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Article Radiocarbon and luminescence dating of overbank deposits in ...

Abdelkader Dehbi thanks but I could not see a direct answer in the paper. Yes it is necessary to calibrate 14C dates to relate to calendar where luminescence ages give direct calendar years. For ages over 20 ka ~50 years are insignificant compared to minimum %10 error of luminescence. But what if we are dealing with more recent ages and trying to calculate rates of earth processes?

Because radiocarbon years are not the same as calendar years, the calibration software gives the option to do a conversion for you, and so you can express radiocarbon ages in calendar years. You can do the same for the luminescence ages by referencing against the year of analysis. For young samples this is sensible, but when the landscape processes are much older then the reference point becomes less relevant, but you must still remember to calibrate radiocarbon dates and express them in calendar years BP for comparison with luminescence dates.

Stephan Woodborne thanks for your anwer. My study concerns a fluvial terrace dated to 2ka BP with multiple dates/methods from same level. They are in good correlation and 50-70 years BP calibration issue are within the error range.

Dear M. Korhan Erturac ,

I think, you should convert all ages to BP convention. Otherwise, how can you describe the different time points from different dating methods to the author? Moreover, your readers are familiar with the BP or b2k convention. All other transformations would be confusing, I suppose.

Thanks, this is the main idea, today we are within the error range so 70 years dont matter, but in the near future we will date more recent events, with smaller error range. Like after 2020 pandemy efes bey enjoyed the coast for the very first time in late may, early june. We will forget BP after the definition of anthropocene

Turhan Dogan thanks for the answer. This helps in many ways. The question is as the reliability of lumi ages increase everyday we will use them more to achieve more recent dates aiding the 14C chronology. The interpretation of the dates will possibly vary for the question. For example if we take samples from a geological layer constraining an historical earthquake with a known date of say AD 1850 we can easily calibrate OSL dates to calender years (AD). How about any geological event without historical dates?. This discussion was really helpfull. Thanks all

The radiocarbon community has been working on inter-lab comparisons, laboratory systematic errors, and the difference between the measurement precision vs. the event precision. Look at van der Plicht et al. 2020 (DOI:10.1017/RDC.2020.22) for the details on these controls. The outcome is a realistic self assessment of errors at community level. To the best of my knowledge this has not been done in the luminescence community. The result is that any errors in dose rate and equivalent dose measurements are limited to the precision (not accuracy) of the OSL lab in question. Analytical error alone is not sufficient to give a reasonable estimate of age accuracy. While radiocarbon has issues with the multimodal calibration , it has the capability of presenting realistic errors. This needs to be taken in to account when assigning OSL ages in the problematic ranges for radiocarbon calibration when OSL seems like the preferred method. The assumption is that the OSL method is absolute, but this should imply that any lab would get the same result on the same sample.This has not been demonstrated. Even if between-lab analyses were to match, there are other OSL errors that affect the absolute interpretation of the results. Issues of dose inheritance that affects younger OSL samples, for example, or moisture estimates through time. If it is possible, there is merit in applying both radiocarbon and OSL together. I did this on the Middle Stone Age site, Rose Cottage Cave, here in South Africa.

Dear Dr. Woodborne, I completely agree with your detailed respond such as the statement "Analytical error alone is not sufficient to give a reasonable estimate of age accuracy". As a matter of fact OSL dating relies on many variables which are subject to both analytical and human error. At this stage, as a Quaternary geologist trying the find the date and rate of events for the late Pleistocene, I am satisfied with the correlation of the two dating methods. I have a nice chance follow suggestion within a very young fluvial section (~700 yr) where 14C and dendrochronology methods fit each other perfectly, so I can try OSL (and pIR-IRSL) as well.

Oxcal callibration is the reply to your answer Dr. Erturac. Without adding more years. The only possible problem lies behind the fact that the OXcal callibration curve in some parts is almost flat. What does this mean? Simply that for one event, more than one possible ages can be revealed (with associated probabilities). In that case, archaeo-geological context is really important.

Dear M. Korhan Erturac,

I have a question for you: Why are you going to use ages obtained from different dating methods? If radiocarbon dates are accurate and reliable, then why you go for other kinds of dates? In some cases, for example, when 14C dates are obtained from highly calcareous bulk sediment which may deliver significantly older ages than reality, it is recommended to use other kinds of datings to validate the accuracy of the 14C ages (e.g., Djamali et al., 2016: DOI 10.1007/s00334-015-0545-8). Besides this, using Lumi ages may be of help for sediments older than the 14C age range.

As explained correctly by others, you should convert 14C ages to calendar ages using one of the several available calibration software to make them comparable with dates obtained by other dating techniques.

Best, Reza

Dear Reza Safaierad, George S. Polymeris and all

Thanks for the discussion and your valuble contributions. For my part I decided to choose to calibrate the radiocarbon ages to calendar dates (CE/AD) if I am working for the last 2k and calibrate the OSL ages accordingly. If I am working at a time range further back through the Holocene, best to use BP where the +70 years would be within the error range for both methods and best for correlation with the regional climatic and geological events. What I understand from the responses that a through research focusing on the correlation of different Quaternary dating methods (210Pb, OSL, 14C, CN, ESR, dentrochronology, U-series etc.) is needed for different time periods. Dating methods and approaches are the topic of physics and chemistry but on the other hand geological time and events are geologist's main problem regarding major events such as eruptions and earthquakes.

Dear Korhan

As you know my new lab includes also 14C dating. I will be glad to help you measure, organise sampling or even callibrate C14 ages, especially versus luminescence ages.

All my best