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Harm to minors, violence or threats, harassment or privacy invasion, impersonation or misrepresentation, fraud or phishing, show more. What is is about the most sedimentary rocks that makes them unsuitable for radioactive dating?
Are you sure you want to delete this answer? Sedimentary rocks contain bits and pieces of rock material that were formed during, and contain, isotopic ratios from, an earlier event. In addition, different bits of rock come from different sources, so you have a real dog's breakfast of different isotope ratios in the various fragments, none of which reflect the actual time of sedimentation.
You can actually measure the isotopic compositions, but the compositions will not have any real meaning as concerns the timing of the sedimentation. However, if you can separate out bits of autochthonous minerals that contain radioactive elements say, calcite cement it might be possible to date the time of sedimentary rock formation.
They probably contain very little Potassium.
This is used to determine the age of rocks because one isotope becomes Argon and the amount of Argon is used to date the sample. Radiocarbon dating can't be used with very old material. Unless they contain traces of something that happens to be radioactive, then there's nothing to radiometrically date.
They're formed from debris from older rocks. You can't tell the difference Related Questions Why can't we use sedimentary rocks to date the rocks dinosaurs are in?