Science topic

Radiocarbon - Science topic

Explore the latest questions and answers in Radiocarbon, and find Radiocarbon experts.
Questions related to Radiocarbon
  • asked a question related to Radiocarbon
Question
23 answers
I need to find the records for a radiocarbon analysis done in the 1970s. I have found out that the lab was Teledyne Isotopes, in Germany (lab code I). Radiocarbon's list on lab codes says that the Lab is no longer operational. I did find in the Radiocarbon journal several reports of dates from Teledyne but none are the ones I am looking for.  Any suggestions? The samples I need info on are I-9248, I-9249 and I-9250. The author who originally published the dates does not report the radiocarbon age, just a calendar date and the lab code, and he has no additional information (I spoke to him already). 
Relevant answer
Answer
I'm also looking for originals from Telfedyne Isotopes. Hoping somebody can publish the original data.
  • asked a question related to Radiocarbon
Question
2 answers
I could find younger radiocarbon age ( of the thermocline dwelling species compare to the surface-dwelling planktic foraminifera species, for a particular duration. Also, the radiocarbon age difference of the benthic species and surface species is quite low at the same time (near to 0).
Relevant answer
Answer
Dear McDonald,
Thank you for your inputs. I also think of the possibility of intrusion of water mass of higher radiocarbon concentration. I m trying to look, if Red Sea Water can affect the deep water below 2500m in the Equatorial Indian Ocean.
  • asked a question related to Radiocarbon
Question
2 answers
I've de-fatted some bone samples and analysed the "waste solution" via GC-MS to see how well the de-fatting worked before I gelatinise them. However, I don't know what the expected initial lipid content of bone is in mg/L to determine how much has been removed from the bone. The only publication I could find was by During et al. (2015), and they give the lipid content of bone in g/100g. Are there any publications that refer to the lipid content of bone in mg/L?
Relevant answer
Answer
If you obtained a morph of the original bone in the demineralisation step, then the C/N from the isotope analysis is an indication of residual lipids (little N in lipids so C/N will be higher than expected). But beware of poor preservation if the bones are old - that also pushes up C/N. Degraded bones patently do not need defatting. Also beware of incomplete demineralisation. You can also continue GC-MS analyses of successive defatting "waste solution" to determine the diminishing returns.
  • asked a question related to Radiocarbon
Question
15 answers
The radiocarbon ages (say for the Holocene) is calibrated to Before Present (1950) by using calibration curves and with software such as OXCal. If you use other dating methods such as U series or Luminescence, the age is calculated (Before Sampling Year, lets say 2018). What would be the best way to calibrate these two type of ages, simply add 68 years to 14C age? or calibrate U/Th or Lum ages to 1950?
Relevant answer
Answer
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
  • asked a question related to Radiocarbon
Question
4 answers
Hi,
I recently cores a site in the Snowy Mountains in Australia and got AMS dating done on three depths (51, 61, 67 cm). 51 cm and 61 cm came out with what I would think of as normal ages, as in 757 +-16 for 51 cm and 591+-18 for 61 cm. However, the sample at 67 cm came back as 114.7 +- 0.3%, which I found means it has a percentage of modern carbon in it(not sure how to explain it exactly). When I looked this up it was suggested that I put it into the modern carbon function of Rbacon pMC.Age to get a 'real age'. Rbacon pumped out -1102 +- 21, then they packed up and called it a night, leaving me to wonder what exactly that number means. My guess is that I should subtract it from 1950, giving me the age 848. I've talked to others who said this is completely wrong and I have no room to dispute that. Could someone give me a definitive answer on what to do with this type of data?
Thanks!
Mark
  • asked a question related to Radiocarbon
Question
2 answers
I am looking for a book
"Radiocarbon dating practices at ANU" by Gupta and Polach, published in 1985.
Can anyone please provide the link or source from where I can get this book?
Thank you
Relevant answer
Answer
Hello Praveen,
it seems that the book is available at Abebooks.com
Hope you find it!
Roberta
  • asked a question related to Radiocarbon
Question
3 answers
Do you now any alternative (and cheaper) method to radiocarbon for biological museum samples datation?
Thank you
Relevant answer
Answer
Radiocarbon is probably the most cost effective. See if others are also interested in getting dates from the samples/period - you may be able to split the costs.
Also bear in mind the precision of radiocarbon dating is not always great depending on the period. What kind of samples is it you are looking at?
  • asked a question related to Radiocarbon
Question
5 answers
.
Relevant answer
Answer
In a paper by Hebda et al. (2008) we radiocarbon date vole bones on a debris flow / sheet flood fan between much younger soil horizons.
"The bones occur between two prominent Ah horizons - the upper one
dating to 5520 ± 150 BP, and the lower one dating to 7132 ± 80 BP . The bones, however, yielded uncalibrated radiocarbon ages of 11 507 ± 52 years BP and 12 567 ± 49 years BP , 5000–6000 years older than the upper and lower bracketing soil horizons. "
The vole unit must have been remobilized from its original position and incorporated in a debris flow some 5000-6000 years later.
So the lesson here - understand the geomorphic context, and date more rather than less. In this case, only relying on the bracketing ages would have yielded results that were substantially too young.
  • asked a question related to Radiocarbon
Question
8 answers
By using floating chambers and the SrCl2 precipitation method, I collected radiocarbon isotope (C14) samples of CO2 evasion from river water surface. For the emitted CO2, the measured stable carbon isotopes ( δ13C) varied from -30.2‰ to -23.2‰, and the conventional age calculated from Δ14C values ranged from 800 to 1900 years. Could I conclude that it is the old fraction of riverine organic carbon, not the young fraction, that was degraded during fluvial delivery and emitted into the atmosphere? While numerous studies have been conducted on C14 fractionation in various biogeochemical processes, such as respiration and photosynthesis, very little has been done for the process of CO2 evasion.
Any help will be greatly appreciated. Many thanks.
Relevant answer
Answer
Hi Lishan,
I must first confess that I do not have a PhD, and so the title Dr is inappropriate for me. Moreover, since I am not an authority, anything I write should be checked with the scientific literature. However, I am attempting to write my first scientific paper on the carbon cycle and hence my interest in your question.
The high alkalinity you report suggest to me that there is a significant amount of inorganic carbon dissolved in your water. Its carbon will be millions of years old and so will have a d14C of zero. If you can measure the molarity of the calcium (and Mg) content of the water then you will have a value for the molarity of inorganic carbon, and you can subtract that when calculating your 14C age.
d18O fractionation due to evaporation (and condensation) is used to calculate paleo-temperatures, so I would expect that there is a d14C fractionation caused by evaporation too.
HTH,
Alastair.
  • asked a question related to Radiocarbon
Question
1 answer
Dear colleagues,
we've been looking for synthetic (14C-free) ethanol for some time, unfortunately it seems that commercial suppliers, at least those we have contacted, are not interested in selling small quantities (thanks again Florian Glodeanu for the tips). Does anyone know about a laboratory / department which has a spare amount (e.g., 0.5 L) of synthetic ethanol in possession and would be willing to "devote" it to our research?
Relevant answer
Sorry, I don't.
  • asked a question related to Radiocarbon
Question
2 answers
Does anyone know about a supplier which could provide ethanol free of 14C (radiocarbon), i.e. made from oil (petroleum) or any other fossil fuel?
Relevant answer
Answer
Thank you, Florian!
  • asked a question related to Radiocarbon
Question
4 answers
Question about radiocarbon :
(1) which tissues (part) should be measured, if I want to know the defoliation effect on current year NSC allocation to growth of trees.
1-year branch (if leaf is OK?), compare treated and un-treated groups; or old branches should also be measured; to compare both old-current year branch and treated and untreated?
(2) What is the difference between dry matter radiocarbon content and extracted mobile sugar-carbon-14 ? 
Relevant answer
Answer
You could measure carbon isotope values for subsamples pretreated to alpha-cellulose component of wood material and measure all three isotopes C12, C13 and C14. The variation in C13/C12 ratio is largely related to plant physiological processes (rate of CO2 assimilation rate and conductance), and can be accounted for, ie removed from the variation in the C14 measurements. You might be using C14 as a marker or trace for where sugar-C14 moves to. Regarding (2), wood material will incorporate sugar-C14 from newly fixed carbon (photosynthate or 'sugar') as well as carbon remobilised from other parts of the plant (e.g. from carbohydrate stores) fixed at other times (ie older). Using C14 as a marker will help to investigate the flows and allocation of carbon.  Other experimental treatment effects like defoliation might be adequately detectable from variation in the C13/C12 ratio and a knowledge of C3 leaf physiological theory.
  • asked a question related to Radiocarbon
Question
5 answers
Suppose there is a lake receiving DIC only from the atmosphere. Thus the radiocarbon reservoir age is zero. Also suppose we have two samples from this lake: one is terregenic leaves with a 14C specific activity of 90 PMC and a delta-13C value of -25 per mil, and the other is an in-situ gastropods with a 14C specific activity of 90 PMC too but a delta-13C value of -6 per mil (e.g., same to that of the contemporaneous atmosphere). The samples were dated in year 2016. Therefore, the conventional radiocarbon age of these samples are calculated to be 780 and 1090 yr BP. The difference is ca. 300 years, which defines the reservoir age. Clearly, this is due to the mass-dependent fractionation effect, rather than the inclusion of old carbon. The actual situation is much more complicated than this case and the lake always receives 14C-depleted DIC from other sources. My question is how to exclude this isotopic fractionation effect when studying the hard-water effect in practice?
Relevant answer
Answer
Radiocarbon data is fractionation corrected. All radiocarbon data is normalized to -25 ‰ PDB. The effects of fractionation are thus canceled out.
See:
Stuiver, M., and Polach, H. A., 1977, Discussion; reporting of C-14 data: Radiocarbon, v. 19, no. 3, p. 355-363.
  • asked a question related to Radiocarbon
Question
4 answers
I faced a problem with AMS dates of human bones. The dates of a sample of human remains appeared apparently too old, and I tend to explain this by the freshwater reservoir effect. As far as I understand, AMS dates of herbiovare animals should reflect the true age or something much closer to it, as they are not affected by the freshwater reservoir effect. But the thing is that everything I have in most of the cases is human remains. But there are several burials in the region of my interest of humans and horses buried together. So I am wondering if AMS dating alongside stable isotope (δ13C and δ15N) analysis of both individuals could help to measure the freshwater reservoir effect? Simply speaking, is it possible to detect the relationship between the level of aquatic food in human bone and deviation of its radiocarbon age (using the horse bone as a background, i.e. something with zero freshwater reservoir effect)? Could this approach be used to model true AMS dates for those human individuals with no related herbiovares, too? E.g. x=y+z, where x is the true age, y is radiocarbon age, and z is freshwater age (calculated on the basis of stable isotope levels in particular human compared to those of herbiovares in a given area).
Relevant answer
Answer
Hi Laurynas,
Ideally to determine if you have a freshwater reservoir, you need to measure radiocarbon in a terrestrial herbivore and a freshwater fish to see what the offset is in 14C years. These should be from the same context so you can be pretty certain they are from the same period (or very close in time given the possibility for reworking of midden deposits). If a freshwater reservoir is detected then you can run more measurements on samples to calculate the offset.
For your people, you will need to use the data you have just created to determine the amount of freshwater fish protein in their diet. This is where the δ15N and δ13C are necessary. Once you have a percentage freshwater protein calculated, you can apply your correction to the radiocarbon age and then calibrate normally.
If marine resources are also being exploited then the issue is further complicated as you will want to calculate the percentage input of marine protein in the diet as well. This is not applied to the radiocarbon age (uncalibrated number) but in mixing the terrestrial (IntCal13) and marine (Marine13) calibration curves when calibrating the result.
It is with all of the dietary modelling that Ricardo's FRUITS program is especially useful.
The first though though is to independently determine what the freshwater reservoir might be.
My colleagues and I from SUERC have a number of publications about marine and freshwater reservoirs, with one in review that actually applies both a freshwater and marine correction to a series of radiocarbon dates of Viking burials in Iceland.
I hope this helps as well,
Derek
  • asked a question related to Radiocarbon
Question
4 answers
I have been trying to calibrate some F14C data by 3 different ways: Oxcal, CALIbomb and clam, my samples are recent but then when I am doing the calibration it shows for a sample of 2015 as it was from 195, so I am not getting any logical calibration curve in any of the mentioned programs, does anyone know how can I fix this?
Relevant answer
Answer
You can't.  Here is the calibration curve:
It starts in 1950 so any dates after that are not defined. The 14C content of the atmosphere was badly upset by the atmospheric testing of nuclear weapons. The answer is to use dendrochronology (tree rings) if you have suitable samples.
  • asked a question related to Radiocarbon
Question
5 answers
SOM radiocarbon (Δ14C) data provide a useful metric for benchmarking predictions of SOM dynamics because it can be used to characterize the residence time in soil since fixation from the atmosphere. 14C profiles in soils show a monotonic decline with depth. What physical factors control the monotonic depletion of 14C at depths?
Relevant answer
Answer
The physical factors influencing the 14C signature of SOC with depth include aggregation and physico-chemical stabilisation, and conceivably the hydrological properties of soil (as this will affect the translocation rate of the SOC). These will be influenced by the mineralogy and texture of the soil (and in the case of aggregation, also the SOC content). Of course, the depth distribution of SOC is also influenced by external factors such as land-use/vegetation and climate and the time since initial soil formation, and these factors are therefore likely to influence the radiocarbon distribution down the soil profile.
  • asked a question related to Radiocarbon
Question
10 answers
Smaller alterations in radiocarbon dated samples are often very hard to recognise. Is it possible to use the N14 content as an indicator of samples reliability?
Relevant answer
Answer
No, this is not the major problem. Imagine that you know very precisely what was the atmospheric 14C/14N ratio in the arbitrary time.
Since metabolic chemical processes in each organism/plant/... are unique, it utilise carbon and nitrogen at various rate. I would expect that for example oak tree gathers nitrogen faster than elephant (this information is without guarantee of course). Moreover, amount of utilised nitrogen and carbon could possibly depend on local conditions, too (food, soil, etc...)
Therefore before the death of the organism ratio 14C/14N can vary. Furthermore, even after burial the sample is in contact with water, soil and so on - and ratio 14C/14N can be modified.
But no matter how carbon - saturated is food or soil, carbon 12, 13, 14 will enter all the chemical pathways in the (nearly) same rate. I used term nearly because heavier carbons aren t so mobile than lighter one, what slightly reflects to the chemical reaction kinetics. So the ratio 14C/12C or 13C/12C depends only on the natural occurence in the environment and is suitable indicator of sample isotopic fractionation
  • asked a question related to Radiocarbon
Question
5 answers
Relevant answer
Answer
Hello!
Thanks for your reply, and for the link provided, that I have not checked yet. Bayesian statistics' details are, admittedly, too deep water for me. I, for me, do grasp the basic principles and the underlying mechanics, but my background is not so extensive to let myself play around with Bayesian modeling independently from the Bayesian radiocarbon modeling facility (i.e., OxCal).
As for modeling in general, I have recently come across the problem of evaluating Logistic Regression models and I am in due course in deepening my knowledge on the topic. And I have indeed found an interesting R package for that purposes (i.e., validation and calibration).
Cheers
Gm
  • asked a question related to Radiocarbon
Question
22 answers
Is one C14 date sufficient to do age calibration and age-depth model? I am working on a peat deposit from which a 120 cm peat sample was extracted.
Relevant answer
Answer
Hi Mustapha. It all depends on the age you expect to have at the bottom of the core. I used to have up to 2000years in 1m of peat. We are even working a 3-m core which is 40kyrs...
So, 3-4 14C date range finders along the core would be nice, then you can refine it with more dates for specific intervals where you want to have a precise timing of events for the proxies you are investigating. And 210Pb is definitely a plus. Check Mires and Peat volume 7 for an overview of peat protocols and dating. Good luck.
  • asked a question related to Radiocarbon
Question
5 answers
Dead roots approx 40m long found in deep soil profile up to 100m, which formed on rock of ~3Ga age. What is the best tool to date the sample like this? I will appreciate your answers.
Relevant answer
Answer
First of all, you need to define if these roots are young organic matter (observe the characteristics), because if is true you can use a radiocarbon data (e.g. link).
  • asked a question related to Radiocarbon
Question
18 answers
Dating lab comparison.
Relevant answer
Answer
Thanks Renaud,
Your parting comment strikes a chord with me. I once had bones dated by a commercial lab that were just too good to be true so I had the same specimens redated by a research lab who found the bones were devoid of collagen! This made me suspicious of all commercial labs for a while, but the probability that the first set of results could be explained by chance were 1 in 5040! So what did the first lab date and were their ages somehow equivalent to the true age of the bones? I guess the bottom line is that researchers using dating results cannot behave like simple consumers but rather must have a good understanding of the dating and pre-treatment processes used as well as the implications they have on interpretation of dating results.