Dating Options

Waikato offers a range of dating options for our submitters depending upon the level of precision required and the sample size.

Standard Radiometric Dating: Samples large enough to be dated by the direct counting, Liquid Scintillation method (see Table 1).
Express Option: An express service option is offered for urgent samples. Standard precision radiometric dates may be express dated in 10 working days (bone - 20 working days). This option does not apply to AMS dates and is not recommended for older samples (>30, 000 years).

AMS Dating: Samples that are too small to be dated by the Standard Radiometric method can be dated by the AMS (Accelerator Mass Spectrometry) technique. Chemical pretreatments, CO₂ production and graphitization are undertaken at Waikato. Graphite is analysed at the Keck AMS Radiocarbon Laboratory, University of California, Irvine and the National Isotope Centre, GNS Science, Lower Hutt.

Sample Type and Size Requirements

A wide range of sample types can be submitted for dating. We can advise on the suitability of different materials and the most effective pretreatments. Table 1 shows the ideal weights necessary to achieve the level of precision (standard error) listed in Table 2.

Table 1: Sample size requirements (Dry weights*).

Material	Radiometric dating (ideal weight)	Radiometric dating⁺ (minimum weight)	AMS dating (minimum weight)
Wood	10-20 g	2.0 g	100 mg
Charcoal	8-12 g	1.0 g	100 mg
Carbonates	35 g	5.0 g	60 mg
Peat^	10-100 g	5-10 g	1 g
Bone^	100-200 g	50 g	1-5 g
Lake Sediment^	30-100 g	10-20 g	1 g

* Recommended weights given are for clean, dry material.
^ Ranges reflect varying carbon content (weights approximate).
⁺ Sample standard errors will increase as radiometric samples size decreases (see Table 2).

Table 2: Approximate size of standard error (±1 sigma) for radiocarbon samples.

Magnitude of standard error for standard radiometric samples
Sample age (yrs)	Precision for full-sized (~ideal weight) sample	Precision for 50% ideal weight sample	Precision for 20% ideal weight sample	Magnitude of standard error for AMS samples
500	40	60	100	40
1000	40	60	100	40
5000	50	65	110	50
10,000	75	100	170	70
20,000	170	200	350	200
30,000	350	570	850	700
40,000	900	2500	5000	1500
50,000	2700	-	-	-

Sending Samples

Samples should have non-contemporaneous materials such as rootlets and shells removed by tweezers before drying and packaging. Samples should be dried at in a dust-free environment, and packed into clearly labelled heavy grade polythene bags. Please do not place paper labels in sample bags.

All packages should be labelled: 'Scientific samples only - no commercial value' and accompanied by sample submission forms. Please write our current MAF permit number (given below) on the outside of the package.

IMPORTANT

Any samples incorrectly labeled, or samples that are not accompanied by sufficient documentation may be held on entry into New Zealand, with subsequent delays before they are released. Please assist us by following these guidelines:

Our laboratory has a permit from the Ministry of Agriculture and Forestry (MAF) that permits the importation of samples for radiocarbon dating from overseas. It is important to include a copy of the permit in with the package [MAF Permit] when material is sent to us from outside New Zealand.

Our current MAF permit number is: 2011 042746

Materials such as ivory, clam shells or coral are covered by the CITES agreement (Convention on International Trade in Endangered Species). Under this agreement there is strict control governing the importation of these materials (for more information visit the CITES web page). Because of the difficulty of distinguishing live from fossil corals, all coral samples (and other samples listed under the CITES agreement) must be correctly declared when entering customs and accompanied with documentation stating expected age and sampling location.

If you wish to send us coral collected live please contact us and we will supply you with the appropriate CITES exemption code which must be written on the outside of the package. Please note: you are responsible for arranging the necessary permit to export the sample from the country of origin.
PLEASE NOTE: WE ARE UNABLE TO RETURN SPARE MATERIAL

We recommend that samples are sent by courier or registered post. Please contact us before sending so we can track the progress of your samples. Address the package to:

Attn: Dr. Alan Hogg or Dr. Fiona Petchey
Radiocarbon Dating Laboratory
University of Waikato
Gate 9
Hillcrest Road
Hamilton, 3240,
New Zealand

It is our policy to notify all customers (by email) upon the receipt of their samples.

Turnaround Time

The turnaround time fluctuates with demand, but radiometric dating averages 6 to 8 weeks and AMS around 10 weeks (expect longer turnaround with bone samples regardless of technique). Our Express Dating service (radiometric only) guarantees a date in 10 working days (excludes bone), but it is wise to contact the laboratory first. The turnaround time may be longer for large batches of samples.

Please note: We are closed over the Christmas, New Year and Easter periods.

Sample Type

A variety of pretreatment procedures are employed at the Waikato Dating Laboratory to ensure as much contamination as possible is removed. Here is a list of commonly dated sample types and potential problems.

Pretreatment: All samples are closely inspected to isolate the most reliable fraction for dating. Often a sample may not be homogeneous, or there may be extraneous materials such as rootlets, thread, glue or some other visible contaminant in the sample. The sample is then washed in distilled water and crushed, or milled, to increase the surface area for subsequent pretreatment.
Charcoal and Wood are pretreated using a dilute acid / dilute alkali / dilute acid treatment (commonly termed ABA). For this method the sample is heated in HCl, rinsed, heated in NaOH, rinsed and then treated again in hot HCl, rinsed and dried. The chemical concentrations, temperature and length of pretreatment vary depending on the sample.
Please note: it may be necessary for the charcoal and wood to be identified to short lived species to avoid problems of inbuilt age. More information on inbuilt age can be found here.
For old wood samples (>20,000 BP), we recommend the cellulose fraction be extracted. The sample is treated with sodium chlorite to isolate holocellulose, rinsed, then treated with sodium hydroxide, and rinsed again (solvent extraction may be required depending on sample preservation). The sample is then washed with HCl, rinsed and dried. We will perform cellulose extraction and solvent extraction upon request at additional cost.
Bone is tested for suitablity prior to dating, acid washed in dilute HCl to isolate the bone protein, filtered, then gelatinized to remove contaminants. Gelatin designated for AMS dating is then ultrafiltered to further purify the gelatin. The gelatin is filtered then freeze dried.¹⁵N and ¹³C values are included in the cost of bone pretreatment. We recommend contacting the lab before dating bone for the first time.

Soil and Peat: Commonly, the humin fraction is isolated from peat, soil and lake sediments using the ABA method. However, if requested we can isolate and date the total organic fraction or the humic fraction of the sample. The total organic fraction is isolated with a HCl wash which removes inorganic carbon and absorbed CO₂, rinsed and dried. Humic acid is isolated by collecting the NaOH fitrate which is acidified with HCl to precipitate the humic fraction, then rinsed and dried.
Marine Shell samples are routinely etched with dilute HCl to minimise the possibility of contamination through isotopic exchange between the sample and its environment. All aragonitic shell samples are routinely tested for recrystallisation prior to dating. More information on marine shell dating and problems can be found here.
Freshwater/Terrestrial Shells undergo similar pretreatment to marine shell samples. Freshwater and terrestrial shells may obtain their carbon from a source (or reservoir) that is not well documented and may give results that are difficult to interpret. More information on reservoir effects can be found here.

If you require detailed information about a specific pretreatment method or have questions about a particular sample type, please contact us.

(See our price list for optional pretreatment charges).

Interpretation of Calibration Results and Age Reports

We routinely present the client with an Age Report sheet as well as calibrated ages, which are emailed as Acrobat Reader pdf documents. Click on the following link if you are unsure how to interpret the age reports. Explanation of the calibrated OxCal plots can be found at the Oxford Radiocarbon Accelerator Unit's calibration web pages. Further information on OxCal can be found here.

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