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To ae or not to ae? Spellings of chronostratigraphic terms

The Geological Society of London (GSL) has resolved to adopt, for its own publications and communications, the spellings of high level chronostratigraphic units as given by the International Commission on Stratigraphy in its International Chronostratigraphic Chart. Previously, the GSL had followed preferred spellings as given in the Oxford English Dictionary (OED). This includes words like Paleogene versus Palaeogene, Paleozoic versus Palaeozoic, and Archean versus Archaean. Here, Paul Pearson of the GSL Stratigraphy Commission explains some of the reasoning behind  this decision and considers the history of these and other terms

  • Paul N. Pearson, on behalf of the Stratigraphy Commission of the Geological Society of LondonSchool of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT,

IN 1833, when Charles Lyell added the terms 'Eocene', 'Miocene', and 'Pliocene' to the geological lexicon (in the third volume of his famous Principles of Geology), he constructed them from Greek roots. Hence Eocene was from 'eos' (=dawn) plus 'kainos' = new or recent, meaning the dawn of the recent; Miocene was from 'meion' (= less + recent) and Pliocene was from 'pleion' (= more + recent). Citing other English words that are simplified from classical roots as precedents, Lyell remarked: "The Greek diphthongs ei and ai are changed into the vowels i and e, in conformity with the idiom of our language... I sincerely wish that the numerous foreign diphthongs, barbarous terminations, and Latin plurals, which have been so plentifully introduced of late years into our scientific language, had been avoided as successfully as they are by French naturalists" (Lyell 1833, p. 53, footnote).


Shortly after, on the coast of Patagonia, a young man serving as naturalist aboard HMS Beagle took delivery of this eagerly awaited tome and immediately began applying Lyell's classification to his own observations of sedimentary rocks. Like most of his contemporaries, Charles Darwin, had received an almost entirely classical education. Despite declaring himself a "zealous disciple" of the great geologist, he did not hesitate to correct the spelling to 'Meiocene' in his notebooks (Galvin, 1993). Indeed within about a year, the spellings 'Meiocene' and 'Pleiocene' were published (by Greenough, 1834) and when Lyell himself (1839) added the 'Pleistocene' to the list ('pleistos' + 'kainos' = most + recent), he spelt it that way, whereas 'Plistocene', although inviting mispronunciation, would have been more consistent with his method (as pointed out by Renevier, 1897; see Berggren, 1998, for further discussion).

Soon after, when John Phillips (1840, p. 157) first published the term 'Palæozoic' (and, incidentally, giving credit for the term to Adam Sedgwick) he did it with a ligature, that is, two letters joined together to indicate a diphthong (a diphthong, to be clear, is a double-vowel sound, not a piece of typography). Phillips introduced the term 'Kainozoic' at the same time based on the Greek root 'kainos' that Lyell had used to get his Latinized '-cene' endings, although he himself soon spelled it Cainozoic (Philips 1841, p. 60) and later Cænozoic, with a ligature (Philips 1860, p. 51)!


Figure 1. A forerunner of the geological timescale (Philips, 1841). Spellings of words like 'Cainozoic', 'Palæozoic', 'Pleiocene' and 'Meiocene' frequently varied in the nineteenth century.

The situation deteriorated further as can be seen, for example, in the sixth edition of Lyell's Elements of Geology (Lyell, 1865) where he retained his original spellings for 'Miocene', etc., accepted Phillips's ligature in 'Palæozoic' and rendered 'Cainozoic' thus. After that, Naumann (1866) coined his 'Paläogen' in a German publication, Schimper (1874) introduced his 'Paléocène' in a French one, and Van Hise (1892) added the 'Archean' in an American one.

Incidentally, Lyell's 'Miocene' was castigated by Henry Fowler in his influential Modern English Usage (1926, and still in print) who used it as the type example of a 'barbarism', describing it as "a typical example of the monstrosities with which scientific men in want of a label for something, and indifferent to all beyond their own province, defile the language. The elements of the word are Greek, but not the way they are put together, nor the meaning demanded of the compound". This may be unfair on Lyell who was clearly aiming for simplicity of spelling in English. Indeed 'Miocene' and the other terms had been suggested to him in correspondence by William Whewell (the person who coined another barbarous but undeniably useful word, 'scientist').


The various nations have, of course, long had a tradition of spelling their Greek derivations differently. In British English the usual practice for words with the root 'palaios' has been to use the spelling 'palaeo-', whereas 'paleo-' is considered American. Ligatures are seldom used nowadays but we have a tradition of using the digraph (double letter) 'ae' in their stead, as in 'Palaeogene' and 'Palaeozoic'. These are currently the preferred spellings in the Oxford English Dictionary (OED) and until recently were stipulated in author instructions issued by the GSL's publication house. Darwin's spelling 'Meiocene' and the similar 'Pleiocene' are not preferred in British English, although logically perhaps they should be.

It is worth noting that the term 'Paleocene' should be an exception even when rendered in British English because Schimper's word is clearly a contraction of 'palaeo' + 'Eocene', meaning the older part of Lyell's Eocene. In other words, its derivation is Pal-eocene not Palaeo-cene, which should, perhaps, also guide its pronunciation. Despite that issue having been clarified by Pulvertaf (1999), the etymology of 'Palaeocene' is incorrectly given in the OED as from 'palaeo' (old) + 'kainos' (new) and this spelling has been standard in British publications until now. Arguably, the only logically consistent way for us to retain the 'palaeo' spelling in this case would be to transcribe Schimper's epoch as the 'Palaeoeocene', a word with a wonderfully high vowel quotient. We hope readers of Geoscientist will keep this suggestion under their hats!

Phillips's 'Kainozoic' has variously been rendered 'Cainozoic', 'Cænozoic', 'Caenozoic' (as in the Natural History Museum's popular classic, British Caenozoic Fossils), and of course 'Cenozoic', all of which were in use by the mid-nineteenth century. The previous GSL style guide stipulated that 'Cenozoic not Cainozoic' is the British-preferred spelling, and indeed that is the how it is in the OED, although the reasoning behind that is not explained. Perhaps it is simply because the spelling 'Kainozoic' fizzled out during the twentieth century in the face of the inexorable rise of 'Cenozoic' following a proposal to harmonize it with Lyell's '-cene' terms as recommended at the influential International Geological Congress at Bologna in 1881 (Renevier, 1897). Interestingly, the spelling 'Plistocene', also favoured at that congress for reasons of harmonization, never caught on (Figure 2).


Figure 2. The spellings 'Pleiocene' and 'Meiocene' were never dominant and died out by 1890. 'Plistocene' made a brief appearance after the Bologna Congress of 1881 but, like a failed mutation, it never spread. 'Cenozoic' eventually won out over its competitors in the early twentieth century although 'Cainozoic' is still occasionally in use. Data: Google Books Ngram viewer.

One nomenclature

Looking back to the beginning, when the Geological Society of London was inaugurated at the Freemasons' Tavern in 1807, the luminaries present resolved "That there be forthwith instituted a Geological Society for the purpose of making geologists acquainted with each other, of stimulating their zeal, of inducing them to adopt one nomenclature, of facilitating the communications of new facts and of ascertaining what is known in their science and what remains to be discovered" (my italics). There are good reasons to adopt one nomenclature, and in the age of internet search engines and big data, this is arguably more so than ever before, and applies on a global scale.

The formal nomenclature of stratigraphy is the domain of the International Commission on Stratigraphy (ICS) which is affiliated to the International Union of Geological Sciences (IUGS). The ICS frequently updates the International Chronostratigraphic Chart, which is supposed to set the standard of communication worldwide (Cohen et al., 2013). There is an analogy to be drawn with SI units, which are intended to standardise international usage. British stratigraphers serve on many of the committees and subcommissions of the ICS. For better or worse the ICS consistently uses American English spelling (or International English, if one prefers) and there seems little prospect of that changing, hence we have 'Paleozoic', 'Paleocene', 'Paleogene', 'Archean'. The terms 'Paleoproterozoic'  and the doubly-affected 'Paleoarchean' complete the set of those words that, in British English, are generally spelled differently. Whatever else one might think of these spellings, they are at least consistent with each other (except 'Pleistocene', always the anomaly) and as simple as they can be.

Other nations issue their own translations of the International Chronostratigraphic Chart to show how these internationally accepted terms should be rendered when written in their own languages (for instance, the Paleozoic is Paléozoïque, Paleozoikum, Paleozoico and Paleotsooinen in French, Norwegian, Spanish and Finnish, respectively). Despite this diversity, nobody but the Brits, it seems, uses the 'ae' digraph. Hence we have a clear choice: we could issue a special UK chart bedding in the 'ae' spellings as official or we could opt to fall into line with the ICS.

The GSL Stratigraphy Commission (GSL-SC) is the UK platform for discussing stratigraphic terminology and usage. It has representation from academia, the British Geological Survey (BGS) and the GSL itself. The matter was discussed (at some length) and the GSL-SC voted on the motion:

"The Stratigraphy Commission of the Geological Society of London recommends formal adoption of international standard spellings for geochronologic and chronostratigraphic units of the rank Eonothem, Erathem, System, Series and Stage and their geochronologic equivalents as used by the International Commission on Stratigraphy. We recommend that these spellings should become standard in Geological Society publications and that the policy is advertised to the wider UK geological community."

(Incidentally, just in case the wording raises anyone's hackles more than is inevitable, the GSL considers both "stratigraphic" and "stratigraphical" as acceptable British English!)

The result was: for, 11; against, 6; abstain, 3; no replies, 4. The motion was carried. In this way it was agreed that issuing a British English version of the Chronostratigraphic chart was not desirable. It should be emphasized that the motion is not about wholesale adoption of American spellings of words such as "paleosol" and "paleontology" because it applies only to formally defined international stratigraphic terms of the five canonical ranks on the International Chronostratigraphic Chart. Hence part of the price to pay is that we will have to suffer combinations such as "Paleozoic palaeontology" when rendered in British English.

This motion was then passed to the GSL's Science Committee where, after further consultation with BGS, it was also approved and forwarded to Council, the ruling executive of the GSL, for consideration. Council also approved the motion and instructed the publishing house accordingly. It is important to point out that the GSL does not have the formal power to decide such matters for the UK – nobody does, not even the OED, which is specifically intended to reflect usage rather than laying down the law. It is up to the wider community – other learned societies, educational institutions, examining bodies, editors and individuals to decide whether or not to follow suit. We hope they will.


  • Berggren, W.A. 1998. The Cenozoic era: Lyellian (chrono)stratigraphy and nomenclatural reform at the millennium. In Blundell, D.J. and Scott, A.C. (eds), Lyell: the Past if the Key to the Present. Geological Society, London, Special Publications, v.143, p.111-132
  • Cohen, K.M., Finnet, S.C., Gibbard, P.L., and Fang, J.-X. 2013. The ICS International Chronostratigraphic Chart. Episodes, v. 36, p. 199-204.
  • Fowler, H.W. 1926. A Dictionary of Modern English Usage. Clarendon Press, Oxford.
  • Galvin, C. 1993. Review of Volume III, first edition, of Lyell's Principles facsimile edition from University of Chicago Press. Earth Sciences History, v. 12, p. 70-73.
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