They are the "initial working hypotheses" to be tested further by data.
Using these principles, it is possible to construct an interpretation of the sequence of events for any geological situation, even on other planets (e.g., a crater impact can cut into an older, pre-existing surface, or craters may overlap, revealing their relative ages).
As an example of how they are used, radiometric dates from geologically simple, fossiliferous Cretaceous rocks in western North America are compared to the geological time scale.
To get to that point, there is also a historical discussion and description of non-radiometric dating methods.
This orientation is not an assumption, because in virtually all situations, it is also possible to determine the original "way up" in the stratigraphic succession from "way up indicators".
For example, wave ripples have their pointed crests on the "up" side, and more rounded troughs on the "down" side.
Most of these principles were formally proposed by Nicolaus Steno (Niels Steensen, Danish), in 1669, although some have an even older heritage that extends as far back as the authors of the Bible.
A few principles were recognized and specified later.
This document is partly based on a prior posting composed in reply to Ted Holden.
My thanks to both him and other critics for motivating me.
Geochronologists do not claim that radiometric dating is foolproof (no scientific method is), but it does work reliably for most samples.
It is these highly consistent and reliable samples, rather than the tricky ones, that have to be falsified for "young Earth" theories to have any scientific plausibility, not to mention the need to falsify huge amounts of evidence from other techniques.
his document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale.