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THE LANGUAGE OF THE EARTH – PART VII. Geochronology Methods for Determining the Relative and Absolute Age of Rocks. Relative Age Dating - Superposition. Principles of Faunal Succession and Faunal Assemblage. Index Fossils - Widespread distribution - Restricted, known time of existence
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THE LANGUAGE OF THE EARTH – PART VII Geochronology Methods for Determining the Relative and Absolute Age of Rocks
Principles of Faunal Successionand Faunal Assemblage Index Fossils - Widespread distribution - Restricted, known time of existence - Common to many environments
Global Time MarkersMeteor Impacts K-T Boundary mudstone-impact layer coal K-T impact site
Regional Correlation of UnitsPiecing the Rock Record Together
Radioactive Decay Half-life Zircon ZrSiO4 U substitutes for Zr, but Pb does not.
Rb-Sr Dating of a Granite 87Rb 87Sr; 86Sr is stable Rb – chemically substitutes for K Sr – chemically substitutes for Ca Isochron t=2 t=1 87Sr/86Sr Metamorphism at t=1 87Sr/86Sr°(m) t=0 87Sr/86Sr° 87Rb/86Sr Ca-plagioclase Granite whole rock K-feldspar Biotite (K-rich)