Radiometric dating is not useful on sedimentary rocks because they are formed from the accumulation of sediments, which may contain elements with different ages. The process of sedimentation can also disturb the isotopic composition.
sedimentary
the date for which the rock formed
You can't date all minerals using the radiometric dating method because not all minerals have radioactive isotopes. In addition, the parent and daughter isotopes must remain together in a rock to use them to determine the rock's age. Because sedimentary rocks contain fragments of many rocks that could be different ages, radiometric dating is less useful for dating sedimentary rock. This technique is primarily used to date igneous rocks.
Radiometric dating of igneous rocks that relate to the sedimentary rock
Their ages
sedimentary
Radiometric dating is less useful for dating sedimentary rocks because they are made up of material that has been transported and deposited from other sources, making the age of the sedimentary rock different from the age of the material within it. Igneous rocks directly crystallize from magma and accurately retain the age of their formation through radiometric dating.
Radiometric dating is least useful for dating sedimentary rocks because they are formed from the accumulation of sediments, making it difficult to determine the original isotopic composition.
sedimentary
the date for which the rock formed
Radiometric dating can give us the absolute age of the rock. Trace fossils and the Law of Superposition can only provide the relative age of the rock. Radiometric dating is far more specific in formation analysis.
The radiometric clock is set when the rock forms, specifically when minerals within the rock crystallize. This initial crystallization is when the minerals begin to accumulate daughter isotopes and start the process of radioactive decay that can be used for dating the rock's age.
What method, and what materials, are best for dating depends on what exactly you are after.
Geologists use radiometric dating of volcanic ash layers within sedimentary rock to determine the age of the sedimentary rock. By dating the igneous rock layers above and below the sedimentary rock, geologists can establish a bracket of time within which the sedimentary rock was deposited.
You can't date all minerals using the radiometric dating method because not all minerals have radioactive isotopes. In addition, the parent and daughter isotopes must remain together in a rock to use them to determine the rock's age. Because sedimentary rocks contain fragments of many rocks that could be different ages, radiometric dating is less useful for dating sedimentary rock. This technique is primarily used to date igneous rocks.
radiometric
Age is based on fossils that are found in the rock.