04 Geologic Time

04 Geologic Time - buried Index fossils Good index fossils...

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(D) Geologic Time Relative Dating: to place a sequence of events in the proper order Law of Superposition, Law of Original Horizontality, Law of Lateral Continuity Time-breaks may exist in the form of unconformities Fossils also play a role in the determination of relative ages Once the basic sequence of fossil forms in the rock record is determined, rocks can be placed in their correct relative chronological position on the basis of the fossils contained in them In turn, if one finds exactly the same type of fossil organism presented in 2 rocks, these rocks must be of the same age Disadvantage: Fossilization may occur long after the organism is dead and
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Unformatted text preview: buried Index fossils Good index fossils are those derived from particular plant or animal species that were distributed widely over the earth but existed for a very limited period of time Easily identified/recognized, readily preserved • Radioactive carbon dating (radiometric dating): capable of assigning more precise dates rather than relative ages • The Geologic Time Scale (refer to Notes p.2) Phanerozoic Eon — encompassed all that span of time from which fossil remains were known Precambrian Eon — All of the relatively unfossiliferous rocks older than the Cambrian period...
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