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Gaps in the geologic record, called unconformities, are common where deposition stopped and erosion removed the previously deposited material.Fortunately, distinctive features such as index fossils can aid in matching, or correlating, rocks and formations from several incomplete areas to create a more complete geologic record for relative dating.Faunal Succession: Similar to the law of superposition is the law of faunal succession, which states that groups of fossil animals and plants occur throughout the geologic record in a distinct and identifiable order.Following this law, sedimentary rocks can be “dated” by their characteristic fossil content.Many sections of the Wasatch fault disturb or crosscut the Provo shoreline, showing that faulting occurred after the lake dropped below this shoreline which formed about 13,500 years ago.As this example illustrates determining the age of a geologic feature or rock requires the use of both absolute and relative dating techniques.
So I can say the second layer is younger than the first and older than the third but I have no idea whether the cake is 5 minutes or 5 million years old.
Most ancient sedimentary rocks cannot be dated radiometrically, but the laws of superposition and crosscutting relationships can be used to place absolute time limits on layers of sedimentary rocks crosscut or bounded by radiometrically dated igneous rocks.
Sediments less than about 50,000 years old that contain organic material can be dated based on the radioactive decay of the isotope Carbon 14.
Development of the geologic time scale and dating of formations and rocks relies upon two fundamentally different ways of telling time: relative and absolute.
Relative dating places events or rocks in their chronologic sequence or order of occurrence.