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Unformatted text preview: A typical rock formation Relative dating: some principles to follow... 1 Principle of superposition 2 Principle of original horizontality 3 Principle of lateral continuity 4 Principle of cross-cutting relationships 5 Principle of inclusions 6 Huelsenbeck Lecture 14 Slides page 1 of 11 Principles of unconformities (missing time) 7 Radiometric Age Dating • Uses unstable isotopes of naturally occurring elements. The isotopes decay: they change into different elements or different isotopes of the same element. • The rate of decay is known (has been measured in the laboratory) for a variety of isotopes. • When igneous rocks form, there is 100% parent and 0% daughter isotopes in the rock. • The ratio of the parent and daughter isotopes can be measured using a mass spectrometer. 8 9 Method Parent isotope Daughter isotope Half life Dating range Rubidium- strontium Rb-87 Sr-87 47 by 10m-4.6b Uranium-lead U-238 Pb-206 4.5 by 10m-4.6b Uranium-lead U-235 Pb-207 71.3 my 10m-4.6b Thorium-lead Th-232 Pb-208 14.1 by 10m-4.6b Potassium-argon K-40 Ar-40 1.3 by .1m-4.6b Carbon-14 C-14 N-14 5730 y 100-100,000 10 1999 GEOLOGIC TIME SCALE CENOZOIC MESOZOIC PALEOZOIC AGE (Ma) EPOCH AGE PICKS (Ma) MAGNETIC POLARITY PERIOD HIST. ANOM. CHRON. 5 10 15 20 25 30 35 40 45 50 55 60 65 QUATER- NARY PLEISTOCENE MIOCENE OLIGOCENE TRIASSIC JURASSIC CRETACEOUS PERMIAN DEVONIAN ORDOVICIAN SILURIAN MISSISSIPPIAN PENNSYLVANIAN CAMBRIAN* CARBONIFEROUS EOCENE PALEOCENE PLIOCENE PIACENZIAN L 0.01 1.8 3.6 5.3 7.1 1 .2 14.8 16.4 20.5 23.8 28.5 33.7 37.0 41.3 49.0 54.8 57.9 61.0 65.0 E L E L M E L M E E L ZANCLEAN MESSINIAN TORTONIAN SERRAVALLIAN LANGHIAN BURDIGALIAN AQUITANIAN CHATTIAN RUPELIAN PRIABONIAN BARTONIAN LUTETIAN YPRESIAN DANIAN THANETIAN SELANDIAN CALABRIAN HOLOCENE TERTIARY PALEOGENE NEOGENE 1 C1 C2 C2A C3 C3A C4 C4A C6 C6A C6B C6C C7 C8 C9 C10 C1 C12 C13 C15 C16 C17 C18 C19 C20 C21...
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This note was uploaded on 05/13/2009 for the course BIO 1B taught by Professor Carlson,mischel,power during the Spring '07 term at Berkeley.
- Spring '07