Ar*

360.6 463.5 461.2 439.5 497.1 446.3 442.6 405.9 256.0 105.3 194.2

Kulkuletti A B C

1.143 1.463 1.464 1.375 1.583 1.417 1.385 1.222 0.728 0.296 0.582



40

0.07 0.06 0.09 0.07 0.09 0.07 0.06 0.06 0.10 0.06 0.06

4.5 5.5 6.2 7 8 9.5 11.5 14 16.5 19 30

Ar

39

39.40 49.97 45.85 45.54 46.41 41.16 45.13 49.03 35.83 15.85 23.54

F G H I J K L M N O P



38



Power (W)

Ar

37

Ar

Steps

Age (Ma)

wo J

(continued on next page)

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

1760 Appendix A (continued)

Ar



39



0.782 1.394 1.838 1.850 2.703 1.923 0.701 0.504

0.007 0.013 0.011 0.010 0.011 0.009 0.006 0.005

54.88 95.56 125.97 127.69 188.34 133.39 49.62 35.88

0.10 0.21 0.25 0.24 0.19 0.14 0.09 0.09

88.7 162.6 203.1 208.1 301.5 211.3 75.3 54.1

0.4 0.5 0.5 0.6 0.5 0.5 0.3 0.3

82.1 77.9 83.4 82.0 84.4 85.4 89.3 93.2

1.27 1.27 1.28 1.28 1.29 1.29 1.29 1.34

0.01 0.01 0.01 0.01 0.00 0.01 0.01 0.02

NV-B, J ¼ 0.00053  2.3  106 0.01 0.114 0.003 7.78 0.01 0.274 0.004 17.53 0.01 0.544 0.005 36.72 0.02 0.729 0.006 50.60 0.02 1.435 0.010 100.21 0.02 1.356 0.008 95.24 0.03 1.262 0.009 88.65 0.02 0.928 0.007 65.09 0.02 1.130 0.008 80.15 0.03 1.509 0.008 105.25 0.02 1.057 0.008 74.16 0.03 1.035 0.007 72.13 0.01 0.555 0.005 38.51 0.02 0.461 0.006 33.06

0.05 0.06 0.09 0.09 0.22 0.18 0.19 0.13 0.17 0.18 0.18 0.20 0.10 0.09

11.2 24.7 50.6 69.4 137.6 133.4 121.1 88.7 110.0 144.9 101.6 99.2 52.8 45.3

0.2 0.2 0.3 0.3 0.5 0.4 0.4 0.3 0.4 0.4 0.4 0.4 0.3 0.3

106.9 91.3 99.9 99.5 98.1 96.6 98.3 99.2 98.0 98.3 99.1 99.4 99.3 100.2

1.48 1.23 1.32 1.30 1.29 1.29 1.28 1.29 1.28 1.29 1.30 1.31 1.30 1.31

0.09 0.04 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02

Kulkuletti 9 [ETH 72-1, exc. unit A5], Irradiation 316 NV-B, J ¼ 0.00053  2.3  106 A 2 0.279 0.003 0.14 0.01 0.141 0.004 5.88 B 3 0.044 0.002 0.98 0.01 0.552 0.008 35.28 C 4 0.071 0.002 1.56 0.02 0.892 0.008 57.22 D 5 0.096 0.002 1.65 0.03 0.947 0.010 60.78 E 6.5 0.204 0.003 2.98 0.03 1.621 0.010 104.12 F 7.5 0.314 0.003 4.16 0.04 2.325 0.014 150.44 G 8.5 0.107 0.002 2.58 0.04 1.395 0.008 89.67 H 10 0.091 0.002 2.15 0.03 1.218 0.010 78.93 I 13 0.129 0.002 3.05 0.04 1.736 0.012 112.31 J 15 0.094 0.002 2.56 0.03 1.495 0.009 96.42 K 18 0.065 0.002 1.74 0.03 0.999 0.010 65.42 L 23 0.065 0.002 1.48 0.01 0.860 0.008 55.28 M 30 0.099 0.002 2.06 0.02 1.200 0.009 78.37

0.03 0.08 0.14 0.11 0.17 0.24 0.20 0.20 0.22 0.18 0.12 0.11 0.22

82.8 14.0 21.9 30.1 60.0 88.3 31.9 26.5 38.4 31.0 20.7 20.9 30.4

0.5 0.2 0.2 0.2 0.3 0.3 0.2 0.2 0.2 0.2 0.2 0.2 0.2

0.2 6.1 5.1 6.4 0.6 5.0 0.8 0.6 1.3 10.8 7.5 7.9 3.9

0.02 0.02 0.02 0.03 0.00 0.03 0.00 0.00 0.00 0.03 0.02 0.03 0.01

0.13 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01

Kulkuletti 10 [ETH 72-1, exc. unit A5], Irradiation 316 A 2 0.040 0.002 0.11 B 3 0.256 0.003 0.78 C 4 0.469 0.003 1.34 D 5 0.668 0.003 1.96 E 6.5 1.902 0.006 3.12 F 7.5 1.862 0.006 3.17 G 8.5 1.158 0.004 2.54 H 9.5 0.581 0.003 2.32 I 11.5 0.683 0.003 3.00 J 13 0.458 0.003 1.99 K 15 0.345 0.003 1.06 L 18 0.247 0.003 1.24 M 22 0.350 0.003 1.16 N 30 0.616 0.003 1.60

NV-B, J ¼ 0.00053  2.3  106 0.01 0.074 0.003 4.36 0.02 0.470 0.006 28.17 0.02 0.864 0.007 50.12 0.02 1.209 0.008 71.24 0.02 2.090 0.009 115.23 0.04 2.077 0.011 113.36 0.03 1.636 0.008 92.57 0.03 1.403 0.007 83.68 0.04 1.734 0.009 106.71 0.02 1.240 0.009 74.66 0.01 0.682 0.005 40.88 0.02 0.736 0.006 44.96 0.02 0.720 0.006 42.73 0.03 1.013 0.009 58.31

0.02 0.08 0.09 0.10 0.24 0.25 0.13 0.17 0.24 0.15 0.08 0.10 0.10 0.10

11.3 71.8 131.5 187.7 538.2 527.4 330.2 167.4 199.5 133.3 101.0 71.6 104.6 179.1

0.2 0.3 0.4 0.5 1.2 1.3 0.6 0.5 0.6 0.4 0.4 0.3 0.4 0.5

5.4 5.4 5.5 5.4 4.6 4.5 3.8 2.7 1.2 1.5 1.0 2.1 0.9 1.8

0.13 0.13 0.14 0.13 0.21 0.20 0.13 0.05 0.02 0.03 0.02 0.03 0.02 0.05

0.16 0.03 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02

Kulkuletti 11 [ETH 72-1, exc. unit D3], Irradiation 316 A 2 0.005 0.002 0.19 B 3 0.021 0.002 0.63 C 4 0.056 0.002 1.35 D 5 0.052 0.002 1.46 E 6.5 0.100 0.002 2.59 F 7.5 0.089 0.002 2.30 G 9 0.082 0.002 2.14 H 11.5 0.099 0.002 2.46 I 13 0.091 0.002 2.53

NV-B, J ¼ 0.00053  2.3  106 0.01 0.121 0.004 8.31 0.02 0.408 0.005 27.76 0.02 0.940 0.007 66.06 0.02 1.066 0.007 72.31 0.03 1.788 0.008 124.28 0.03 1.585 0.009 110.46 0.04 1.437 0.009 100.71 0.03 1.683 0.008 118.30 0.03 1.752 0.012 121.94

0.04 0.09 0.09 0.12 0.14 0.22 0.15 0.14 0.19

13.5 43.9 105.2 113.3 192.7 170.9 154.7 183.9 187.7

0.2 0.3 0.3 0.4 0.4 0.5 0.4 0.4 0.4

88.3 86.0 84.2 86.4 84.7 84.7 84.3 84.2 85.8

1.37 1.30 1.28 1.29 1.25 1.25 1.24 1.25 1.26

0.08 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01

Steps

Power (W)

D E F G H I J K

5 6.5 8.5 10.5 14.5 19.5 23 30

36

Ar



0.054 0.122 0.114 0.128 0.160 0.105 0.027 0.013

0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002

Kulkuletti 8 [ETH 72-9-1, exc. unit A 2 0.003 B 3 0.007 C 4 0.000 D 5 0.002 E 6.5 0.010 F 7.5 0.016 G 8.5 0.007 H 9.5 0.003 I 11.5 0.008 J 13 0.009 K 15 0.004 L 18 0.002 M 22 0.001 N 30 0.000

37

Ar



1.13 1.99 2.65 2.72 3.91 2.67 1.02 0.70

0.02 0.03 0.04 0.03 0.04 0.02 0.02 0.01

B8], Irradiation 316 0.002 0.16 0.002 0.35 0.002 0.73 0.002 1.00 0.002 2.01 0.002 1.95 0.002 1.86 0.002 1.42 0.002 1.75 0.002 2.21 0.002 1.48 0.002 1.52 0.002 0.77 0.002 0.69

38

Ar

40

Ar



%40Ar*

Age (Ma)

wo J

(continued on next page)

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

1761

Appendix A (continued) Ar



39



1.604 1.099 0.700 0.412

0.010 0.008 0.007 0.005

111.90 77.16 48.53 28.25

0.18 0.20 0.12 0.06

174.9 121.2 76.3 44.8

0.5 0.4 0.4 0.2

84.0 85.6 84.8 86.1

1.25 1.28 1.27 1.30

0.01 0.01 0.01 0.02

Kulkuletti 12 [ETH 72-1, exc. unit D3], Irradiation 316 A 2 0.005 0.002 0.13 B 3 0.020 0.002 0.68 C 4 0.045 0.002 1.20 D 5 0.051 0.002 1.37 E 6.5 0.097 0.002 2.53 F 7.5 0.085 0.002 2.24 G 8.5 0.061 0.002 1.91 H 9.5 0.061 0.002 1.68 I 11.5 0.078 0.002 2.18 J 13 0.085 0.002 2.32 K 15 0.075 0.002 1.52 L 18 0.035 0.002 1.06 M 22 0.022 0.002 0.58 N 30 0.021 0.002 0.54

NV-B, J ¼ 0.00053  2.3  106 0.01 0.084 0.003 6.18 0.02 0.395 0.005 27.46 0.02 0.805 0.007 56.88 0.02 0.964 0.008 67.34 0.04 1.779 0.009 123.30 0.03 1.573 0.008 107.65 0.02 1.261 0.007 88.03 0.04 1.137 0.008 80.65 0.03 1.491 0.009 104.43 0.02 1.620 0.011 112.96 0.03 1.072 0.008 75.14 0.01 0.761 0.007 51.91 0.01 0.416 0.006 30.13 0.02 0.391 0.005 26.90

0.04 0.08 0.10 0.10 0.16 0.21 0.16 0.18 0.19 0.19 0.16 0.12 0.07 0.07

10.4 44.3 90.4 106.2 193.7 171.1 137.9 128.4 163.0 178.5 121.9 81.9 48.3 42.8

0.2 0.3 0.3 0.4 0.4 0.5 0.4 0.4 0.4 0.4 0.4 0.4 0.2 0.3

85.2 86.5 85.4 85.8 85.3 85.5 86.9 86.0 86.0 86.0 81.9 87.5 86.8 85.3

1.37 1.33 1.30 1.29 1.28 1.30 1.30 1.31 1.28 1.30 1.27 1.32 1.33 1.30

0.11 0.03 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.03

Kulkuletti 13 [ETH 72-1, exc. unit D3], Irradiation 316 A 2 0.001 0.002 0.18 B 3 0.003 0.002 0.78 C 4 0.001 0.002 0.99 D 5 0.005 0.002 1.49 E 6.5 0.004 0.002 2.69 F 7.5 0.003 0.002 2.14 G 8.5 0.003 0.002 1.98 H 9.5 0.004 0.002 1.65 I 11.5 0.004 0.002 2.26 J 13 0.006 0.002 2.24 K 15 0.008 0.002 2.28 L 18 0.000 0.002 0.86 M 22 0.008 0.002 0.86 N 30 0.000 0.002 0.50

NV-C, J ¼ 0.000529  2.1  106 0.02 0.122 0.003 8.03 0.02 0.561 0.006 37.52 0.01 0.741 0.006 51.04 0.02 1.061 0.008 74.21 0.02 1.850 0.010 129.04 0.02 1.513 0.009 105.40 0.03 1.306 0.011 90.23 0.02 1.162 0.009 82.46 0.03 1.528 0.010 104.90 0.02 1.556 0.009 109.05 0.03 1.567 0.011 109.99 0.01 0.610 0.007 42.97 0.01 0.618 0.005 43.41 0.01 0.365 0.005 25.87

0.04 0.08 0.11 0.16 0.23 0.18 0.19 0.19 0.18 0.20 0.18 0.10 0.09 0.09

11.5 51.6 70.0 101.1 176.9 144.4 122.6 112.5 143.5 149.0 150.1 58.7 62.3 35.9

0.2 0.3 0.3 0.4 0.5 0.4 0.4 0.4 0.4 0.4 0.4 0.3 0.3 0.3

101.4 98.5 99.6 98.6 99.4 99.5 99.4 99.1 99.4 98.8 98.5 100.4 96.4 100.4

1.39 1.29 1.30 1.28 1.30 1.30 1.29 1.29 1.30 1.29 1.28 1.31 1.32 1.33

0.09 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.03

Steps

Power (W)

J K L M

15 19 23 30

36

Ar



0.095 0.059 0.039 0.021

0.002 0.002 0.002 0.002

37

Ar



2.30 1.55 1.00 0.61

0.03 0.02 0.02 0.02

38

Ar

40

Ar



%40Ar*

Age (Ma)

wo J

Worja 1, Irradiation 316 NV-C, J ¼ 0.000529  2.1  106 A 2 0.104 0.002 0.14 0.01 B 3 0.390 0.004 0.49 0.01 C 4 0.702 0.003 0.96 0.02 D 5 0.971 0.004 1.38 0.03 E 6.5 1.665 0.007 2.45 0.03 F 7.5 2.802 0.006 2.77 0.03 G 8.5 4.166 0.007 3.49 0.03 H 9.5 2.545 0.009 2.79 0.03 I 11.5 1.963 0.009 2.48 0.03 J 13 1.916 0.005 2.07 0.02 K 15 1.865 0.008 2.14 0.02 L 18 1.495 0.008 1.79 0.03 M 22 1.071 0.004 1.41 0.02 N 0.5 0.000 0.000 0.00 0.00 O 30 1.215 0.006 1.37 0.02

0.115 0.444 0.826 1.125 1.931 2.432 3.109 2.301 2.069 1.778 1.794 1.495 1.207 0.000 1.159

0.004 0.005 0.007 0.008 0.011 0.011 0.011 0.013 0.011 0.009 0.009 0.009 0.008 0.000 0.007

6.84 25.31 47.78 67.59 115.17 133.90 162.76 130.11 119.82 102.52 104.04 86.24 68.44 0.00 66.37

0.04 0.08 0.10 0.08 0.15 0.14 0.16 0.14 0.16 0.12 0.19 0.18 0.10 0.00 0.08

37.1 139.2 252.2 346.1 598.0 945.3 1359.5 859.5 690.1 660.8 646.5 519.0 389.2 0.0 426.2

0.3 0.7 0.7 0.6 1.0 1.2 1.6 1.2 1.1 1.0 1.3 1.3 0.8 0.0 0.7

16.7 17.1 17.6 17.0 17.6 12.3 9.3 12.4 15.8 14.2 14.7 14.7 18.6 261.9 15.7

0.86 0.90 0.89 0.83 0.87 0.83 0.74 0.78 0.87 0.87 0.87 0.85 1.01 94.06 0.96

0.11 0.05 0.02 0.02 0.02 0.01 0.01 0.02 0.02 0.01 0.02 0.03 0.02 284.64 0.03

Worja 2, Irradiation 316 NV-C, J ¼ 0.000529  2.1  106 A 2 0.011 0.002 0.10 0.01 B 3 0.035 0.002 0.42 0.01 C 4 0.086 0.002 0.96 0.02 D 5 0.110 0.002 1.25 0.03 E 6.5 0.270 0.003 2.98 0.03 F 7.5 0.218 0.003 2.44 0.03 G 8.5 0.269 0.003 2.97 0.04 H 9.5 0.187 0.002 2.25 0.03 I 11.5 0.165 0.002 1.67 0.03 J 13 0.135 0.002 1.80 0.03 L 18 0.285 0.003 2.78 0.02

0.073 0.305 0.731 0.900 2.116 1.722 2.018 1.616 1.195 1.245 2.018

0.004 0.005 0.006 0.007 0.010 0.008 0.009 0.008 0.009 0.006 0.009

4.89 20.83 48.74 61.50 145.74 117.75 139.71 109.51 80.87 86.52 137.52

0.04 0.06 0.10 0.13 0.16 0.17 0.14 0.22 0.20 0.20 0.21

9.6 39.0 89.8 112.4 268.1 215.7 264.8 199.1 155.1 154.7 264.4

0.2 0.2 0.3 0.4 0.5 0.5 0.5 0.6 0.5 0.5 0.6

66.3 73.5 71.7 71.1 70.3 70.1 70.0 72.2 68.6 74.2 68.2

1.24 1.31 1.26 1.24 1.23 1.22 1.26 1.25 1.25 1.27 1.25

0.15 0.03 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01

(continued on next page)

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

1762 Appendix A (continued) 36

0.117 0.123

0.002 0.002



1.35 0.63

0.02 0.02

0.993 0.473

Worja 3, Irradiation 316 NV-C, J ¼ 0.000529  2.1  106 A 2 1.163 0.007 0.21 0.01 B 3 4.349 0.013 0.80 0.02 C 4 6.699 0.017 1.25 0.02 D 5 9.578 0.019 1.78 0.02 E 6.5 15.713 0.023 2.75 0.03 F 7.5 20.694 0.036 3.04 0.03 G 8.5 17.373 0.033 2.56 0.04 H 9.5 12.495 0.026 1.76 0.02 I 11.5 15.327 0.030 2.02 0.02 J 13 9.785 0.020 1.30 0.02 K 15 9.226 0.022 1.14 0.02 L 18 9.103 0.021 1.09 0.02 M 22 7.085 0.020 0.77 0.01 N 30 10.264 0.023 1.15 0.02

40

0.006 0.005

67.98 31.69

0.13 0.08

125.6 79.0

0.4 0.3

72.4 53.9

1.27 1.28

0.01 0.02

0.365 1.346 2.131 3.002 4.877 5.896 4.958 3.503 4.261 2.703 2.531 2.445 1.862 2.721

0.004 0.008 0.012 0.014 0.018 0.017 0.017 0.012 0.014 0.010 0.013 0.013 0.010 0.013

10.45 39.26 60.65 86.33 136.38 146.46 121.08 84.66 99.78 63.05 56.69 54.24 37.94 56.88

0.03 0.06 0.06 0.11 0.18 0.18 0.15 0.11 0.13 0.07 0.07 0.07 0.06 0.08

335.8 1255.5 1964.6 2806.4 4651.2 6132.6 5116.4 3680.4 4553.8 2882.2 2749.0 2694.7 2090.7 3049.8

1.2 2.3 2.4 3.7 6.3 7.8 6.5 5.2 6.2 3.6 3.8 3.7 3.5 4.5

2.5 2.5 0.9 1.0 0.0 0.1 0.5 0.5 0.4 0.5 0.7 0.0 0.3 0.4

0.77 0.77 0.29 0.31 0.00 0.05 0.20 0.20 0.16 0.21 0.31 0.01 0.16 0.20

0.18 0.09 0.08 0.05 0.03 0.06 0.06 0.07 0.07 0.08 0.10 0.10 0.13 0.10

Worja 11, Irradiation 321 NV-A, J ¼ 0.000658  6.1  106 A 1 0.000 0.005 0.09 0.33 B 1.5 0.002 0.009 0.08 0.41 C 2 0.001 0.005 0.10 0.20 D 2.5 0.011 0.005 0.14 0.19 E 3 0.054 0.007 0.13 0.20 F 4 0.207 0.006 0.06 0.19 G 5 0.592 0.008 0.45 0.20 H 5.5 0.573 0.007 0.48 0.20 I 6.3 0.751 0.008 0.69 0.20 J 7.5 1.317 0.010 0.96 0.24 K 9.2 2.169 0.013 1.80 0.25 L 11 4.181 0.019 2.28 0.26 M 13 3.360 0.016 2.32 0.26 N 15.5 2.903 0.015 2.47 0.26 O 18 2.540 0.014 2.29 0.25

0.004 0.003 0.000 0.006 0.031 0.157 0.521 0.496 0.668 1.103 1.533 2.379 2.352 2.300 2.111

0.014 0.015 0.006 0.008 0.008 0.011 0.011 0.012 0.015 0.016 0.023 0.022 0.021 0.020

0.01 0.01 0.08 0.42 1.81 9.95 28.42 27.40 36.06 60.73 82.18 113.85 123.82 124.65 117.39

0.05 0.04 0.03 0.04 0.04 0.08 0.13 0.11 0.15 0.19 0.25 0.37 0.37 0.34 0.36

0.1 0.1 0.7 3.4 17.7 69.6 197.2 188.2 246.7 427.5 681.2 1275.5 1056.9 930.8 828.0

0.3 0.4 0.4 0.4 0.5 0.6 1.0 1.0 1.2 1.6 2.5 5.1 4.1 3.4 3.4

0.0 700.0 50.0 2.0 10.0 12.1 11.3 10.1 10.0 9.0 5.9 3.1 6.1 7.8 9.3

0.00 80.00 6.00 0.20 1.10 1.00 0.93 0.82 0.81 0.75 0.58 0.42 0.61 0.69 0.78

140.00 430.00 24.00 4.30 1.30 0.22 0.11 0.11 0.09 0.08 0.09 0.11 0.09 0.08 0.07

Worja 12, Irradiation 321 NV-A, J ¼ 0.000658  6.1  106 A 2 0.004 0.006 0.10 0.19 B 2.5 0.000 0.005 0.08 0.18 C 3 0.004 0.005 0.03 0.18 D 4 0.002 0.005 0.02 0.18 E 5 0.012 0.005 0.13 0.19 F 6 0.028 0.006 0.39 0.19 G 7 0.031 0.005 0.50 0.22 H 8 0.037 0.006 0.60 0.25 I 9.2 0.143 0.006 0.76 0.27 J 11 0.153 0.006 1.52 0.21 K 13 0.115 0.006 1.71 0.23 L 15.5 0.121 0.006 2.19 0.25 M 17 0.097 0.006 1.93 0.26 N 20 0.071 0.006 2.46 0.24 O 25 0.071 0.006 2.80 0.23 P 30 0.047 0.006 2.22 0.21

0.002 0.007 0.014 0.048 0.170 0.378 0.623 0.742 0.855 1.044 1.300 1.596 1.524 1.884 1.955 1.526

0.005 0.006 0.005 0.005 0.007 0.009 0.016 0.012 0.011 0.015 0.015 0.019 0.017 0.019 0.017 0.018

0.05 0.10 0.45 3.01 11.89 26.34 41.21 51.61 57.56 72.93 90.52 109.82 108.18 134.55 134.58 111.93

0.04 0.04 0.03 0.05 0.09 0.13 0.14 0.17 0.17 0.21 0.29 0.33 0.31 0.34 0.44 0.33

0.1 0.2 0.8 4.8 18.7 38.2 57.1 68.9 102.7 124.1 133.6 156.2 146.8 167.4 166.5 133.9

0.2 0.2 0.2 0.2 0.3 0.3 0.3 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.7

1000.0 50.0 250.0 114.0 80.9 78.5 83.8 84.3 58.8 63.7 74.6 77.1 80.5 87.5 87.3 89.7

30.00 1.00 4.90 2.17 1.51 1.35 1.38 1.33 1.24 1.29 1.31 1.30 1.30 1.29 1.28 1.27

42.00 19.00 4.20 0.63 0.16 0.07 0.05 0.04 0.04 0.03 0.02 0.02 0.02 0.02 0.02 0.02

Worja 13, Irradiation 321 NV-A, J ¼ 0.000658  6.1  106 A 2 0.004 0.006 0.17 0.20 B 2.5 0.017 0.005 0.12 0.17 C 3 0.050 0.005 0.07 0.16 D 4 0.355 0.007 0.30 0.17 E 5 0.863 0.009 0.67 0.20 F 5.5 0.835 0.008 0.48 0.24 G 6.3 1.126 0.010 0.64 0.26 H 7.5 1.465 0.011 0.95 0.26 I 9.2 4.368 0.022 1.83 0.26 J 11 5.025 0.022 2.51 0.24 K 12.5 2.749 0.015 1.81 0.25

0.004 0.014 0.038 0.256 0.631 0.616 0.847 1.084 2.133 2.658 1.697

0.005 0.005 0.005 0.008 0.011 0.012 0.012 0.015 0.022 0.024 0.022

0.07 0.59 2.08 13.78 34.01 33.79 45.57 58.54 93.01 124.21 87.77

0.04 0.04 0.04 0.08 0.13 0.12 0.15 0.19 0.35 0.36 0.31

0.4 4.2 16.0 112.1 270.7 265.9 358.4 469.5 1299.0 1524.3 843.8

0.4 0.4 0.5 0.8 1.3 1.2 1.5 1.9 5.9 5.7 3.6

410.0 18.0 7.0 6.5 5.8 7.2 7.2 7.8 0.6 2.6 3.7

28.00 1.50 0.63 0.63 0.55 0.67 0.67 0.74 0.11 0.38 0.42

32.00 3.20 0.93 0.18 0.11 0.11 0.10 0.09 0.15 0.12 0.10

Ar



%40Ar*



22 30

Ar

39

Ar

M N



38



Power (W)

Ar

37

Ar

Steps

Age (Ma)

wo J

(continued on next page)

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

1763

Appendix A (continued) Ar



39



40

0.27 0.30 0.29 0.29 0.26

2.050 1.469 1.305 1.626 1.401

0.020 0.016 0.016 0.018 0.016

105.65 74.17 67.50 83.77 72.55

0.35 0.20 0.19 0.32 0.20

1011.5 699.8 604.4 791.6 705.2

4.2 2.4 2.3 3.5 2.6

5.0 5.6 7.8 5.6 6.2

0.57 0.63 0.83 0.62 0.71

0.10 0.10 0.10 0.10 0.10

Worja 14, Irradiation 321 NV-A, J ¼ 0.000658  6.1  106 A 2 0.001 0.005 0.35 0.33 B 2.5 0.000 0.005 0.08 0.21 C 3 0.003 0.005 0.07 0.21 D 4 0.000 0.005 0.19 0.18 E 5 0.005 0.005 0.57 0.17 F 5.5 0.009 0.004 0.76 0.15 G 6.3 0.019 0.004 1.15 0.14 H 7.5 0.005 0.005 0.66 0.24 I 9.2 0.040 0.005 1.66 0.26 J 11 0.091 0.006 3.03 0.23 K 12.5 0.000 3.15 0.24 L 15.5 0.011 0.005 2.77 0.24 M 17 0.006 0.005 1.80 0.24 N 20 0.001 0.005 2.81 0.25 O 25 0.002 0.005 2.53 0.24 P 30 0.004 0.005 1.50 0.25

0.008 0.005 0.012 0.118 0.435 0.452 0.679 0.679 1.253 2.182 2.287 2.031 1.320 2.049 1.794 1.124

0.008 0.005 0.005 0.006 0.012 0.010 0.011 0.012 0.016 0.020 0.023 0.021 0.019 0.022 0.018 0.016

0.04 0.22 1.14 8.29 30.29 32.84 47.40 47.63 88.40 154.67 160.84 142.64 92.85 149.23 127.00 82.20

0.03 0.03 0.04 0.07 0.11 0.13 0.16 0.19 0.27 0.41 0.48 0.44 0.30 0.44 0.36 0.26

0.1 0.2 1.2 9.2 33.5 35.8 51.4 54.1 108.1 197.6 177.7 158.9 104.3 163.4 140.1 89.9

0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.4 0.6 0.9 0.9 0.8 0.6 0.8 0.7 0.5

1000.0 40.0 170.0 101.0 95.6 92.7 88.9 102.5 88.9 86.4 100.0 97.9 98.2 99.7 99.6 101.2

13.00 0.40 2.20 1.33 1.25 1.20 1.14 1.38 1.29 1.31 1.31 1.29 1.31 1.30 1.30 1.31

44.00 8.20 1.60 0.21 0.05 0.05 0.03 0.04 0.02 0.01 0.01 0.02 0.02 0.01 0.02 0.02

Worja 15, Irradiation 321 NV-A, J ¼ 0.000658  6.1  106 A 2 0.001 0.005 0.00 0.00 B 2.5 0.007 0.005 0.09 0.26 C 3 0.027 0.005 0.09 0.19 D 4 0.173 0.006 0.12 0.21 E 5 0.582 0.008 0.46 0.23 F 5.5 0.811 0.009 0.62 0.23 G 6.3 1.048 0.009 1.00 0.21 H 7.5 1.620 0.012 1.52 0.20 I 9.2 2.826 0.016 2.03 0.19 J 11 5.170 0.023 2.95 0.22 K 12.5 3.814 0.020 2.57 0.22 L 15.5 3.732 0.016 2.94 0.22 M 17 2.879 0.014 2.37 0.25 N 20 2.681 0.015 1.86 0.28 O 25 3.081 0.016 2.19 0.29 P 30 2.278 0.013 2.12 0.26

0.001 0.005 0.022 0.141 0.475 0.690 0.861 1.325 1.961 2.877 2.512 2.690 2.177 1.992 2.365 1.837

0.005 0.005 0.006 0.007 0.011 0.010 0.013 0.018 0.023 0.027 0.024 0.023 0.016 0.021 0.022 0.021

0.06 0.29 1.28 8.03 26.82 36.72 46.65 72.58 99.98 134.61 130.61 143.99 117.81 112.56 132.05 99.11

0.04 0.04 0.05 0.09 0.12 0.16 0.17 0.24 0.37 0.37 0.44 0.37 0.33 0.34 0.41 0.32

0.4 1.9 9.6 58.1 193.3 270.1 348.4 529.9 891.3 1590.9 1208.3 1195.7 927.1 875.4 1023.0 752.9

0.4 0.4 0.4 0.7 1.1 1.4 1.6 2.3 4.0 5.9 5.2 4.2 3.5 3.5 4.1 3.0

150.0 7.0 16.0 11.7 11.1 11.3 11.1 9.7 6.3 4.0 6.7 7.8 8.2 9.5 11.0 10.6

11.00 0.60 1.40 1.00 0.95 0.98 0.99 0.84 0.67 0.55 0.74 0.77 0.77 0.88 1.01 0.95

33.00 6.20 1.40 0.27 0.12 0.10 0.09 0.08 0.09 0.12 0.09 0.08 0.08 0.08 0.08 0.08

Worja 16, Irradiation 321 NV-A, J ¼ 0.000658  6.1  106 A 3 0.106 0.006 0.05 0.22 B 4 0.546 0.008 0.11 0.21 C 5 1.590 0.011 0.60 0.24 D 5.5 1.814 0.012 0.46 0.27 E 6.3 2.218 0.013 0.83 0.23 F 7.5 3.312 0.017 1.20 0.26 G 9.2 5.538 0.024 1.94 0.28 H 11 11.947 0.040 2.49 0.29 I 12.5 7.528 0.030 2.10 0.28 J 15.5 7.629 0.030 2.70 0.28 K 17 5.156 0.024 1.77 0.28 L 20 5.556 0.024 2.26 0.31 M 25 5.296 0.022 1.93 0.35 N 30 4.574 0.020 2.17 0.24

0.041 0.264 0.757 0.857 1.005 1.537 2.343 3.977 2.892 3.182 2.369 2.549 2.602 2.260

0.006 0.009 0.012 0.014 0.015 0.019 0.022 0.033 0.023 0.025 0.026 0.024 0.022 0.018

1.83 11.05 32.13 37.01 44.49 67.66 96.48 130.37 110.74 126.22 102.79 112.28 116.03 102.35

0.05 0.08 0.13 0.15 0.17 0.20 0.33 0.35 0.35 0.37 0.34 0.33 0.34 0.31

30.9 164.0 470.3 536.1 650.3 976.2 1645.1 3503.0 2215.1 2279.1 1542.0 1662.3 1605.9 1407.1

0.9 1.3 2.3 2.6 2.9 3.9 6.9 13.0 8.5 8.5 6.3 6.3 6.0 5.4

1.3 1.7 0.1 0.0 0.8 0.3 0.5 0.8 0.4 1.1 1.2 1.2 2.6 3.9

0.30 0.29 0.02 0.01 0.14 0.04 0.11 0.25 0.10 0.23 0.21 0.22 0.42 0.64

1.10 0.26 0.17 0.17 0.16 0.16 0.17 0.27 0.20 0.18 0.15 0.15 0.14 0.14

Kone 3, Irradiation 321 NV-B, J ¼ 0.000659  4.9  106 A 3 0.000 0.003 0.23 0.05 B 4 0.011 0.003 0.17 0.05 C 5 0.018 0.003 0.82 0.07 D 5.5 0.014 0.003 0.58 0.06 E 6.3 0.014 0.003 1.27 0.06 F 7.5 0.084 0.003 2.57 0.07 G 9.2 0.100 0.003 3.91 0.07

0.004 0.227 0.659 0.613 0.837 1.197 1.586

0.004 0.007 0.011 0.010 0.013 0.017 0.019

0.83 13.11 39.93 37.92 53.10 75.27 99.04

0.03 0.06 0.16 0.13 0.19 0.19 0.30

0.8 7.3 19.5 18.1 25.2 51.4 63.3

0.1 0.1 0.1 0.1 0.2 0.2 0.3

110.0 57.0 72.3 77.2 84.1 51.7 53.5

1.20 0.37 0.42 0.44 0.48 0.42 0.41

1.10 0.07 0.03 0.03 0.02 0.02 0.01

Steps

Power (W)

L M N O P

15.5 17 20 25 30

36

Ar



3.253 2.235 1.885 2.530 2.239

0.017 0.013 0.012 0.015 0.013

37

Ar



1.74 1.29 1.17 1.59 1.21

38

Ar

Ar



%40Ar*

Age (Ma)

wo J

(continued on next page)

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765

1764 Appendix A (continued)

Ar



39



0.08 0.09 0.09 0.08 0.08 0.07 0.06

1.879 2.648 2.885 1.450 1.226 0.815 1.007

0.020 0.024 0.022 0.016 0.017 0.013 0.014

118.61 168.85 180.87 92.03 76.78 51.52 64.13

0.35 0.44 0.44 0.31 0.24 0.16 0.20

58.3 84.1 92.9 44.2 36.3 22.7 26.1

0.3 0.4 0.4 0.2 0.2 0.1 0.2

67.0 64.0 63.2 71.0 74.5 84.7 89.0

0.39 0.38 0.39 0.41 0.42 0.44 0.43

0.01 0.01 0.01 0.01 0.01 0.02 0.02

Kone 5, Irradiation 321 NV-B, J ¼ 0.000659  4.9  106 A 3 0.000 0.002 0.16 0.05 B 4 0.003 0.002 0.65 0.06 C 5 0.006 0.002 1.16 0.06 D 5.5 0.001 0.002 1.35 0.06 E 6.3 0.002 0.002 1.84 0.06 F 7.5 0.004 0.003 3.08 0.08 G 9.2 0.003 0.003 3.62 0.08 H 11 0.000 0.003 4.64 0.09 I 12.5 0.003 0.003 4.11 0.08 J 15.5 0.003 0.003 5.32 0.11 K 17 0.001 0.003 3.63 0.09 L 20 0.002 0.003 3.49 0.09 M 25 0.001 0.003 3.54 0.07 N 30 0.001 0.003 3.19 0.08

0.028 0.187 0.655 0.625 0.893 1.440 1.674 1.983 1.881 2.429 1.690 1.518 1.575 1.417

0.005 0.007 0.009 0.011 0.014 0.016 0.019 0.018 0.018 0.025 0.019 0.018 0.016 0.016

1.55 11.85 40.62 39.50 56.69 93.21 105.60 129.28 118.31 154.72 106.86 97.55 99.61 91.32

0.03 0.06 0.11 0.11 0.18 0.30 0.37 0.37 0.41 0.44 0.37 0.36 0.37 0.36

1.3 4.3 14.0 13.7 19.4 30.8 35.1 43.1 39.4 51.3 35.2 32.4 33.0 30.2

0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.2 0.2 0.3 0.2 0.2 0.2 0.2

94.0 121.0 113.6 102.1 102.6 104.0 97.5 99.8 97.9 101.6 99.6 98.5 99.4 100.6

0.93 0.52 0.46 0.42 0.42 0.41 0.39 0.40 0.39 0.40 0.39 0.39 0.39 0.40

0.55 0.07 0.02 0.02 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01

Steps

Power (W)

H I J K L M N

11 12.5 15.5 17 20 25 30

36

Ar



0.065 0.102 0.116 0.043 0.031 0.012 0.010

0.003 0.003 0.004 0.003 0.003 0.003 0.003

37

Ar



4.17 5.63 6.04 3.00 2.58 1.39 2.24

38

Ar

40

Ar



%40Ar*

Age (Ma)

wo J

Porc Epic 1, Irradiation 321 NV-B, A 3 0.009 B 4 0.031 C 5 0.115 D 5.5 0.122 E 6.3 0.147 F 7.5 0.354 G 9.2 1.717 H 11 0.848 I 12.5 0.489 J 15.5 0.750 K 17 0.470 L 20 0.569 M 25 0.530 N 30 0.505

J ¼ 0.000659  4.9  106 0.003 0.37 0.05 0.003 0.46 0.05 0.003 1.41 0.06 0.003 1.27 0.06 0.004 1.71 0.06 0.005 2.59 0.06 0.010 5.03 0.08 0.005 3.96 0.07 0.006 3.64 0.07 0.005 4.70 0.07 0.009 4.84 0.08 0.006 4.42 0.07 0.005 4.29 0.09 0.005 3.92 0.08

0.025 0.216 0.578 0.610 0.780 1.132 2.233 1.844 1.558 2.008 2.100 1.905 1.904 1.818

0.004 0.006 0.011 0.011 0.012 0.017 0.021 0.021 0.017 0.020 0.024 0.020 0.017 0.021

1.58 12.43 37.24 37.44 46.70 68.59 123.43 106.78 97.04 117.45 126.04 114.91 115.63 108.87

0.04 0.07 0.12 0.16 0.17 0.20 0.36 0.19 0.36 0.16 0.59 0.41 0.26 0.32

3.2 15.7 46.0 46.8 58.0 122.0 505.2 268.6 166.6 244.7 164.4 194.7 185.9 175.4

0.1 0.1 0.2 0.3 0.3 0.6 2.0 1.0 0.8 1.0 0.9 0.9 0.6 0.7

13.0 41.6 26.2 23.1 25.1 14.3 0.4 6.8 13.4 9.4 15.5 13.7 15.7 14.9

0.31 0.62 0.39 0.34 0.37 0.30 0.21 0.20 0.27 0.23 0.24 0.28 0.30 0.29

0.59 0.08 0.03 0.03 0.03 0.03 0.05 0.03 0.02 0.03 0.03 0.02 0.02 0.02

Porc Epic 5, Irradiation 321 NV-B, A 3 0.021 B 4 0.156 C 5 0.362 D 5.5 0.389 E 6.3 0.501 F 7.5 0.950 G 9.2 2.193 H 11 1.358 I 12.5 1.063 J 15.5 1.436 K 17 1.172 L 20 1.039 M 25 0.974 N 30 0.775

J ¼ 0.000659  4.9  106 0.003 0.09 0.05 0.004 0.43 0.05 0.005 1.27 0.06 0.005 1.22 0.06 0.005 1.49 0.07 0.007 2.71 0.06 0.012 4.20 0.09 0.009 3.97 0.09 0.008 3.53 0.08 0.009 4.93 0.09 0.009 4.13 0.08 0.008 3.66 0.08 0.008 4.37 0.09 0.007 2.78 0.07

0.023 0.248 0.608 0.690 0.864 1.312 2.252 2.027 1.789 2.464 2.089 1.797 1.921 1.246

0.005 0.008 0.011 0.012 0.013 0.016 0.023 0.019 0.019 0.022 0.022 0.019 0.019 0.016

1.20 14.91 35.34 38.56 48.79 71.11 117.42 110.56 101.61 139.23 120.84 103.59 114.35 70.39

0.03 0.09 0.12 0.14 0.16 0.19 0.36 0.36 0.35 0.35 0.37 0.37 0.34 0.23

5.2 48.8 115.0 125.7 159.1 293.2 665.4 417.4 332.7 452.2 367.8 332.0 316.2 244.9

0.2 0.4 0.6 0.6 0.7 1.1 2.6 1.8 1.4 1.5 1.5 1.5 1.3 1.1

17.0 5.5 7.1 8.5 7.0 4.2 2.6 3.8 5.6 6.2 5.8 7.5 8.9 6.5

0.87 0.21 0.27 0.33 0.27 0.21 0.18 0.17 0.22 0.24 0.21 0.29 0.29 0.27

0.80 0.09 0.06 0.05 0.05 0.05 0.06 0.04 0.04 0.04 0.04 0.04 0.03 0.05

Argon concentrations are given in moles  1016, uncertainties are 1s. Age uncertainties do not include uncertainties of the irradiation parameter J, monitor age, and decay constants. Ages are calculated relative to the age of the monitor mineral Alder Creek sanidine (ACs-2, 1.1930.001 Ma [12]). See text for nucleogenic interference correction factors.

References [1] L.T. Aldrich, A.O. Nier, Argon-40 in potassium minerals, Physical Reviews 74 (1948) 876e877. [2] L. Bellot-Gurlet, G. Bigazzi, O. Dorighel, M. Oddone, G. Poupeau, Z. Yegingil, The fission-track analysis: an alternative technique for

provenance studies of prehistoric obsidian artifacts, Radiation Measurements 31 (1999) 639e644. [3] J.D. Clark, Y. Beyene, G. WoldeGabriel, W.K. Hart, P.R. Renne, H. Gilbert, A. Defleur, G. Suwa, S. Katoh, K.R. Ludwig, J.-R. Boisserie, B. Asfaw, T. White, Stratigraphic, chronological and behavioural context of Pleistocene Homo sapiens from Middle Awash, Ethiopia, Nature 423 (2003) 747e752.

N. Vogel et al. / Journal of Archaeological Science 33 (2006) 1749e1765 [4] J.D. Clark, K.D. Williamson, A Middle Stone Age occupation site at Porc Epic cave, Dire Dawa (east-central Ethiopia)dPart I, The African Archaeological Review 2 (1984) 37e71. [5] T. Furman, T. Rooney, J. Bryce, G. Yirgu, D. Ayalew, B. Hanan, Continental Rupture in the Main Ethiopian Rift: Constraints from Magma Source Compositions, International Conference on The East African Rift System: development, evolution, and resources, Addis Ababa, 2004. [6] R.E. Hughes, Intrasource Chemical variability of artefact-quality obsidians from the Casa Diablo area, California, Journal of Archaeological Science 21 (1994) 263e271. [7] I. McDougall, M.T. Harrison, Geochronology and Thermochronology by the 40Ar/39Ar Method, second ed. Oxford University Press, New York, Oxford, 1999. [8] C. Merrihue, G. Turner, Potassium-argon dating by activation with fast neutrons, Journal of Geophysical Research 71 (1966) 2852e2857. [9] J.W. Michels, C.A. Marean, A Middle Stone Age occupation site at Porc Epic cave, Dire Dawa (east-central Ethiopia)dPart II, The African Archaeological Review 2 (1984) 37e71. [10] A. Negash, M.S. Shackley, Geochemical provenance of obsidian artifacts from the MSA site of Porc Epic, Ethiopia, Archaeometry 48 (2006) 1e12. [11] A.O. Nier, A redetermination of the relative abundances of the isotopes of carbon, nitrogen, oxygen, argon, and potassium, Physical Review 77 (1950) 789e793. [12] S. Nomade, P.R. Renne, N. Vogel, A.L. Deino, W.D. Sharp, T.A. Becker, A.R. Jaouni, R. Mundil, Alder Creek sanidine (ACs-2): A Quarternary 40 Ar/39Ar dating standard tied to the Cobb Mountain geomagnetic event, Chemical Geology 218 (2005) 315e338.

1765

[13] D. Pleurdeau, Le Middle Stone Age de la grotte du Porc-Epic (Dire Dawa, Ethiopie): gestion des matieres premieres et comportements techniques, L’anthropologie 107 (2003) 15e48. [14] D. Pleurdeau, The lithic assemblage of the 1975-1976 excavation of the Porc-Epic Cave (Dire-Dawa, Ethiopia). Implications for the East African Middle Stone Age, Journal of African Archaeology 3 (2005) 117e126. [15] P.R. Renne, K-Ar and 40Ar/39Ar dating, in: J.S. Noller, J.M. Sowers, W.R. Lettis (Eds.), Quarternary Geochronology: Methods and Applications, American Geophysical Union, Washington DC, 2000, pp. 77e100. [16] P.R. Renne, C.C. Swisher, A.L. Deino, D.B. Karner, T.L. Owens, D.J. DePaolo, Intercalibration of standards, absolute ages and uncertainties in 40Ar/39Ar dating, Chemical Geology 145 (1998) 117e152. [17] R.B. Scorzelli, S. Petrick, A.M. Rossi, G. Poupeau, G. Bigazzi, Obsidian archaeological artefacts provenance studies in the Western Mediterranean basin: an approach by Mo¨ssbauer spectroscopy and electron paramagnetic resonance, Earth and Planetary Sciences 332 (2001) 769e776. [18] M.S. Shackley, Archaeological Obsidian Studies: Method and Theory. Kluwer Academic/Plenum Publishing, New York, 1998. [19] R.H. Steiger, E. Jaeger, Subcommission on geochronology: Convention on the use of decay constants in geo- and cosmochronology, Earth and Planetary Science Letters 36 (1977) 359e362. [20] F. Wendorf, R.L. Laury, C.C. Albritton, R. Schild, C. Vance Haynes, P.E. Damon, M. Shafiqullah, R. Scarborough, Dates for the Middle Stone Age of East Africa, Science 187 (1975) 740e742. [21] F. Wendorf, R. Schild, A Middle Stone Age sequence from the central Rift Valley, Ethiopia, Polska Akademia Nauk Instytut Historii Kultury Materialnej, Worclaw, 1974.