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

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