Stratigraphy
층서학
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<speciesfyi-glossary slug="stratigraphy"></speciesfyi-glossary>Definition
The study of rock layers and layering to determine the relative ages of fossils and geological events.
Detailed Explanation
Stratigraphy's law of superposition holds that in undisturbed sequences, older layers lie below younger ones. Combining relative dating from stratigraphy with absolute dating from radioactive isotopes (such as uranium-lead or potassium-argon) gives fossils both sequence and age. Biostratigraphy uses characteristic fossil assemblages to correlate rock layers across continents — essential for understanding ancient geography and the history of life.