Deduce youngest rock layer from fossil dating
Cross-cutting relationships is a principle of geology that states that the geologic feature which cuts another is the younger of the two features. It was first developed by Danish geological pioneer Nicholas Steno in Dissertationis prodromus (1669) and later formulated by James Hutton in Theory of the Earth (1795) and embellished upon by Charles Lyell in Principles of Geology (1830).
Cross-cutting relationships may be compound in nature.
William Smith was one of the most important scientists from this time who helped to develop knowledge of the succession of different fossils by studying their distribution through the sequence of sedimentary rocks in southern England.
It wasn't until well into the 20th century that enough information had accumulated about the rate of radioactive decay that the age of rocks and fossils in number of years could be determined through radiometric age dating.
In other words, these relationships have various scales.
A cartographic crosscutting relationship might look like, for example, a large fault dissecting the landscape on a large map.
For example, if a layer of sediment containing a fossil of interest is bounded on the top and bottom by unconformities, where the lower unconformity truncates dike A and the upper unconformity truncates dike B (which penetrates the layer in question), this method can be used.
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.
Cross-cutting relations can be used to determine the relative ages of rock strata and other geological structures.
Explanations: A – folded rock strata cut by a thrust fault; B – large intrusion (cutting through A); C – erosional angular unconformity (cutting off A & B) on which rock strata were deposited; D – volcanic dike (cutting through A, B & C); E – even younger rock strata (overlying C & D); F – normal fault (cutting through A, B, C & possibly E).
BACKGROUND INFORMATION: Sedimentary rocks form in layers.
These layers were once environments as the Earth's surface.
The cylinder of rock is called a core and tells what the layers of rock are like at that one point on Earth.