Fossil sequences

1815 Fossil sequences

The book of science

Tom Sharp

William Smith stratigraphy Fossil sequences

Fossil sequences

William Smith, surveyor and civil engineer, independently discovered and first illustrated how fossils can be used to identify geological strata under the fields and pastures, valleys, hills, and mountains. Carefully documenting layers of sediments in the channels of the new canals, coal pits, road and railway cuttings, quarries and escarpments, identifying rock outcrops, their inclinations and distributions, and matching them up according to the fossils in them, Smith was able to map actual strata and predict the rest over large areas of England, Wales, and parts of Scotland. He published one of the earliest detailed large-scale geological maps, The Geological Map of England and Wales showing “the courses and continuity of the strata in their order of superposition.”

Peculiarities of the strata

Strata of the plains London clay, forming Highgate, Harrow, Shooters, and other detached hills, identified by Volutæ, Rostellariæ, Fusus, Natali, Teredo, Crabs Teeth, and bones producing Septarium from which Parker’s Roman Cement is made Clay or Brickearth, with interspersions of sand and gravel, then sand and light loam upon a sandy or absorbent substratum, identified by Murices, Turbo, Pectunculus, Caria, Venus, and Ostreæ producing an abundance of materials which make the best bricks and tiles in the island Strata of the Chalk Hills identified by various Plagiostoma Chalk whose upper part is soft, containing flints (the best road materials), identified by Alcyonia, Ostreæ, and Echini and whose under part is hard containing no flints but good lime for water cements, identified by Terebratulæ Teeth, and Palates producing potters clay, glass-grinders sand and loams and sands used for various purposes underlain by Green sand, parallel to the Chalk, identified by Funnelform, Alcyonia, Venus, Chama, Pectines, Terebratulæ, and Echini producing firestone and other soft stone sometimes used for building Strata of the Clay Vales Brickearth—Blue Marl, “so kindly for the growth of oak as to be called in some places the oak-tree soil,” identified by Belemnites and Ammonites Portland rock—Purbeck Stone, Kentish Rag, and limestone of the vales of Pickering and Aylesbury identified by Turritella, Ammonites, Trigoniæ, Pecten, and Wood producing the first quarry and building stone downward in the series and Kimmeridge coal Oaktree Clay—Iron sand and Carstone, which in Surrey and Bedfordshire identified by Trochus, Nautilus, Ammonites in masses, Osteæ (in a bed), and bones Coral Rag and Posolite—Iron Sand and Carstone, which contains Fuller’s Earth in Surrey and Bedfordshire, and, in some places, Yellow Ochre and Glass Sand identified by various Madreporæ, Melaniæ, Ortreæ, Echinie, and spines underlain by sand Clunch Clay and Shale, and Kelloways Stone, a dark blue shale producing a strong clay soil chiefly in pasture in North Wilts and the Vale of Bedford identified by Belemnites, Ammonites, and Ostreæ Strata of the Stonebrash Hills Cornbrash, a thin rock of limestone chiefly arable and lying in clay identified by Modiola, Cardia, Ostreæ, Avicula, and Terebatulæ which makes tolerable roads Sand and sandstone, and then Forest Marble, in thin beds used for rough paving and slating identified by Pectines, teeth, bones, and wood Clay over the Upper Oolyte identified by Pear Encrinus, Terebatulæ, and Ostreæ, Upper Oolyte, or Great Oolite Rock, which produces Bath Freestone identified by Madreporæ Fuller’s Earth and Rock identified by Madiolæ and Caria Under Oolite, of the vicinity of Bath and the midland counties identified by Madreporæ, Trochi, Nautilus, Ammonites, and Pecten sand identified by Ammonites, Belemnites, as in under Oolite and Marlstone identified by numerous Ammonites the Oolite providing the finest building stone in the island for Gothic and other architecture that requires nice workmanship Strata of the Marl Vales Blue Marl, under the best pastures of the midland counties identified by Belemnites and Ammonites in mass Lias—Blue Lias and White Lias identified by Pentacrini, numerous Ammonites, Plagiostoma, Ostreæ, and bones Red Marl and Gypsum, soft sandstones and salt rocks and springs Strata of the Coal Tract Redland limestone—Magnesium limestone and soft sandstone identified by Madreporæ, Encrini in masses, and Producti producing small quantities of copper, lead, and colamine Coal Measures—rocks and clays with accompanying coal, generally with a sandstone beneath identified by numerous vegetables, ferns lying over the coal Strata of the mountainous country identified by Madreporæ, Encrini in masses, and Producti Trilobites Mountain Limestone—Derbyshire Limestone or Metalliferous Limestone Red Rhab and Dunstone of the Southern and Northern Parts with interspersions of limestone producing lead, copper, calamine, and marble Killas or slate and other strata of the mountains on the west side of the island with interspersions of limestone polished for marble, producing tin, copper, lead, and other minerals Granite, Sienite, and Gneiss producing the most durable building stone in the island for bridges and other heavy works

Hidden sediments

Mounds in middle-eastern deserts reveal layer under layer of decomposed cities. Rushing noisily upon the face of this planet our civilization deposits its broken riches. As I cross this city on a diesel bus I think about what’s under the streets under the electric, cable, water, gas under the sewers and storm drains. There lay the compressed layers of pre-historic baylands hillside runoff ancient marine beds broken pieces of extinct volcanos resting in their quietnesses.

William Smith was a surveyer and civil engineer, but he is best known for his work as a geologist. He is known as the founder of stratigraphy the father of English geology, but he was recognized for his work only late in life.

Working at Mearns Pit at High Littleton, part of the Somerset coalfield, Smith took an interest in the inclination and succession of strata and surmised that the pattern could be traced eastward and northward across England. His subsequent work as an surveyor's assistant and as an employee of the Somersetshire Coal Canal Company, and later his travels in his private practice as an engineer gave him opportunity to learn more. He was the first to correlate each strata with the fossils that it contained, or as he wrote, the “fossils peculiar to itself.” He published the first large-scale geological map of Britain.

“Peculiarities of the strata” is a title of one of Smith's illustrations, from which the whole of this poem borrows names of strata and fossils and descriptions of materials produced from the strata. Many of the names of the strata were invented by Smith and are still in use today. The layered details above represent Smith’s great breadth of geological knowledge.

I have always been fascinated by glimpses of the masses that underly the surface of this land on which we build and plant.

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