Suppose you find a fossil at one place that cannot be dated using absolute methods.That fossil species may have been dated somewhere else, so you can match them and say that your fossil has a similar age. Geologic Principles to determine relative age of rocks II. Principle of original horizontality – sedimentary layers or lava flows were originally deposited horizontally c.
Throughout the history of life, different organisms have appeared, flourished and become extinct.
Many of these organisms have left their remains as fossils in sedimentary rocks.
Some of the most useful fossils for dating purposes are very small ones.
For example, microscopic dinoflagellates have been studied and dated in great detail around the world.
Law of cross cutting relations –any feature that cross cuts a sedimentary body of rock is younger i.
Law of inclusions – any piece of rock that becomes incorporated into a newly forming rock is older than the new rock f. The Permian through Jurassic stratigraphy of the Colorado Plateau area of southeastern Utah is a great example of Original Horizontality and the Law of Superposition, two important ideas used in relative dating.These strata make up much of the famous prominent rock formations in widely spaced protected areas such as Capitol Reef National Park and Canyonlands National Park. Law of superposition – if deposits are undisturbed, the oldest is on the bottom and the youngest is on the top e. Law of lateral continuity – deposits extend laterally until they pinch out and run out of material d. Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence.