"It´s all there locked in the stone,
the truth is told in fossilized bone."
"Fossils
have been long studied as great curiosities, collected with great
pains, treasured with great care and at a great expense, and shown and
admired with as much pleasure as a child's hobby-horse is shown and
admired by himself and his playfellows, because it is pretty; and this
has been done by thousands who have never paid the least regard to that
wonderful order and regularity with which nature has disposed of these
singular productions, and assigned to each class its peculiar stratum."
William Smith, notes written January 5, 1796
William
Smith was born March 23, 1769 in the village of Churchill, in the
county of Oxfordshire, into a respectable farming family. His father
died when he was seven, so his mother brought him to the farm of his
uncle.
And just here the young William makes an encounter that
will change his life. In these parts of Oxfordshire, for the “long
pound” - a weight standard of ca. 600g - are used not
the common iron weights, but strange rounded stones. They are commonly found in the nearby
quarries. Smith is fascinated of this stones - why they resemble the sea
urchins, that he has seen in the books or on the coast of the sea,
distant more then 160 kilometers from the place where they are now
found? If these are remnants of animals, why are they petrified. Why
some of them resemble animals that no scholar has ever seen? Puzzled
by this mystery, he starts to collect minerals and fossils. He
is an enthusiastic autodidact; studying the landscape he quickly learns
geometry, surveying and mapping, hydraulics and
hydrology.
At the age of eighteen he became an
assistant surveyor, learning his trade from the master surveyor Edward
Webb. Surveying required Smith to travel all over England; in 1794 and
following years he toured the entire country. Detailed maps were essential to plan and
construct streets and canals for the industrial revolution - good surveyors were requested workers.
Here
Smith can apply his knowledge, the job of surveying canal routes
requires detailed knowledge of the rocks through which the canal was to
be build.
In 1792 he works for the rich coalmine owner Elisabeth
Jones in Somerset. He lives in a property of the lady –
Rugbourne Farm - that he will later call the birthplace of his geology,
because of his habit to sit in a niche of the house and study his rocks.
He notes that the coal-bearing layers are over- and underline by a
characteristic succession of sandstones and marls. Always is the coal
formation overlain by marine and then non-marine rocks. Always is
the coal stratum underline by a grey clay – the ancient soil on which
the coal forming giant ferns and horsetails grown, millions of years
ago.
Even more important, Smith observed that the fossils found in a
section of sedimentary rocks were always in a certain order from the
bottom to the top of the section. This order of appearance could also be
seen in other rock sections, even those on the other side of the British island - maybe on the entire world there is a certain order of strata and whoever can read it will quickly discover the coal-formation – the black gold of the
18th century.
".
. . each stratum contained organized fossils peculiar to itself, and
might, in cases otherwise doubtful, be recognised and discriminated from
others like it, but in a different part of the series, by examination
of them"
This
is the statement of the "principle of faunal succession": The layers of
sedimentary rocks in any given location contain fossils of a definite
age in a definite sequence; the same sequence can be found in rocks
elsewhere and hence the strata with the same fossils can be
correlated between various locations.
The principle of deposition, a stratum
that lays below in a succession is older, and vice versa, was not new.
But Smith was the first to proof this hypothesis by using
guide fossils. Geological maps before Smith mapped and catalogued rocks
by their inorganic characteristics - like sandstones, marls and chalks. Still
further differentiation was only possible maybe by colour or other minor
properties. This classification was very restricted and it showed no
apparent pattern. Smith discovered and applied an ulterior classification scheme, a scheme that can
differ rocks with no doubt, even if they look very similar.
Fig.2. Ammonites, characteristic fossils for the Mesozoic and the most appreciated fossils by Smith.
In 1816 he publishes his observations in form of a book and a map, describing for ever strata of the United Kingdom the characteristic fossils:
Fig.3. A
diagram of 1888, showing the sequence of strata and their
characteristic fossils. Notice that at this date, the recently proposed
Ordovician (1878) System had not yet been accepted, nor the Paleocene
(1874) or Oligocene (1854) as epochs of the Cenozoic. Instead of
“Precambrian” or “Primary” this scale uses the term “Laurentian”, since
the studies of Precambrian rocks had made the most progress in the
Laurentian region of the Canadian Shield.
Bibliography:
SMITH,
W. (1816-1819). Strata identified by organized fossils, containing
prints on coloured paper of the most characteristic specimens in each
stratum. London: W. Arding.
WINCHESTER, W. (2001). The Map that Changed the World: William Smith and the Birth of Modern Geology. New York: Harper Collins.
