Relative dating of fossils is based on what are pj of small change and paige hurd dating
The fossils are used to establish relative ages of the strata.
As radioactive dating can not be used to date sedimentary rocks only igneous rocks, absolute dating of fossil bearing sedimentary rocks is impossible.
The sediment of this area was laid down after ammonite A appeared 199 million years ago, and before ammonite B became extinct 195 million years ago.
This narrows the date of the delta beds to the four million years between these dates.
For example, the principle of superposition states that sedimentary layers are deposited in sequence, and, unless the entire sequence has been turned over by tectonic processes or disrupted by faulting, the layers at the bottom are older than those at the top.