EAES 101 Lecture Notes - Lecture 23: Metamorphic Rock, Stratigraphic Column, Zircon
27 Oct 2016
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Absolute age dating and a quick trip through geologic time. Iclicker: which is the oldest: c) granite. Half-life to age: start with 100% parent, need to convert from life to real time, t for 14c=5730, 1 half-life=5730 years, 2 half-life=11470. Iclicker: you date a zircon grain in a sedimentary rock and find that it is 1. 7 billion years old (1,700,000,000). Radioactive dating: estimate the age of organic materials (wood) up to ~62,000 b. p, living organisms contain 14^c in equilibrium with atmosphere until time of death, 14^c decays to 14^n, life of 5730 years. Other numerical dating techniques: numerical ages are possible without isotopes, growth rings-annual layers from trees or shells, rhythmic layering-annual layers in sediments or ice. The geologic time scale: a composite stratigraphic column can be constructed, assembled from incomplete sections across the globe, it brackets almost all of earth history. Iclicker: which of these eons is the oldest: d) hadean.
