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AMS dating Forams

AMS Dating Forams and Ostracods

Sample size recommended (smaller AMS sizes possible – please contact us)
4-10 milligrams
Recommended container
Use vials with screw tops, microcentrifuge tubes, or counting slides before putting them inside a labeled Ziplock bag.
Please send your samples in small boxes instead of envelopes to protect the samples from being crushed during shipment.
Laboratory pretreatments are not possible for forams that are less than 10 mg.

Note – Fees are inclusive of d13C measurements, quality assurance reports, calendar calibration when applicable, and 24/7 web access to past results and pending analyses. For some tiny samples, it may not be possible to measure and report a separate d13C result. However, the total corrected fractionation will be accounted for in the final result.

Pretreatment – Carbonate samples that are less than 10 mg, such as forams, may be too small for chemical etching. They will be microscopically examined and a picture taken but not chemically etched with acid. In some cases the sample may be sonicated to remove loose debris, but in the absence of an acid etch, the result will represent the bulk carbonate content of the submitted sample. No pretreatment is necessary for tiny samples. If you have any concerns regarding the pretreatment of your sample, please contact us to discuss this further.

forams pretreatment Beta Analytic

Reservoir Correction – Please provide the appropriate Delta+R / Delta–R (localized reservoir correction) for the area of collection so that we can supply the most appropriate calendar calibration for the result. A Delta±R correction is applied to the sample that has already been corrected with the global marine reservoir correction. The value that is provided by the client is subtracted or added to this already corrected age (depending if it is a Delta+R or Delta–R value). Note: A negative Delta-R will make the date older (typically presuming freshwater dilution from the global marine average).

Sample Size for Foraminifera – Ideally we would like to receive at least 4-10 mg of clean forams so that we can measure and report d13C for the sample. We can routinely AMS date forams in the 3 mg range. However, this is working at minimum detection limit. With at least 4 mg, we can apply some treatments to remove exogenous materials. These treatments have proven to be effective in improving accuracy in some cases. Additionally, we will not be able to provide d13C and d18O values on 2 mg samples. Generally at least 3.7 mg is needed for the additional isotopic data. If we do not have enough carbonate for the d13C and d18O, we will proceed with the AMS dating and you will have the option to send additional material separately for measurements of these isotopes. In any case, the AMS dates will be corrected for total fractionation effects.

While we recommend sending at least 10 mg for ostracods, we realize that this is not always possible to obtain. At a minimum, we can accept 5 mg although there are limitations to pretreatment and d13C measurement.

You may send the ostracod samples in counting slides, but make sure that the glass cover pane is taped and cannot move during shipment. Alternatively, you can put the ostracods into a small screw top glass vial or a plastic microcentrifuge tube. The top should be secured. Place the slides, tubes, or vials into a Ziplock bag. Make sure that the bags are well padded with bubble wrap or some other material to protect them during shipment.

Found in all marine environments, foraminifera are single-celled organisms with no tissues or organs. They are small in size, ranging from several millimeters to a few tens of microns. Forams can be planktic or benthic. Planktic forams live in the upper zone of the ocean, while benthic forams are found on or beneath the ocean floor.

Forams are often used in biostratigraphic studies and palaeoenvironmental reconstructions. Benthic forams make excellent indicators of ocean depth that is why they are often utilized in palaeoceanographical research. Planktic forams are found in the open ocean and are often used as indicator of ocean currents and climates. Researchers also use forams to study marine pollution.

Ostracods (Ostracoda) are small crustaceans that are found in both freshwater and marine habitats. According to the British Geological Survey, ostracods are between 0.5 and 1.5 mm long, but a few (e.g. Gigantocypris) grow to about 25 mm. Unlike most crustaceans, ostracods are not segmented, and their heads and bodies are merged. Scientists use ostracods in multi-proxy paleolimnological investigations.