Karina OrozcoChapter 9 Lectured Notes – Telling Geological TimeTelling Geologic Time-Relative Dating: determining the relative sequenceof geologic events (rock record).-Absolute Dating (numerical): determining the absolute ageof geologic events (timerecord).The geologic time scale“Calendar” of Earth history divides geologic history into units created using relative datesStructure of the geologic timescale~ Eons-Phanerozoic (“visiblelife”)the most recent eon,began about 540 millionyears ago-Proterozoic-Archean-Hadean– the oldest eon~ Era subdivision of an eon-Eras of the Phanerozoic eon-Cenozoic (“recent life”)-Mesozoic (“middle life”)-Paleozoic (“ancient life”)-Eras are subdivided intoperiods (Periods aresubdivided into epochs)~ Divisions in the worldwide stratigraphic column use variations in fossils~ Built using a combination of paleontology, stratigraphic relationships, cross-cuttingrelationships, and absolute (isotopic) agesRelative Dating:-Law of Superposition-Principle of Original Horizontality-Principle of Cross-Cutting Relationships-Principle of Faunal Succession-Significance of Inclusions-Unconformities
