Athena Review Image Archive ™
Smith's Index Fossils (1816)
Index fossils for an upper chalk strata mapped in Britain (Smith 1816, tab.3).
William "Strata" Smith (1769-1839) was an English mining engineer and geologist who accurately mapped geological strata throughout Britain and first defined many index fossils. Smith began work as a surveyor’s apprentice around the coal mines of Devonshire in the 1780s, and in the 1790s supervised a six-year project to dig the Somerset Canal in southeast England.
As
sections were dug through the local rocks such as limestone, sandstone,
or shale along the canal routes, Smith noticed that certain layers of
rock consistently contained similar fossils, and that these varied
predictably from top to bottom. This revealed to Smith the essence of
stratigraphy, or the study of geological layering. In his own words,
“each stratum contained organized fossils peculiar to itself, and
might, in cases otherwise doubtful, be recognized and discriminated
from others like it, but in a different part of the series, by
examination of them.”
Smith saw that the strata thus in
themselves held the key for comparisons between fossil beds, which
Smith called “the principle of organic succession.” A sequence of
specific fossils (representing types or species of ancient life)
were directly linked with specific types and layers of rock, also
identifiable as a sequence, which could then be defined as an organized
formation.From
the 1790s onward, Smith created a series of geologic maps throughout
the counties of England and Wales, leading to the first accurate
description of geological formations throughout Great Britain. These
maps he published at his own expense in 1815.
Smith also published, the following year, an illustrated guide to the index fossils of each geological stratum described in the maps. This figure, showing fish and marine invertebrate fossils, depicts the index fossils for a Mesozoic chalk layer.
References:
Smith, William 1816. Index Fossils for Geological Map of England and Wales.
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