PRUVOST, PIERRE EUGèNE MARIE JOSEPH

(b. Raismes [Nord], France, 1 August 1890; d. Paris, France, 5 June 1967)

geology.

Though his father, grandfather, and brother were doctors, Pruvost studied the geological sciences. At nineteen he became an assistant at the Coal Museum of the University of Lille, directed by Charles Barrois. In 1918, at the University of Lille, he defended his doctoral thesis on the continental fauna of the coal-bearing regions of northern France; it was published the following year in the collection of explanatory treatises accompanying the geological map of France.

Pruvost was named lecturer in 1919 and professor of applied geology in 1922. In 1926 he succeeded his mentor, Barrois, in the chair of geology and mineralogy at the University of Lille, a position he held for twenty-four years. From 1943 to 1950 he was dean of the Faculty of Sciences.

In 1950 Pruvost accepted the chair of general geology at the Sorbonne, in which capacity he continued his research despite his heavy administrative and teaching assignments. He devoted much of his time to the young geologists whose work he guided.

Highly esteemed in university, scientific, and industrial circles, Pruvost was twice elected president of the Geological Society of France (1948, 1963) and presided over many scientific and university institutions, such as the National Geology Committee and the geology sections of the National Council of Scientific Research and the Universities Consultative Committee. He was elected corresponding member of the Academy of Sciences in 1947 and full member in 1954. He was also a corresponding foreign member of the Academy of Sciences of Lisbon and the Royal Academy of Belgium.

Pruvost’s achievements were recognized in many awards: officer of the Legion of Honor (1949), commander of the Ordre des Palmes Académiques (1959), commander of the National Order of Merit (1966), and officer of the Crown of Belgium (1948). He was an honorary member of the geological societies of Belgium, England, Scotland, Sweden, Switzerland, and the United States, and received honorary doctorates from the universities of Louvain and Mainz. He was awarded the Prix Gosselet and Prix Gaudry of the Geological Society of France, the Prix Kuhlmann of the Lille Society of Sciences, and several medals from various European geological societies.

These honors never affected Pruvost’s modesty; upon his election to the Academy of Sciences, he established a prize meant to encourage young researchers, the Pierre Pruvost Foundation Prize, awarded annually by the Geological Society of France.

Pruvost’s scientific work was enormous, as evidenced by his more than 200 articles dealing with the stratigraphy of the Paleozoic, the paleontology of coal, the geology of coal basins, the relation between tectonics and sedimentation, and the geology of the Armorican Massif.

Pruvost did considerable research in the coal basins of western Europe, including those of Nord and the Pas de Calais, the Saar-Lorraine Basin, the Belgian Basin, and the St. Étienne Basin. He made a great contribution to the stratigraphy of the Upper Paleozoic, emphasizing the importance of the break between the Autunian and the Saxonian, which he related to the Saalian phase. (In Europe this coincided with the initial raising of the Urals, leading to the formation of the Eurasian bloc.) With W. J. Jong–mans, Pruvost proposed to incorporate the Autunian into the Carboniferous and to adopt the term “Pennsylvanian” to define the totality of terrains ranging from the Namurian to the Autunian.

Discussing the Precambrian-Paleozoic boundary, Pruvost proposed to incorporate into the Paleozoic a sedimentary layer noted in the Anti-Atlas Mountains of Africa and in North America that, conformably distributed under the olenellus biozone of the Lower Cambrian, is strongly discordant with the Precambrian. This stratum, known as Infracambrian, a term used by Nikolai Menchikov, corresponds to a period of 130 million years. Although the term has been abandoned, the discussion that lay at its origin remains an excellent example of stratigraphic reasoning.

Pruvost’s earliest work was devoted to the description of the rich and varied fauna of the coal-bearing regions of the Nord and Pas de Calais basins. He then undertook a monograph on the continental fauna of the Belgian coal-bearing region, which he compared with that of other European basins. This enabled him to forge a synthesis of the chronology of the continental fauna of the coal regions of western Europe, which was presented at international congresses held in Brussels (1922) and Heerlen (1927).

On the basis of work conducted in the coal basins of western Europe, Pruvost developed several ideas that proved fundamental in paleographic reconstruction. He conceived the notion of lateral variation of facies: The outer reaches of coal basins are marked by deposits of large detrital rock and conglomerated accumulations of vegetal debris that produce coal, as well as claylike mud formed of the remains of fish, which sometimes becomes oil shale. Veins of coal are therefore deposited in annular form, concentrically around the banks of the original basin. Pruvost also recognized that the zone of alluviation of a basin may be displaced by the rising of edges such that the sedimentary series is rarely complete along any given vertical. Yet another of his contributions was the idea of subsidence, defined as a “prolonged and continuous descending movement produced by repeated drops of slight amplitude in a submerged region of the earth’s crust in which an appreciable thickness of sediments is accumulated by virtue of this phenomenon. “This concept explains the rhythmic alternation of veins of coal and sterile rock several thousand meters thick in terrains whose nature suggests deposits of slight depth.

Pruvost’s Armorican activity dates back to 1924, when, at the invitation of Barrois, he contributed to revising the geological map of Redon. He continued to be interested in this region, in which he conducted many geological investigations. In “Lesmers et les terres de Bretagne aux temps paléozoïques” (1949) he presented a paleographic sketch of the Armorican Massif for the Paleozoic era. This sketch indicated the existence of a central east-west pit marked by the Chateaulin-Laval synclinorium median, the site of nearly continuous sedimentation during the Paleozoic, a pit bounded by two mountain ranges, Domnonée in the north and Ligeria in the south. This schema is still employed in paleographic reconstitutions of the Armorican Massif.

Pruvost was a man of great culture, gifted with a lively intelligence and devoted to his work. He was also sensitive and attentive, and his willingness to help others was legendary. Many young scientists found welcome refuge in his Sorbonne office, where his kindness put them at ease despite the solemnity of the surroundings. An opponent of dogmatism of any kind, Pruvost sought to awaken the intelligence of the young through an objective and rigorous approach, often suggesting several interpretations where it would have been easier to propose just one. He rejected the notion of schools of thought as excessively constraining. He was always careful of people’s feelings, and considered his collaborators friends rather than colleagues. Pruvost was concerned that all people have the chance to be themselves, for he held that the richness of thought rests on the diversity of human nature.

BIBLIOGRAPHY

I. Original Works. “Introduction à l’étude du bassin houiller du Nord et du Pas-de-Calais: La faune continentale du terrain houiller du nord de la France”, in Mémoires pour servir à l’explication de la Carte géologique détaillée de la France (Paris, 1918): “Les divisions paléontologiques dans le terrain houiller de l’Europe occidentale, d’aprés les caractères de la faune limnique”, in Congrès géologique internationale, Bruxelles. Comptes-rendus de la XIII^esession, II (Brussels, 1922), 639–654; “La faune continentale et la division stratigraphique des terrains houillers (Europe occidentale)”, in Comptes-rendus du Congrés internationale de stratigraphie et de gèologie du carbonifere (Heerlen, 1927), 519–534; “Sédimentation et subsidence”, in Livre jubilaire de la Société géologique de France. . ., II (1930), 545–564; “Introduction à la faune continentale du terrain houiller de Belgique”, in Mémoires du Musée royal d’histoire naturelle de Bruxelles, no. 44 (1931); “Un bassin houiller paralique de l’époque crétacée”, in Comptes-rendus hebdomadaires des séances de l’Académic des sciences, 214 (1942), 847–848; “Les mers et les terres de Bretagne aux temps paléozoiques”, in Annales Hébert et Haug, 7 (Livre jubilaire Charles Jacob) (1949), 345–362; “Les subdivisions du Carbonifére continentale”, in Bulletin de la Société géologique de France, 5th ser., 20 (1950), 335–344, with W. J. Jongmans; and “L’Infracambrien”, in Bulletin de la Société belge de géologie, de paléontologie et d’hydrologie, 60 (1951), 43–65.

II. Secondary Literature. John R. Fanshawe, “Memorial to Pierre Pruvost (1890–1967),” in Proceedings, Geological Society of America, 1967 (1970), 243–251, with bibliography and a portrait; Jean Piveteau, “Notice nécrologique sur Pierre Pruvost (1890–1967), membre de la section de minérologie et géologie”, in Comptes-rendus hebdomadaires des séances de l’Académie des sciences, 266 (1968), 110–114; P. Routhier and G. Waterlot, “Pierre Pruvost (1890–1967)”, in Bulletin de la Société géologique de France, 7th ser., 10 (1968), 519–534, with a bibliography of 207 references and a portrait; and Titres et travaux scientifiques de M. Pierre Pruvost (Paris, 1954), with a bibliography of 168 references.

Michel Colchen