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Unformatted text preview: Chapter 2 20:41 William Smith • Hired to find the best route for a canal for coal barges-discovered fossil and that each stratum not only extended invisibly beneath the farms in the distance but also maintained its place in the vertical succession of rock layers. How are fossils formed • Plants and Creatures dead or living are covered in sediment (silt, mud, debris etc) • For preservation of soft parts quick burial is needed Niels Stensen a Danish physician formulated three basic principles of historical geology from observing sedimentary rock: (3 principles are basic to the geologic specialty of stratigraphy the study of layered rocks.) • Superposition • Original horizontality • Original lateral continuity • Principle of superposition • States that in any sequence of undisturbed strata, the oldest layer is at the bottom, and successively younger layers are successively higher. • Does not always work because layers can be steeply tilted or overturned. In these situations geologists must look for clues in recognizing their lowermost and uppermost layers. Principle of original horizontality • States that sediment is deposited in layers that are originally horizontal Principle of original lateral continuity • States that a rock layer extends continuously in all directions until it thins out or encounters a barrier John Strachey •...
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- Fall '09
- Geology, William Smith, Original Lateral Continuity