GEOL 1020 Lecture 5: EARTH HIST LEC. 5
7 Dec 2017
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Document Summary
Fossils often provide better, more accurate correlation than radiometric dating. Fossils are more common than radioactive elements in sedimentary rocks, whereas most minerals that can be dated by radiometric techniques are igneous. There is a range of uncertainty with radiometric ages. For rocks older than 1. 5 billion years old, the primary means of dating them would be isotopic dating. Prior to 1. 5 ga (or late precambrian), there are few fossils that are well enough preserved and easily identified to be index fossils. Sedimentary rocks comprise 75% of the earth"s rock record. Contains fossils -- the primary means of determining age. Enable geologists to reconstruct ancient environments and paleogeography. Provide a framework for interpreting life in the past. Contain natural resources such as fossil fuels (oil, gas and coals). A body of rock or sediment with a specific set of characteristics that represents a particular depositional environment .
