I know there are several techniques for dating sediments but which method would be appropriate for determining the age of sediments of marine environments deposited in 20-30cm below the uppermost bottom layer ?
If in coastal areas with high sedimentation rates, for clayey sediments 210Pb can be useful in estimating sedimentation rates. Additionally, 137Cs can be a marker of events. In some cases, plutonium isotopes can be used. Read the literature to know the utility and limitations of each of these technique (e.g., Handbook of Environmental Isotope Geochemistry Edited by Baskaran, M.)
If you have any lime shell material, 14C can be a good dating tool. Tiny microfossils such as foraminifera can be picked from different depths in a sediment core and dated to construct a chronological record
There are three general approaches that allow scientists to date geological materials and answer the question: "How old is this fossil?"
1- First, the relative age of a fossil can be determined. Relative dating puts geologic events in chronological order without requiring that a specific numerical age be assigned to each event.
2- Second, it is possible to determine the numerical age for fossils or earth materials. Numerical ages estimate the date of a geological event and can sometimes reveal quite precisely when a fossil species existed in time.
3- Third, magnetism in rocks can be used to estimate the age of a fossil site. This method uses the orientation of the Earth's magnetic field, which has changed through time, to determine ages for fossils and rocks.
Are we talking about unlithified marine sediments with sedimentation rates that could be expected for the continental slope? Radiocarbon dating on carbonates could work. For that, I would pick planktonic foraminifers of one species. For AMS dating you probably need around 0.020 g to be on the safe side.
Your best bet would seem to be Pb210 unless the sedimentation rate is extremely low in which case you might be able to use C14 on planktic Foraminifera tests.
It depends on the materials you have in the sediments. Radiocarbon dating on carbonates or C14 on plankton would be suitable.
Dear Mr. Samad: You have to investigate in more detail your sediments and clearly distinguish between cement minerals, which are autochthonous and amenable to radiometric dating given they contain K, U, Th, and Rb such as some micaceous phyllosilicates, cryptomelane or uranyl-bearing supergene minerals. The majority of mineral phases might be of detrital origin which have only some implications on the lithological processes in the provenance area and give you a maximum age of formation which has very little meaning for your problem. Lithostratigraphic correlation with other strata of a defined age of sedimentation is possible but needs a lot of experience because you have to take into consideration lateral facies changes between the two. I wish you much success
In case of very young sediments I refer to the table given by Prof. Minas
H.G.Dill
It depends on the sample source. If you collect sediment from the near shore of Bangladesh coast, Radiocarbon dating would be suitable, I think.
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