ANTH 18630 Lecture Notes - Lecture 19: Mesozoic, Paleozoic, Cladistics
30 Oct 2018
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Document Summary
Geological time, relative and absolute dates, radioactive decay, isotopes of oxygen can help reconstruct past climates and habitats, isotopes of carbon can help reconstruct past habitats and diets. 2 pangea"s where continents were together and then separated. Placental mammals by late mesozoic (70 mya) Buried in sediment, mineralized, exposed by tectonic processes. Reconstruct habitat, what did the animal eat. Often used together with relative dating techniques. When is melts, it releases 40- ar which cools and traps 40- ar gas. With time, 40- ar builds up and 40- k decreases. When atoms decay, they form stable daughter element (ex. Decay rates are uniform and occur at constant exponential or geometric rate. Measure ratio to parent element to daughter element using half life. Cosmic rays from sun hit nitrogen 14 atom in atmosphere, converting it to carbon 14 which combines with oxygen to form radioactive carbon dioxide. Absorbed by plants and gets into food chain.
