An introduction to geological structures and maps / Введение в геологическое картирование и геологические структуры

The onset and rapid spread of canals across the face of Britain in the late eighteenth century, closely followed by the building of the railway network in the early nineteenth century, were largely responsible for making the study of the strata, or stratigraphy, a subject of both practical and economic value. It is not surprising, therefore, that it was a land surveyor and canal engineer, William Smith (1769–1839), working initially in southern and eastern England, who first worked out that rock strata were not randomly disposed around the country but arranged in a definite order. He recognised  that sedimentary rocks, ‘the sediments ofpast ages’, first identified as such by James Hutton (1726–1797), are laid down with the oldest sediments at the base of the sequence and progressively younger beds resting on top. This was defined as the Law of Superposition (Fig. 1.1), and led to Smith being called ‘Strata Smith’ by his contemporaries. His work, particularly in the Cotswold Hills on the construction of new canals, led him to observe that each particular stratum of rock yielded its own distinctive assemblage of fossils. In addition, these fossil assemblages always occurred in the same order in different parts of the country. Furthermore, in some parts of the country, the rock type or lithology might change but parts of hisrecognised fossil assemblages remained and therefore the rock strata could be correlated despite the lithological variations. <...>