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Steno formalized the laws of superposition, original horizontality, original continuity and inclusions in his publication entitled states that any inclusion is older than the rock that contains it.Steno's idea that fossils are older than the rock in which they are found hints at this principle, but Hutton is most often given credit for this principle.states that fossil organisms succeed one another in a definite, irreversible, and determinable order.The unconformity consists of many vertical tilted layers of grey shale overlaid by many layers of horizontal red sandstone.Playfair later commented that, "the mind seemed to grow giddy by looking so far into the abyss of time." Mc Phee (1998) points out that Hutton removed humans from a specious place in time just as Copernicus had removed humans from a specious position in the universe (p. Hutton gives us three more laws to consider when seeking relative dates for rock layers, one of which, the law of inclusions was described earlier.states any feature that cuts across a rock or sediment must be younger than the rock or sediment through which it cuts.This law was independently discovered by William Smith (1769-1839), a British engineer, while working on excavations for canals in England (Winchester, 2002 p.131) and by Georges Cuvier (1769-1832), a French anatomist, and Alexandre Brongniart (1770-1847), a French naturalist and geologist, during their work on the deposits of the Paris Basin.But the faults do not appear to continue into the coal seam, and they certainly do not continue into the upper sandstone.So we can infer that coal seam is younger than the faults (because it disrupts them), and of course the upper sandstone is youngest of all, because it lies on top of the coal seam.
In 1788 John Playfair came to see Hutton’s Unconformity in Inchbonny.
The realization that sediments turn into rock was counter to the view that all rocks on Earth formed in a single creation event.
Once Steno recognized that the fossils he was contemplating (sharks teeth and sea shells) were formed in the sediments of oceans he was able to work out the basic rules of stratigraphy.
An example of this is given in Figure 8.7, which shows three different sedimentary layers.
The lower sandstone layer is disrupted by two faults, so we can infer that the faults are younger than that layer.
There are a few simple rules for doing this, some of which we’ve already looked at in Chapter 6.