Sedimentary rock is made of particles derived from other rocks, so measuring isotopes would date the original rock material, not the sediments they have ended up in.
However, there are radiometric dating methods that can be used on sedimentary rock, including luminescence dating.
Others measure the subatomic particles that are emitted as an isotope decays.
Some measure the decay of isotopes more indirectly.
Geologists often need to know the age of material that they find.
They use absolute dating methods, sometimes called numerical dating, to give rocks an actual date, or date range, in number of years.
This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.
These use radioactive minerals in rocks as geological clocks.It will probably fail, but what would a reasonable person conclude from that? All they indicate is that the methods are not infallible.Those of us who have developed and used dating techniques to solve scientific problems are well aware that the systems are not perfect; we ourselves have provided numerous examples of instances in which the techniques fail.All radiometric dating methods measure isotopes in some way.Most directly measure the amount of isotopes in rocks, using a mass spectrometer.Because of the fairly fast decay rate of carbon-14, it can only be used on material up to about 60,000 years old.