Contents of 7.3 How do geologists determine the relative ages of rocks in widely separated places?

Diagram showing a variety of fossils and how their placement in sedimentary rock can help date the rock.

7.3 How do geologists determine the relative ages of rocks in widely separated places?

Principle of Faunal Succession - William Smith (c. late 1700s to early 1800s) noted that limestones bounding coal layers contained different fossils.
Furthermore, he noted that these layers and fossils held true in other mines

Text Box: Therefore, the principle states Fossils of related organisms change in the same fashion in progressively younger rocks every place they occur. Fossils of different organisms first appear at different times. Fossil species disappear from the rock record everywhere when they become extinct and do not reappear in younger rocks.

Therefore, the principle states

Fossils of related organisms change in the same fashion in progressively younger rocks every place they occur.

Fossils of different organisms first appear at different times.

Fossil species disappear from the rock record everywhere when they become extinct and do not reappear in younger rocks.