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Geochronometry • Mass Spec Services • Radioactive Tracer Applications • Sustainable Development - Nuclear Energy's Role


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Dr. Donald F. Schutz

Dr. Hewitt Jeter

Keith Noyes



Potassium- Argon | Rubidium-Strontium | Sediment Chronology | Shipping Information



  • Age Determination
  • Radiogenic Ar-40 Analysis

Sample Size:

Clean Mineral:

5 - 10 grams


2 - 5 grams

Whole Rock:

3 or 4 hand specimens or 200-300 grams

Precision, Accuracy, and Sensitivity

The determination of an isotopic age is a function of both geological and analytical factors. We try to evaluate the suitability of a given rock for age determination, but we cannot be responsible for the effect of geological factors such as argon loss, excess argon, high percentage of atmospheric argon, or sample inhomogeneity on the precision and accuracy of the calculated age. We do accept responsibility for high analytical standards including:

  • Calibration of both potassium and argon measurements with widely accepted reference materials
  • Intercalibration with recognized experts in the field

Because the absolute age of available reference materials is not known to better than 2.5% (at the one sigma level) due to sample inhomogeneity and interlaboratory differences, we assign a minimum error of 2.5% on all calculated ages even though the precision of the measurements is often better than 2.5%.

All measurements are performed in duplicate so that the precision of each measurement can be assessed for the actual sample being analyzed. If the uncertainty of the measurement exceeds 2.5%, the observed value is reported.

Our nominal limit of analytical sensitivity is 10E-08 scc radiogenic Ar-40/g and 0.01% K. Because of the variability of geological and analytical parameters, a single value for minimum detectable age cannot be cited. For a biotite with 7.5% K and 10E-08 scc radiogenic Ar-40 /g, the age would be 0.03 Ma. For a basalt with 1.0% K and 10E-08 radiogenic Ar-40 /g, the age would be 0.26 Ma. These values can serve as nominal limits of sensitivity for assessing the applicability of our present measurement technology to your problems.


  • Rb-Sr analysis.
  • 3 cogenetic rocks for Rb-Sr isochron.
  • Additional samples on same isochron
  • Sr-87/Sr-86 Isotopic ratio.

Sample Requirements:

Whole-rock isochron:

3 - 5 cogenetic rock samples

Mineral isochron:

Rock with 2 to 3 appropriate minerals

Mineral date:

Mineral with high Rb-Sr ratio


All methods assume:

  • Homogeneity of initial strontium isotope ratios
  • No re-equilibration since formation
  • Existence of closed system since formation

For the whole-rock method, the assumptions apply to the entire geologic formation or terrain. For the mineral isochron and mineral date, they apply only to the specimen analyzed.

In the whole-rock and mineral isochron methods, the value of the initial strontium isotope ratio is calculated. For the mineral date, the initial ratio is estimated.

Sr-87/Sr-86 isotopic ratios can be used to characterize rocks with regard to petrogenesis or for making distinctions between differing geologic provinces.

Mineral association and genetic relationships can be established for diverse geologic problems ranging from the study of ore deposits to determining the provenance of deep sea sediments.

Our measurements are standardized using NIST Standard Reference Materials or other internationally recognized reference materials.

Sediment Chronology

  • Pb-210 analysis
  • Cs-137 / Be-7 analysis
  • Sediment Chronology Interpretation

Sample Requirements

Sediment core 5 cm or greater in diameter, generally one meter or longer. Shipped in plastic core liner or segmented by agreement with the laboratory.


Analyses of Pb-210, Cs-137 and Be-7 in sediment cores are used to interpret sedimentation rates in rivers, lakes and estuaries. Results lead to the calculation of calendar dates at various depths in the sediment over the last 100 years, which are useful for characterizing buried artifacts or contaminants.


At least 6 transverse segments of a core, often 2 cm thick, are required to establish a data trend which can be interpreted.  Radiochemical analyses of Pb-210 and gamma spectral analyses of Cs-137 and Be-7 are standardized with NIST traceable reference materials.

Methodology and interpretation are described in:

Jeter, H. W. (2000), "Determining the Ages of Recent Sediments Using Measurements of Trace Radioactivity", Terra Et Aqua, 78, pp. 21-28


Shipping Information

Mineral Separations

If required, we will do mineral separations on age determination samples. Please be sure to supply a sample that, once separated, will provide the minimum sample size that is specified for the age determination procedure involved.



Please allow 4 to 6 weeks for delivery of results for K/Ar determinations and 6 to 8 weeks for Rb/Sr determinations

Priority Service - 2 weeks - 50% premium on total


Shipping Instructions

Samples that must pass United States Customs and should be labeled:

Scientific Samples - No Commercial Value

Please wrap and label all powdered samples carefully.


Send Samples To:

Mass Spec Services

103 South Greenbush Road

Orangeburg, NY 10962 USA

Mass Spec Services

Reading the isotopic clocks

Tel: 845-359-1151

Fax: 845-359-1102

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