Sediment plutonium dating
– Sediments are complex systems containing carbon of multiple forms, sizes ranges and sources.Please contact us to discuss the nature of your research objective to ensure the most appropriate pretreatment of your sediment sample.Note: Our lab does not identify the exact type of macrofossil found in the sediment.Identification of macrofossils requires highly trained scientists, e.g.In general the plant dates are usually more reliable as they typically represent a more unique event in time.The plants were relatively short-lived as compared to the time it may have taken for the sediment to form.You are welcome to contact us to discuss the pretreatment or request that we contact you after the pretreatment to discuss options for radiocarbon dating. However, knowing the dry weight will better allow you to estimate the amount of material to send.
The lab starts the analyses immediately upon arrival of the sample so moisture will not induce contamination.Most macrofossils can be treated with (1) acid to remove carbonates, and (2) alkali to remove humic acids that might be in the sediment. Sediment and rain water or ground water can move these humic acids up or down through the sedimentary profile bringing carbon that is either younger or older into a sediment layer.In most cases, humic acids travel downward and make the underlying sediment appear to be younger (sometimes by a small amount, sometimes by a large amount of bias).For such sediment samples, when you date both the sediment and some plant material that is found in the sediment, the dates are usually very similar thus sometimes there is really no humic acid problem to worry about.
When sediments yield older ages than the plant (macrofossil), it is usually due to two possible reasons:(1) the plant remains were somehow intrusive (grew into the older sediment, perhaps due to erosion or long periods of low or no soil development), or(2) the sediment was getting some or all of its carbon during its formation from an older source (reworking or redeposition of already deposited sediment from upslope due to flooding, mass movements or other physical processes).Dating the Ca CO3 fraction of sediments is often done, but it can be problematic if the origin of the carbonate in the sediment is not well understood.