Amgueddfa Cymru - National Museum Wales

Fields and scope notes

Each record in the database summarises the information that can be gleaned about a radiocarbon date from the published. A wide range of information was gathered, including details of the sample itself, its site context, and the numeric results of the analysis.

To be allocated a record in the database, a publication had to include either a laboratory code and / or an uncalibrated date and uncertainty. Instances where dates are only published in calibrated form, without a laboratory code were not included.

Each of the database fields is listed below with notes to summarise the types of information it incorporates.

Lab

The laboratory code issued for a radiocarbon analysis. Laboratory codes are unique values in the form [Laboratory ID] - [analysis number]. In some instances where laboratory numbers are not listed, or where more than one determination has been assigned the same laboratory code, the project staff have added a unique identifier within square brackets (eg, GrN-1234[a]). Where there is uncertainty about a laboratory code as used by a specific publication, this is documented in the Notes fields.

Date

The radiocarbon age returned by the laboratory. Where there is uncertainty about the age noted in a specific publication, this is documented in the Notes field.

Uncertainty

The level of uncertainty accompanying the radiocarbon date. Where there is dispute about the level of uncertainty used in a specific publication, this is documented in the Notes field. It should be noted that Ashmore et al (2000, 46) recommend that the uncertainties associated with determinations issued prior to the mid-1980s should be regarded as a minimum figure. This should be borne in mind when using the 'raw' data presented here.

Start1 and End1

1 sigma calibrated dates obtained by running the determination through Oxcal v4 using the IntCal 04 curve.

Start2 and End2

2 sigma calibrated dates obtained by running the determination through Oxcal v4 using the IntCal 04 curve.

13C

The level of 13C in a sample, useful for assessing the degree of fractionation which might affect the radiocarbon date.

Name

The name of the site from which the sample was derived. It should be noted that different authors frequently record the same site by different names. For ease of searching site names have been standardised in this database, but it should be noted that the national grid reference (NGR) field is often a more accurate indicator of a site's location.

NGR

The Ordnance Survey national grid reference which indicates a site's location. All published site grid references have been verified by comparing the entry with Ordnance Survey maps.

East1 and Nrth1

Ordnance Survey numeric grid references. These are provided to allow the incorporation of this dataset within a Geographical Information System.

Description: descrip

A very basic description of the site from which the sample was derived. These are rarely more than minimal notes to give an indication of the broader context from which the sample was derived and the reason it was obtained.

Material

The material from which the radiocarbon date was derived. The sampled material is listed according to a hierarchy of information. First, the sample types generally recognised by laboratories in their sample submission literature; second, by species; and third, by the part of plant / animal where applicable (eg Bone (human, femur) or Charcoal (alder, twigs)).

Categories of sample material currently include: bone, charcoal, cremated bone, organic sediment, peat, plant material, seed, shell, wood. Other categories are used where the information in the published source cannot be convincingly allocated to the above (eg, hair, skin).

Context: context1 to context5

A description of the specific context / core depth from which the sample is derived. Different publications record contexts in different ways, as a result there are five versions of this field in the database. The information in these fields could be used, in conjunction with the original publication, to assess the 'value' of a determination as listed in the importance fields.

Importance: imp1 to imp3

An assessment of the interpretative value of a radiocarbon determination. This might include information on the pollen spectra recorded at the sample point, the archaeological phase it relates to, or finds which are present in that context. Different publications record "importance" in different ways, as a result there are three versions of this field in the database. The information they contain should not, however, be considered to be either accurate or definitive without subsequent reading of the original publication.

Caution: caut1 to caut2

Authors frequently have reservations about the results of radiocarbon dates. This field summarises those reservations and includes comments on original sample size, explanations of potential anomalies in the results obtained, and observations about the implications of the dates. Different publications record different kinds of cautionary notes, as a result there are two versions of this field in the database.

Notes: notes1 to notes10

Additional information including, the location of any museum specimens sampled, any anomalies noted in the published information, or alternative versions of the lab codes, dates, or uncertainties which have been published. Since different publications provide different types of information, there are ten versions of this field.

References: ref1 to ref19

The published sources which note the determination. The nineteen versions of this field contain full biblographic references.

Bibliography

Ashmore, P., Cook, G. T. and Harkness, D. D. (2000) 'A radiocarbon database for Scottish archaeological samples'. Radiocarbon 42:1, 41-8.