By studying sediments of various ages.docx - By studying...

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By studying sediments of various ages, we should be able to draw some inferences about the rates of continental growth. Goldstein and O'Nions (1984) found that the mean crustal residence time ( τ DM , calculated from 147 Sm/ 144 Nd and 143 Nd/ 144 Nd) of the river particulates they studied was 1.7 Ga, which they interpreted as the mean age of the crust being eroded. However, they estimated the mean crustal residence time of the entire sedimentary mass to be about 1.9 Ga. Figure 16.13 compares the stratigraphic age * of sediments with their crustal residence ages. Note that in general we expect the crustal residence age will be somewhat older than the stratigraphic age. Only when a rock is eroded into the sedimentary mass immediately after its derivation from the mantle will its stratigraphic (

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