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Relative dating cross cutting

Relative time places events or formations in order based on their position within the rock record relative to one another using six principles of relative dating.Relative time can not determine the actual year a material was deposited or how long deposition lasted; it simply tell us which events came first.

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Cross-cutting relationships can also be used in conjunction with radiometric age dating to effect an age bracket for geological materials that cannot be directly dated by radiometric techniques.This means that a quartz sandstone deposited 500 million years ago will look very similar to a quartz sandstone deposited 50 years ago.Making this processes even more difficult is the fact that due to plate tectonics some rock layers have been uplifted into mountains and eroded while others have subsided to form basins and be buried by younger sediments.With out individual time stamps the process of dating these structures could become extremely difficult.To deal with many of these problems geologists utilize two types of geologic time: relative time and absolute time.Unlike relative time, absolute time assigns specific ages to events or formations and is typically recorded in years before present.This process requires much more sophisticated chemical analysis and, although other processes have been developed, often utilizes the decay rates of radioactive isotopes to determine the age of a given material.For example, if a fault were truncated by an unconformity, and that unconformity cut by a dike.Based upon such compound cross-cutting relationships it can be seen that the fault is older than the unconformity which in turn is older than the dike.The most obvious feature of sedimentary rock is its layering.This feature is produced by changes in deposition over time.


  1. Nov 7, 2015. faults that run through these layers of rock would instantly become the new youngest layer, as the layers that were pierced by the fault had to be there first. This picture sums it all up very well

  2. The Principle of Cross-Cutting Relationships states that rock formations that cut across other rocks must be younger than the rocks that they cut across. The same idea applies to fault lines that slide rock layers apart from each other; a fault that cuts across a set of strata must have occurred after the formation of that set.

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