Sedimentary rock age dating
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There are situations where it potentially fails -- for example, in cave deposits.
For example, wave ripples have their pointed crests on the "up" side, and more rounded troughs on the "down" side.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.An early summary of them is found in Charles Lyell's .In no way are they meant to imply there are no exceptions.They are applied by geologists in the same sense that a "null hypothesis" is in statistics -- not necessarily correct, just testable.
In the last 200 or more years of their application, they are valid, but geologists do not assume they are.The simplest situation for a geologist is a "layer cake" succession of sedimentary or extrusive igneous rock units arranged in nearly horizontal layers.In such a situation, the "principle of superposition" is easily applied, and the strata towards the bottom are older, those towards the top are younger.The layers of rock are known as "strata", and the study of their succession is known as "stratigraphy".Fundamental to stratigraphy are a set of simple principles, based on elementary geometry, empirical observation of the way these rocks are deposited today, and gravity.For example, the principle of superposition is based, fundamentally, on gravity.