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USGS CMG InfoBank: Chronology On the Basis of Superposition

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Comment: 15:43 - 16:36 (00:53)
Source: Annenberg/CPB Resources - Earth Revealed - 10. Geologic Time
Keywords: "geologic time", "Principle of Superposition", "Dee Trent", correlation, Europe, fossil, superposition, chronology

Our transcription: The standard geologic time scale is based really on the law of superposition; the oldest rocks are on the bottom and the youngest rocks on the top.
Looking at rocks in various parts of Western Europe, it was recognized that certain formations could be correlated from one region to another, and the older rocks were very distinctive with a distinct group of fossils in them.
The younger rocks overlay the older ones, they had different colors, different characteristics, different fossils.
By arranging them sequentially, which ones were the oldest and which ones were the youngest, they were able to establish the chronology just on the basis of superposition.
Each of the rock units took a name from the organisms that were in it or the region where it was first studied giving us the modern geologic time scale.

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