Six laws of relative dating
It gave Steno a reliable, geometrical means of distinguishing minerals from each other as well as from rock clasts, fossils and other "solids embedded in solids." Steno did not call out his Law and his Principles as such.His own ideas of what was important were quite different, but I think they are still well worth considering.The thick, dark, gray layer at the bottom is made of basalt. You have just used the principle of superposition to interpret the relative ages of the layers.This principle states that in a sequence of undisturbed sedimentary layers or lava flows, the oldest layers are at the bottom.In 1669, Niels Stensen (1638-1686), better known then and now by his Latinized name Nicolaus Steno, formulated a few basic rules that helped him make sense of the rocks of Tuscany and the various objects contained within them.His short preliminary work, (Provisional report on solid bodies naturally embedded in other solids), included several propositions that have since become fundamental to geologists studying all kinds of rocks.
However the relative ages of rocks is more commonly determined by the presumed ages of the fossils found in the sedimentary layers.Using relative dating principles and the position of layers within rock, it is possible to reconstruct the sequence of geologic events that have occurred at a site.