Document Type

Article

Publication Date

2016

Abstract

Until the 19th century, the rocks exposed throughout the provinces of Devonshire and Cornwall in southwestern England had long been considered to be Carboniferous in age because of their content of fossil plants. Closer investigation by Murchison and Sedgwick in 1836, however, showed that only the uppermost portion of these rocks contained fossil plants. Because the lower portion of the rock sequence was devoid of plant fossils, was highly deformed, and resembled the rocks of northwest Wales which they had recently studied, Murchison and Sedgwick assigned the rocks to the Cambrian System. However, local fossil collectors had submitted fossil corals collected from this same interval to Professor William Lonsdale who found them to be intermediate in evolutionary development between the corals of the Silurian and those of the Carboniferous. Based on this observation, Lonsdale suggested that this section of rock might be correlated with the Old Red Sandstone, a thick sequence of sandstones and shales located stratigraphically below the Carboniferous throughout much of Great Britain. It took two years before further study convinced Murchison and Sedgwick that Lonsdale was correct in his interpretation; it was Lonsdale who proposed the name Devonian for the system of rocks that existed between the Silurian and the Carboniferous. Unfortunately, the Devonian rocks in Great Britain are highly deformed by folding and faulting and are therefore very difficult t􀀞 decipher. Perhaps the best sequence of Devonian rocks in the world are located in New York.

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