Adverb
radiometrically (not comparable)
By means of radiometry.
Radioactive elements are common only in rocks with a volcanic origin, and so the only fossil-bearing rocks that can be dated radiometrically are volcanic ash layers, which may provide termini for the intervening sediments. Source: Internet
There is no radiometrically datable bed at the boundary at Fortune Head, but there is one slightly above the boundary in similar beds nearby. Source: Internet
The upper boundary is defined as the appearance of Iapetognathus fluctivagus which marks the beginning of the Tremadocian and is radiometrically dated as 485.4 ± 1.9 million years ago. Source: Internet