Cayeux, Lucien

(b. Semousies, Nord, France, 26 March 1864; d. Mauves-sur-Loire, Loire-lnférieure, France, 1 November 1944),

sedimentary petrography, stratigraphy.

Cayeux’s youth was spent in the Avesnois, the country surrounding Semousies, where, after completing his secondary education, he taught for a short period at the primary school of Avesnes-sur-Helpe.

Désiré Piérart, an enthusiastic collector of fossils from the neighboring village of Dourlers, had a strong influence on the farmer Xavier Cayeux and his son Lucien. He awoke the son’s interest in geology and prompted the father to send him to Lille to study under Jules Gosselet and Charles Barrois. While working for his master’s degree, Cayeux was appointed their assistant, or more correctly their préparateur in 1887. This is a peculiar position in the French academic system that combines the preparation of materials for classroom and laboratory demonstrations with curatorial duties, participation in administrative work, and personal research. Such an assistant is supposed to spend equal time on professional services and on his own research, a combination that develops a strong interest in original investigations and a deep sense of academic duty, It was the ideal start for an energetic and industrious man like Cayeux.

In 1891 Marcel Bertrand offered Cayeux the position of préparateur at the National School of Mines in Paris. Tom for a while between Gosselet’s exhortation to stay at Lille and Barrois’s advice to take advantage of the vast scientific resources of the capital, Cayeux eventually went to Paris and never regretted his decision. While at the School of Mines he completed his doctoral dissertation and defended it in Lille in 1897. Appointed in 1898 to the National Agronomical Institute, Cayeux occupied several positions at that institution and in 1901 became professor of agricultural geology. His teaching in this new field of applied geology met with great success.

In 1904, when Marcel Bertrand had to resign from the School of Mines for reasons of health, Cayeux replaced him as assistant professor; and after Bertrand’s death in 1907 he became, contrary to a well-established tradition, professor-in-charge. Five years later he was called to the chair of geology of the Collège de France, to take the place of Auguste Michel-Lévy. In this final position of his career Cayeux spent twenty-four years developing the teaching of the petrography of sedimentary rocks, which closely reflected his personal research.

In 1936 new administrative regulations forced Cayeux’s retirement, depriving him of three years of teaching during which he was planning to complete his carefully organized academic program. This situation greatly embittered Cayeux, who then dedicated himself entirely to research in his own laboratory at the School of Mines. At the outbreak of the war in 1939 he secluded himself on his properly at Mauvessur-Loire, where in previous years he had spent long periods. During this last portion of his life Cayeux combined the delicate and demanding task of mayor of a town under German occupation with the completion of some of his scientific works. He wrote the synthesis of his long and unique experience, a remarkable booklet entitled Causes anciennes et causes actuelles en geologic, a subject he had planned to discuss during the last year of his teaching at the Collège de France.

Cayeux’s fundamental contribution pertains to the petrography of sedimentary rocks, a field of which he is considered one of the founders. His doctoral dissertation was the first of an impressive series of memoirs dealing with such rocks. It consists of a study of the chalk of the Paris basin and of certain siliceous rocks (gaizes, meules, tuffeaux) peculiar to the Mesozoic and Cenozoic formations of northern France and Belgium. When Cayeux began his investigation of the sedimentary rocks, they had been largely neglected in comparison with metamorphic and igneous rocks, on which rapid progress had been accomplished under the leadership of such scientists as Zirkel, F. Fouqué, Michel-Lévy, Rosenbusch, and Lacroix. Only H. C. Sorby and Sir John Murray in Great Britain had understood the potential importance of the petrogaphic study of the sedimentary rocks. In order to succeed in such a task, one had to be a petrographer, a paleontologist, a stratigrapher, and a chemist; Cayeux met all these prerequisites.

In his doctoral dissertation Cayeux outlined his superb analytical method of investigation and stated his aims, which were to remain the same in his later works. He first describes the components of a sedimentary rock: detrital minerals, authigenic or secondary minerals generated within the rock itself, organic remains, and cement or matrix holding these components together. Adding the results of chemical analyses to the spectrum of microscopic observation his synthesis attempts to determine the original characters of the sediment and the provenance of its detrial components. Finally, he follows through geological time the diagenetic modifications undergone by the sediment after its deposition.

For Cayeux the science of sedimentary rocks was essentially the complete natural history of ancient and recent sediments. It was therefore natural that he relied heavily upon the wealth of data collected by the Challenger expedition, using them for comparative purposes in order to understand the genesis of ancient sediments on the basis of recent ones. Hence he created a new approach: paleo-oceanography.

After his investigation of the chalk, in which he demonstrated that in spite of apparent analogies with the recent deep-sea Globigerina ooze, it was a shallow-water sediment. Cayeux undertook a series of comprehensive and well-illustrated monographs, concerned particularly with the sedimentary rocks of France and its colonies. He successively applied his unusual analytical gifts to the Tertiary sandstones of the Paris basin (1906), the Paleozoic and Mesozoic oolitic iron ores (1909, 1922), the siliceous rocks or cherts (1929), the phosphates (1939, 1941, 1950 [ post-humous]), and the carbonate rocks: limestones and dolomites (1935). Although Cayeux’s interpretation of the oolitic iron ores did not gain general acceptance, his synthetic views on the genesis of siliceous rocks, phosphates, and carbonates show an amazingly modern character. Particularly in carbonate rocks he anticipated a great number of modern trends concerning early diagenetic changes, such as induration, recrystallizaiion, and dolomitization.

As a result of his year of teaching at the Collè gede France, Cayeux produced his Introduction à l’é tude pétrographique des roches sédimentaires, published in 1916, out of print in 1927, and reprinted in 1931. In this beautifully illustrated monograph that obviously filled a need among geologists, he gave an exhaustive account of all the methods of analyzing sedimentary rocks: physical, microchemical, and chromatic. He then proceeded to distinguish all the constitutive elements of these deposits, describing each individual mineral species as well as the various organisms that contributed to their genesis. Of particular interest is a long chapter on the microstructure of the skeletal remains of living and fossil organisms. Sedimentary petrographers are still waiting for a modern equivalent of this masterpiece.

These outstanding monographs, usually preceded by the publication of numerous short papers—which total more than 270—should not, however, lead one to ignore another interesting aspect of Cayeux’s long career. Between 1900 and 1904 he served as geological adviser to the archaeologists working in Greece and in the archipelago, sponsored by the French School of Athens. In that capacity Cayeux undertook a detailed study of the island of Delos, determining, among other things, that the mean sea level on the shores of the eastern Mediterranean had not changed appreciably since remotest antiquity. He also undertook an interesting petrographic study of the building and decorative materials that the ancient Greeks used in construction and adornment of the famous temple of Apollo and the determination of their geographic and geological origin. Cayeux’s survey of Crete and of the Peloponnesus remained unachieved. He did, however, demonstrate the occurrence of overthrusts in the mountains of the southern part of the country.

Cayeux’s philosophical approach to geology underwent a remarkable evolution throughout his life. In his first work on the chalk of the Paris basin, he attributed a great importance to the time factor in diagenesis, assuming that the chalk would undergo, after deposition, many changes toward a stable condition, through a long span of geological time and under the action of the everlasting causes postulated by the concept of uniformitarianism. His subsequent studies on iron ores, cherts, phosphates, and carbonates gradually revealed to him that many fundamental features of these deposits had been generated contemporaneously or penecontemporaneously with deposition by submarine processes of reworking, transportation, induration, and recrystallization, and that such deposits underwent no other major changes after emergence. Furthermore, Cayeux stressed that most of these processes, so clearly expressed in ancient sediments, were not active in present-day oceans. Therefore, he concluded that serious consideration should be given to the dual concept of past and present causes in geology. This fundamental challenge to uniformitarianism ended Cayeux’s scientific contribution with an issue that remains to be resolved by geologists.

BIBLIOGRAPHY

I. Original Works. Cayeux’s writings include “Contribution à l’étude micrographique des terrains sédimen-taires, I. Étude de quelques dépôts siliceux, secondaires et tertiaires du bassin de Paris. II. Craie du bassin de Paris,” Méemoires de la Société géologique du Nord, 4 , no. 2 (1897) Structure et origine des grès du Tertiaire parisien, in the series Études des gítes minéraux de la France (Paris, 1906); Les minerals de fer oolithique de France. Fascicule I: Minerais de fer primaires, in the series Études des gítes miné rauxde la France (Paris, 1909); Description physique de l’íle de Délos, vol. IV of Exploration archéologique de Délos,.. (Paris, 1911); Introduction a l’étude pétrographique des roches sédimentaires, in the series Mémoires explicatifs de la Carte géologique détaillée de la France. 2 vols. (Paris, 1916; repr. 1931); Les minerals de fer oolithique de France, Fascicule II: Minerais de fer secondaires, in the series Études des gítes minéraux de la France, (Paris, 1922); Les roches sédimentaires de France. Roches siliceuses, in the series Mémoires explicatifs de la Carte géologique détaillée de la France (Paris, 1929); Les roches sédimentaires de France Roches carbonatées (calcaires et dolomies) (Paris, 1935) annotated English trans. by Albert V. Carozzi (New York, 1970); Les phosphates de chaux sédimentaires de France (France métropolitaine et d’outre-mer), I (Paris, 1939); Causes anciennes et causes actuelles en géologique (Paris, 1941), annotated English trans, by Albert V. Carozzi (New York, 1970); Les phosphates de chaux sédimentaires de France (France métropolitaine et d’outre-mer), II, É gypte, Tunisie, Algérie (Paris, 1941), pp. 351–659, pls. XVIXXXIII; and Les phosphates de chaux sédimentaires de France (France métropolitaine et d’outre-mer), III, Maroc et conclusions générales (Paris, 1950), pp. 661–970, pls. XXXIV-LIV.

II. Secondary Literature. For further information on Cayeux and his work, see L. Bertrand, “Notice sur l’oeuvre de Lucien Cayeux (1864–1944),” in Notices et discourse. Académie des sciences, II, 1937–1948 (Paris, 1949), 607– 632 M. Leriche, “La vie et l’oeuvre de Lucien Cayeux (1864–1944)” in Bulletin de la Société belge de géologie, 55B (1946), 259–314, with complete list of publications; and “Lucien Cayeux (1864–1944),” in Bulletin de la Sociéeté géologique de France, 5th ser”., 17 (1947), 349–377, with complete list of publications; and E. Margerie. “Memorial to Lucien Cayeux,” in Proceedings of the Geological Society of America for 1947 (1948). 131–133.

Albert V. Carozzi