Hugh S. Torrens

Some personal thoughts on stratigraphic precision in the twentieth century

Abstract Surprisingly, most of the major elements of today’s stratigraphic column were in place by 1850. By then, the ideas that stratigraphy concerned geological time relations, and that a palaeontological identity of ‘best’ fossils (like ammonites) was an indication of time-equivalence, were starting to be accepted. By 1900, thanks to the work of people like Henry Shaler Williams (USA) and Sydney Savory Buckman (UK) stratigraphy was starting to concern itself with the precision with which biochronological time-scales could be created, especially in the Jurassic. By then, Buckman had demonstrated the great extent to which particular lithologies could cross time-lines and equally how well such rapidly evolving fossils as ammonites could be used to discriminate time. But from 1960, facing new demands for energy, and the growth of new ‘earth science’, focussing on numerical methods in geophysics and geochemistry using computers, such field-based ‘historical geology’ was progressively perceived as boring, out-dated, and expensive. Many new techniques, which ignored, or worse, assumed time-equivalence, now evolved. Fossils by their unique nature had given unique signatures to discriminate time. But some of the new methods relied on binary repetitions, not unique to time, and may suggest a false precision. This paper attempts a, now near-impossible, investigation of the temporal precisions that stratigraphic methods, both old and new, might attain. It concludes that we need to pay greater attention to the incompleteness of the stratigraphic record and to the chronological precision with which we can investigate that record. It now seems almost axiomatic that the harder you look at a rock the more incomplete the record of its stratigraphy appears to become.

From d’Orbigny to the Devonian: some thoughts on the history of the stratotype concept

Abstract D’Orbigny’s stratigraphic contributions were enormous, both practical and theoretical. In his practice, d’Orbigny realised the central importance of using fossil faunas to correlate strata across different countries. His ‘ succession chronologique des âges du monde ’ (of 1852) recognised 5 periods and 27 stages (ignoring his ‘ epoque actuelle ’). The great majority of the latter were from two Periods, Jurassic (stages 7 to 16) or Cretaceous (17 to 23). D’Orbigny described the palaeontological characteristics, and geographical extensions, of each. Some stages he based on countries he never visited and although he never specified ‘ stratotype ’ localities, he referred to some as ‘ etalon ’, ‘ le mieux ’ or ‘ le plus beau ’. These leads proved crucial when, in the mid 20th century, stratigraphers realised that definitions of chrono-stratal units must be attempted. The first attempts at typification simply followed zoology, where a type specimen tries to define a central position within the morphological variation of a species. In 1962, an early attempt was made to define Jurassic stages by three type horizons at different type localities (or stratotypes as they were now called) for each. A central horizon was chosen as ‘lectotype section’ and upper and lower boundaries for each were defined elsewhere. In France, it was preferred to investigate original intentions at named localities, through unit-stratotypes . These allowed some nationalistic pride, since France was the home of so many d’Orbignyan stages. 1980 saw the publication Les Etages francais et leurs Stratotypes . However, British Silurian stratigraphers had realised that such zoologically based concepts would produce conflict, when any defined upper boundary stratotype conflicted with the defined lower boundary of a superjacent unit. They suggested, from 1962, to define only lower boundaries, via ‘golden spikes’, at basal-boundary stratotypes . This was the method chosen for the basal Devonian stratotype at Klonk, Czech Republic, defined in 1972, and a method adopted globally from 1986. However, this was when correlations were still largely based on fossils. The explosion of so many other stratigraphies since, based on magnetic or chemical records, events etc, has produced a first reaction against the idea that such stratotypes should be so defined, while a second, potentially more major claim, is that any ‘golden spike’ concept may no longer ‘glitter’, as competing stratotype concepts may be holding back stratigraphic progress.

Timeless order: William Smith (1769–1839) and the search for raw materials 1800–1820

Abstract Smith first described himself as ‘land surveyor and drainer’ in his 1801 Prospectus but then as ‘engineer and mineralogist’ in his first book of 1806. His several careers are discussed with an attempt to shed new light on his pioneering career as ‘mineral surveyor’ (a term invented by his pupil, John Farey, in 1808). The trials for coal with which he was involved can be divided into two: those in which he used his new stratigraphic knowledge in positive searches for new coal deposits; and those where his stratigraphic science could often negatively demonstrate that many such searches were doomed to failure. These latter attempts were being made in, and misled by, repetitious clay lithologies, which resembled, but were not, Coal Measures. Smith was the first to show how unfortunate it was for such coal hunters that the British stratigraphic column abounded in repetitious clay lithologies. It was also unfortunate for Smith that many of the founding fathers of the Geological Society were unconvinced of the reality or the utility of Smith’s discoveries. Its leaders at first did not believe he had uncovered anything of significance and then simply stole much of it. The development of Smith’s stratigraphic science in the world of practical geology remains poorly understood, but the legacy of his method for unravelling relative geological time and space was one of the most significant of the nineteenth century.

Arthur Aikin's mineralogical survey of Shropshire 1796-1816 and the contemporary audience for geological publications

It has become almost traditional for historians of geology to claim that Roderick Murchison (1792–1871) ‘opened to view for the first time’ the fossiliferous rocks below the Old Red Sandstone which Murchison described in his monumental work The Silurian System published in 1839. Murchison himself claimed in the introduction to this work ‘no-one was previously aware of the existence below the Old Red Sandstone of a regular series of deposits, containing peculiar organic remains’. Professor John Phillips expressed the traditional view well when he wrote of the larger area of which Shropshire forms a part: ‘practically before the Summer of 1831 the whole field of the ancient rocks and fossils… was unexplored but then arose two men… Adam Sedgwick and Roderick Murchison and simultaneously set to work to cultivate what had been left a desert’. Against this we must set the statement of George B. Greenough (1778–1855), first president of the Geological Society of London, as reported in 1841. He had ‘frequently expressed a conviction, as a result of his own observations…, that adequate enquiry alone was wanting to prove the existence of a succession of strata in the west of England, and in Wales—not less regular than that which had been demonstrated in the centre and east of the Island.’

Dissenting science: the Quakers among the Founding Fathers

Abstract Only three of the 13 founding members of the Geological Society of London were Quakers: William Allen and the brothers Richard and William Phillips. As dissenters, they sought to play a significant part in this new scientific development because they were in many ways excluded from English civil society. Such exclusion had encouraged their entry into trade and commerce, and they saw science as a means of improving the world and their place in it. Their great agitation against slavery, at its height just as the Geological Society of London was founded, significantly enhanced their coherence as a group. One of the first fruits of their interest in science was the Askesian Society, founded in 1796 by Allen and William Phillips, among others. With over half of its membership made up of Quakers, the Askesian was amongst the earlier of the London scientific societies. From its membership, in 1799, grew the British Mineralogical Society, which planned, by survey and analysis, to produce a mineral history of Britain. With Allen, and soon both Phillips brothers, involved in manufacture, analysis and lecturing in the field of chemistry, these interests inevitably led them to want to better understand, and use, mineral resources and to contribute to the founding of the Geological Society.

The Moravian minister Rev. Henry Steinhauer (1782-1818); his work on fossil plants, their first "scientific" description and the planned Mineral Botany

Abstract Henry Steinhauer (born in 1782 at Haverfordwest, UK; died in 1818 at Bethlehem, Pennsylvania, USA) was the son of a Moravian minister and teacher. He attended their Yorkshire school from 1789 and then trained for their ministry in Germany. He returned to teach at Fulneck from 1801 to 1811. Moravians particularly encouraged the study of, and participation in, music and natural history, and Fulneck school had a museum for the latter by 1795. At Fulneck Steinhauer came across the fossil plants found in nearby coal mines. By 1811 he was suffering from consumption. To improve his health he moved temporarily to London where he tried to encourage James Sowerby to undertake a ‘Mineral Botany’ project to parallel Sowerby’s one on fossil shells, Mineral Conchology. Sadly, this failed to come to fruition. Next Steinhauer moved to Bath, where he became a disciple of the stratigraphic methods of William Smith. In 1814 he received a call to teach at the new world Moravian settlement of Bethlehem in Pennsylvania, USA. He set off late in 1815 and there presented his only palaeobotanical paper to the American Philosophical Society in May 1817. This gave scientific descriptions of 10 species of English fossil coal plants and introduced valid binomial nomenclature for such fossils. His large collection of stratigraphically arranged fossils from all over England, and its detailed manuscript catalogue all predating his 1815 departure, survive in Philadelphia. His work has largely been lost sight of because of his early death and the tragic separation of this fine collection from its place of origin. He deserves to be better known.