Methods
We offer a range of dating methods applicable to archaeology, geohazard and geotechnical projects as well as "deep time" geological studies.
Most of our work has until recently involved biostratigraphy and (for archaeological and geohazard studies) radiocarbon dating and oxygen isotope analysis.
In partnership with other laboratory facilities we are now able to offer U/Th, Amino Acid Racemization, OSL, 210Pb, 137Cs and 87Sr/86Sr dating. We would be pleased to discuss the suitability of any of these methods for your project.Biostratigraphy
Biostratigraphy is the branch of stratigraphy which assigns relative ages to sediments using the fossils contained within them. Information from fossils can also be used to infer environments of deposition. Mainly because of the small size of samples available, industrial biostratigraphy is usually concerned with very small fossils which for practical convenience are typically placed in separate disciplines each of which requiring its own expert preparation and analysis. The three most commonly used fossil types are calcareous microfossils, calcareous nannofossils and palynomorphs.
Radiocarbon (14C) dating
Suitable for dating sediments up to c.45Ka old as long as they contain suitable biogenic material (molluscs, microfossils, plant material). Non-marine as well as marine and terrestrial sediments can be dated using this method. Each sample is prepared in the same way as for a micropalaeontological analysis. Suitable specimens are selected by picking through the residue.
Oxygen isotope (δ18O) analysis
Oceanic sediments containing planktonic foraminifera can provide a curve which can be compared with a local or global standard. Useful for recognising MIS (oxygen stages) but requires calibration to improve certainly. Requires multiple closely spaced samples to be of any use. Each sample is prepared in the same way as for a micropalaeontological analysis. Suitable specimens are selected by picking through the residue. Only a few specimens (c.10) are required.
Uranium-Thorium (U/Th) dating
This method can be used on carbonate samples up to about 500ka old. They must be from a closed system (e.g. corals, travertine and stalagmites). Samples from open systems (e.g. foraminifera and molluscs) will likely give erroneous ages. There are several other issues to consider before submitting samples for dating (e.g. samples with a relatively low initial U/Ca and uranium concentration tend to uptake uranium after deposition and through diagenetic processes and produce aberrant ages). 30 - 50mg of coral is sufficient but this must be free of clay particles, etc. An initial mineralogical examination maybe required so as to preferentially select aragonitic material.
Amino Acid Racemization (AAR) dating
AAR dating relies on time dependent breakdown of proteins and their constituent amino acids in fossils such as foraminifera, ostracods and molluscs. Claims that dates between 10 years to 2.5Ma are achievable have been made.
Caesium (137Cs) dating
Most suitable for dating very recent sediments suspected of being less than 70 years old. Requires multiple samples from undisturbed core.
Lead (210Pb) dating
Most suitable for dating very recent sediments suspected of being less than 100 years old. Requires multiple samples from undisturbed cored sediment.
Strontium (87Sr/86Sr) dating
Most suitable for dating marine marine fossils suspected of being >500ka old.
Optically Stimulated Luminescence (OSL)
Useful for dating sediments 0 - 500ka old