
The oldest sedimentary rocks of Britain, called the Primitive Series, were subdivided into the Cambrian and Silurian by Adam Sedgwick and Roderick Murchison, respectively. We talked in late February about the controversy those two friends became embroiled in over which rocks were in which period, a 40-year-long argument that was finally settled by the establishment of the Ordovician Period, also named for a Welsh tribe.
—Richard I. Gibson
Map from Wikipedia, used under GNU free documentation license.
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