Fossils dating rock
The basis for assuming that like fossils indicate contemporary formation is faunal succession.However, as previously noted, times of volcanism and metamorphism, which are both critical parts of global processes, cannot be correlated by fossil content.Sedimentary rocks (made from mud, sand, gravel or fossil shells) and volcanic lava flows are laid down in layers or beds.They build up over time so that that the layers at the bottom of the pile are older than the ones at the top.In science there are many key concepts and terms that are crucial for students to know and understand.Often it can be hard to determine what the most important science concepts and terms are, and even once you’ve identified them you still need to understand what they mean.The textbooks speak of the radiometric dating techniques, and the dates themselves, as factual information.Far from being data, these dates are actually interpretations of the data.
It is based on the fossils found in rocks of different ages and on radiometric dating of the rocks.
Not every rock can be dated this way, but volcanic ash deposits are among those that can be dated.
The position of the fossils above or below a dated ash layer allows us to work out their ages.
Correlating two separated outcrops means establishing that they share certain characteristics indicative of contemporary formation.
The most useful indication of time equivalence is similar fossil content, provided of course that such remains are present.
Geologists call this simple observation the Principle of Superposition, and it is most important way of working out the order of rocks in time.