EARTH121 Chapter Notes - Chapter 8: Cenozoic, Radiometric Dating, Radiocarbon Dating
2 Sep 2016
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Numeric date required, finally obtained after our understanding of radioactivity. Relative dating rocks placed in their proper sequence of formation. Cannot tell us how long ago something took place, only that it followed one event and preceded another. Law of superposition each bed in a sedimentary rock is onder than the one above it and younger than the one below. Law of original horizontality layers of sediment are generally deposited in a horizontal position. If rock layers are still flat they have not been disturbed and they still have their original horizontality. If the layers are folded or inclined at a steep angle they must have been moved by crustal disturbances after their deposition. Law of cross-cutting relations when a fault cuts through other rocks or when magma intrudes, the fault or intrusion is younger than the rocks affected and occurred after deposition. Inclusions fragments of one rock unit that have been enclosed with another.
