Towards an Absolute Chronology for the Iron Age of Inner Asia
Hall, Mark E., Antiquity
For half a century now - ever since radiocarbon dating began - there have been regional reconciliations between relative chronologies and the new absolute dating. Sometimes they have been friendly, some times less so when the two schemes have not matched well. For Inner Asia - centre of the Old World - there is belatedly now the means to resolve some fundamentals.
This note reviews and calibrates some radiocarbon determinations for the Iron Age cultures of Inner Asia using a Bayesian calibration program. FIGURE i is a map of the sites covered in this paper. Inner Asia is generally defined as the area of the Eurasian continent where nomadism and pastoralism are the main forms of subsistence (Sinor 1990a). The Bayesian methodology allows the incorporation of dendrochronological data, historical information and stratigraphic relationships that can refine the calibration of radiocarbon determinations (Biasi & Weldon 1994; Buck et al. 1995; Litton & Buck 1995: 12-18). This framework makes possible a preliminary absolute chronology for the Iron Age of Inner Asia.
When many of the Inner Asian Iron Age dates were originally published, the 14C calibration curve had not been determined, nor was the statistical nature of radiocarbon dates fully appreciated. As many of the dates were rejected and/or ignored (Jettmar 1970: 255,267-9), the chronology for the cultures of Inner Asia is still largely based on cross-dating with Achaemenid, Assyrian, Chinese, Greek and Roman artefacts and art styles (Bunker 1992; Farkas 1970; Hiebert 1992: 120-22; Jettmar 1967; 1970; 1981: 14955; Karo 1991; Martynov 1991; Watson 1972). This methodology may be satisfactory for the Sarmatians and Scythians residing near the Black Sea; it is problematic for cultures such as the Altai Scythians and Tagar culture that contain few dateable imports. For these cultures and others, the chronologies are based on similarities of their art, horse gear and weapons to those of the Black Sea Scythians and Sarmatians (Bunker 1970a; 1970b; Chatwin 1970; Gryaznov 1969; Martynov 1991). Chronologies based on the similarities between artefact styles are plagued by uncertainties on where the styles originated, how fast they spread and how long they stayed in use (Deetz & Dethlefsen 1965).
Assumptions concerning the [.sup.14C] determinations
The radiocarbon dates used in this study were compiled from a variety of publications in Chinese, English and Russian. Since these dates were produced over the last 30 years under different conditions and by different laboratories, the following assumptions and corrections are made:
1 The radiocarbon determinations listed are based on a [.sup.14C] half-life of 5568 years. Dates based on a half-life of 5730 years are converted to the 5568 half-life by dividing by 1.03 (Mook et al. 1987: 104).
2 Even though the exact pretreatments between the laboratories differ, it is assumed that they were sufficient to remove humic acids and contaminants. A review of the effectiveness of different pretreatments for humic acid removal can be found in Zaitseva (1995). It is also assumed that correction for isotopic fractionation (.[sup.13C]) was done by the laboratory and is reflected in the date. The validity of this assumption can be questioned, but it needs to be noted that the Vernadsky Institute Laboratory in Moscow was doing this as early as 1966 (Vinogradov et al. 1966: 292-3).
3 Averaging, or 'pooling', of radiocarbon determinations is done only on [.sup.14C] determinations from the same context and from similar materials (Bowman 1990: 58, 59; Ward & Wilson 1978: 21). For the cases listed in this study, all the pooled samples consist of wood that was used to manufacture a coffin or burial chamber. The wood used in the construction of a burial structure is assumed to have been harvested at no significant difference in time before the burial.
Mathematics and calibration
With these assumptions in mind, the suites of Inner Asian Iron Age radiocarbon determinations were calibrated using OxCal, version 2. …