GEOL 3000 Geologic Maps Determining the Relative and Absolute Age of Map Units Relative Age Dating Superposition Up isn t always Younging Up Indicators Graded Bedding Pillowed Lavas mygdaloidal Zones in Lavas Ripple Marks Cross bedding Sedimentary Facies Time Trangressive Units Paleogeography of Middle Laurentia in the Paleozoic Advanced Transgression Regression Paleozoic Formations of the Upper Midwest Principles of Faunal Succession and Faunal Assemblage Index Fossils Widespread distribution Restricted known time of existence Common to many environments The Jordan Sandstone Unconformity Missing Fossils Gaps in the Geological Record Unconformities Siccar Point Scotland The mind seemed to grow giddy looking so far into the abyss of time John Playfair Illustrations of Huttonian Theory 1809 Creating Unconformities Nonconformity Angular Unconformity y Disconformit Grand Canyon Stratigraphy Unconformities or Pinch outs Gaps in the Minnesota Timescale Regional Correlation of Units Piecing the Rock Record Together Relative Time for Intrusive Igneous Rocks Principle of Cross cutting Relationships Global Time Markers Volcanic Ash Eruptions Global Time Markers Meteor Impacts K T Boundary mudstone impact layer coal K T impact site The 1 875 Ga Sudbury Impact The First Major Extinction Event Global Time Markers Magnetic Reversals Global Time Markers Climate Change Absolute Age Determinations Radiometric Dating Radioactive Isotopes Radioactive Decay Radioactive Decay Half life Zircon ZrSiO4 U substitutes for Zr but Pb does not Rb Sr Dating of a 87 86 Rb 87Sr Granite Sr is stable Rb chemically substitutes for K Sr chemically substitutes for Ca 87 Isochron t 2 t 1 Sr 86Sr 87 Metamorphism at t 1 Sr 86Sr m 87 t 0 Sr 86Sr 87 Rb 86Sr Ca plagioclase Granite whole rock K feldspar Biotite K rich
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