(b. La Hulpe, Belgium, 25 December 1877; d. Liège, Belgium, 20 January 1970)
In 1895 Fourmarier enrolled in the mining engineering course at Brussels University and then at Liège University, where he studied with Max Lohest. He received a degree in mining engineering in 1899 and in geological engineering in 1901, both from Liège.
Soon after graduation Fourmarier joined the Bureau of Mines as a mine inspector, thereby gaining firsthand knowledge of the tectonic structures of coalfields. At the same time he was appointed a teaching assistant at Liège University, where he showed a talent for teaching, and was before being invited to join the Geological Commission, where hr worked on the revision of André Dumont’s geological map. Fourmarier was responsible for revising the HamoirFerrières, Seraing and Chenèe map sheets of the Ardennes.
In 1901 Fourmarier published a revised geological map of the Theux region, where a Devonian-Carboniferous basin, surrounded on three sides by a curved fault, was supposedly sunk into Lower Devonian rocks. However, a new excavation for a second railroad track between Pépinster and Theux exposed the superposition of Lower Devonian upon Carboniferous beds. This Theux fault was obviously a thrust, but it dipped to the north. Having carefully described the new exposure, Fourmarier was puzzled by this thrust apparently opposite to the usual direction. If the displacement was northward, as elsewhere, could this be an underthrust? But it would have to be an odd kind of underthrust, engulfing the Carboniferous on three sides, under the Lower Devonian.
This idea illustrates the uncertainty that still existed, even among the best workers in tectonics, Henri de Dorlodot concurred, after having conceived and rejected the interpretation that was later shown to be correct: that the Theux fault forms the frontal northern limit of a tectonic window (the concept had hardly been defined, and no term had yet been proposed for it). Dorlodot used the term “eyelet”(oeillet in French) to describe this still hypothetical structure. But, relying on field evidence, he rejected his hypothesis because of the very meager evidence regarding the Marteau fault, which should have closed the window to the southeast. This is indeed a weak point. The southeastern closure of the Theux circular fault was to remain a problem until 1950, when Fernand Geukens traced it further south, well into the monotonous pre-Devonian basement.
That the medieval town of Theux lies in the middle of a tectonic window was established by Fourmarier’s research in 1905. The demonstrative criterion emerged from a detailed study of the facies variations in the Devonian limestones within the window and along the Ourthe Valley, in the nappe. As confirmed by a revision by Marie Coen-Aubert in 1974, this tracing of isofacies lines demonstrates a 12-kilometer (7.5-mile) horizontal displacement of the nappe northward with regard to the window.
If this hypothesis was correct, the Carboniferous should underlie the Lower Devonian, and a new coalfield might be discovered. Accordingly, two test boreholes were drilled near Pépinster, north of the window. They reached the coal measures—unfortunately barren—underneath the Lower Devonian of the nappe. This added the final point to the demonstration.
Fourmarier’s detailed mapping also had disclosed two smaller windows within the larger window at Oneux. More complex than might have been thought at first, the Theux window, one of the first and best-documented examples of a tectonic window, thus acquired wide renown.
On a regional scale, the tectonic structure of the Ardenne is somewhat symmetrical. In the east it must be related to the Midi overthrust, which extends east toward Aachen. In the west the La Tombe klippe relates to the Midi overthrust, which has been traced westward, south of the concealed coalfields of northern France, to the Boulonnais inlier on the Channel coast. Between these two thrust segments, the intermediate “Condroz” segment was interpreted by Dorlodot as a major overfold. Fourmarier advocated that this structure be replaced by a charriage du Condroz connecting the western and eastern thrusts. This major overthrust, the frontal structure of the Hercynian chain in Western Europe, is well documented by seismic prospection and confirmed by several deep boreholes.
This synthesis brings to the fore the two kinds of tectonics proposed by Pierre Termier. Albrecht Heim had drawn tectonic nappes in the Alps in the form of recumbent anticlines with stretched inverted limbs, an image that Marcel Bertrand had employed in Provence and that, after acceptance of Maurice Lugeon’s Alpine synthesis, was taken by Termier as the general model of nappe structure. This model has since gained a wide, if rather undue, acceptance. It had inspired Dorlodot to put forth his recumbent Condroz anticline; nevertheless, he and (now) Fourmarier offered as evidence against this “stretching” style the clear-cut shearing across the limbs of the folds, as seen both in outcrop and underground in the mine profiles. With Fourmarier’s tectonic synthesis the Ardennes thus became the type locality of Termier’s tectonic “second genre.” The 1922 meeting of the International Geological Congress in Belgium provided the opportunity for demonstrating these structures in the field.
In fact, the Assynt slices (northwestern Scotland), the Appalachian thrust sheets, those of the northern Rockies, the Katanga (now Shaba) thrust belt, and many others all exhibit this shearing style. Even the Helvetic Alps, where the Morcles overfold remains an exception, belong to this “second genre,” which thus represents the prime type of overthrusting. Fourmarier’s analyses and syntheses of 1907, 1934, and 1954 exemplify the tangential style of tectonics, except perhaps for his overemphasis of the idea that thrusting develops only after folding instead of the contrary, as is generally accepted today.
In 1919, he was elected to the Royal Academy of Belgium, over whose committees for geology and geography he later presided. In 1920. Fourmarier was appointed professor of mining geology, hydrogeology, and mining and industrial geography, and in 1927 professor of physical geology, at Liège University. As was usual in Belgium, he linked geomorphology to geology. An enthusiastic teacher and superb speaker, for almost three decades he taught many young geologists, mining engineers, and geographers, He wrote textbooks on physical geology and hydrogeology, and also edited the Prodrome, on the regional geology of Belgium.
In 1913, on a mission to central Africa, Fourmarier traveled, mostly on foot, through bush and forest to the shores of Lake Tanganyika. There he mapped the Lukuga coalfield (now in Zaïre) and explored the Malagarassi Valley (now in Tanzania).
Having become acquainted with the intricate correlation of the mostly nonfossiliferous formations of central Africa, Fourmarier proposed a synthesis of the sometimes divergent proposals by drawing, in 1924, the first geological map of the Congo Basin, on the scale of 1:4, 000, 000; it was revised and amplified in 1930 on the scale of 1:2, 000, 000. The success of this work brought him the further task of organizing, in 1929, the Geological Commission (within the Colonial Office), which he headed for thirty years. He was coauthor of the International Geological Map of Africa, and honorary president of the Association of African Geological Surveys. He was also one of the founding members, in 1929, of the Royal Colonial Institute, which later became the Royal Overseas Academy of Sciences.
In the realm of theory, Fourmarier considered the megatectonic pattern of crustal architecture on a planetary scale. Ideas about the symmetry and permanence of continents and oceans, and the parallelism of folded belts tightly wrapped around the pre-Cambrian shields, underlie the three fundamental rules that he proposed to explain the evolution of the earth’s crust. This was an advance on the ideas of Eduard Suess, Émile Haug, and Hans Stille, but Fourmarier was nevertheless strongly opposed, as were most geologists of the period, to the then misunderstood intuitions of Alfred Wegener.
These speculative endeavors did not prevent Fourmarier from returning frequently to the field. Short of build and seemingly frail, he was nevertheless an energetic and tireless walker. Throughout his teaching career, and long after his retirement in 1948, he continued to revise attentively the structures of the Paleozoics south and east of Liège, mapping in detail the fault traces, appraising their importance, and evaluating the possible role of cross faults.
His wide travels through many continents had brought him in touch with a variety of geological settings where his keen eye promptly recognized the structural pattern. This explains why among his many interests he took the trouble to bring together field observations concerning minor structural types such as slaty cleavage from far and wide. He pursued this endeavor with mixed success—he was not a microscopist—but with unabated enthusiasm until the very last years of his life.
Faithful to his motto “He who devotes heart and soul to scientific pursuits will keep working up to the threshold of the grave,” he published six papers in 1969 and, despite his failing eyesight, left on his desk an unfinished manuscript when he died in January 1970at the age of 92.
He was an inspiration to many younger geologists. Colleagues from all over the world heaped fame and honors upon him. An associate of the Institut de France, of the Spanish Academy at Madrid, and of many other academies and institutions, he received the Wollaston, Penrose, Gaudry, and van Watershoot van der Gracht medals and was awarded honorary doctorates by the universities of Paris, Lille, Grenoble, Caen, and Geneva. However, it is likely that he took greater pride in the British War Medal and the Médaille de la Résistance, awarded for his actions during World War I and World War II, respectively.
1. Original Works. Only a few works by Fourmarier can be mentioned here; most were published in Annales de la Société géologique de Belgique (ASGB). Bulletin or Mémoires de la classe des sciences de l’Académie royale de Belgique (BARB or MARB), or Proceedings of several International Geological Congresses.
On the Theux window, see “Le bassin dévonien et carboniférien de Theux,” in ASGB, 28 (1901), 27–53;” La structure du massif de Theux,” ibid., 33 (1906), M109–139; and the map sheet Louveigné-Spa (with “Notice explicative’) of Carte géologique de la Belgique à l” échelle du 25.000-ème (Brussels, 1958).
The Ardennes tectonic synthesis was first proposed in “La tectonique de l’ Ardenne,” in ASGB, 34 (1907), M15123, and restated in “Vue d’ ensemble sur la géologie de la Belgique,” ibid., in Mémoires, 8 (1933–1934), and in the chapter on tectonics in the Prodrome (see below). See also the 13th IGC Guidebooks A1, B2, and C2 (1922); and planche 10—tectonique (with “Commentaire”), in Atlas national de Belgique (Brussels, 1953).
His Principes de géologie went through three editions (Paris, 1933; 2nd ed., 1944; 3rd ed., 2 vols., 1949–1950). His textbook Hydrogéologie: Introduction à l’ étude des eaux destinées à l’alimentation humaine et à l’industrie went through two editions (Paris, 1939; 2nd., 1958). Prodrome d’une description géologique de la Belgique (Liège, 1954) remains the best source on the geology of Belgium.
A bibliography of his works on Africa is given in full in Denaeyer’s obituary notice (see below). His geological map of the Belgian Congo was published in Revue universelle des mines, 7th ser., 4 , no.4 (15 November 1924).
On the three fundamental rules of crustal evolution, see “Les is idées actuelles sur les déformations de l’écorce terrestre et la dérive des continents,” in Revue universelle des mines, 7th ser., 18 (1928), 39; “Essai sur la probabilité de l’existence d’une règle de symétrie dans l’architecture de I’ écorce terrestre,” in MARB, 2nd ser., II, fasc. 2 (1930), 3–46; “Recherches sur I’ existence d’une règle de symétrie…” in World Engineering Congress, Tokyo (1929); Trois regles fondamentales de I’architecture de I’ecorce terrestre (Paris, 1932); “Recherches Complémentaires sur I’existence d” une regle de symetrie… “in proceedings of the Sixteenth Iternational Geological Congress (1935).925–936;” La derive des continents et la regle de symetrie” in BARB, 5 th ser. 22 (1938), 1391–1414; “La regle de symetrie appliquee á la geomorphologie,” in Bulletin de la Sicuete belge d etudes geographiques, 8 (1938), 20–40;” Efforts tangentiels et efforts verticaux dans la tectonique, ’in ASGB, 49 (1946), B88182;” Le probleme de I’origine des continents, ’in BARB, 5th ser., 48 (1961), 1368–1426; “L arrangement systematique des continents et des oceans.” in Melanges de geographie physique, humaine, economique, appliquees offerts a M. Omer Tulippe (Gembloux.1967) 5–25; “Le probleme de la derive des continents.” in MARB, 2 nd ser., 17 , no. 2 (1969).
Papers relating to slaty cleavage include “Le clivage schisteux dans les terrains paléozoiques de la Belgique,” in Proceedings of the Thirteenth International Geological Congress (1923). 517–530;” De I importance de la charge dans le développement du clivage schisteux.” in BARB. 5th ser. 9 1923).454–458;’Observations sur le developpement de la schistosite dans les series plissees, :in BARB 5th ser., 18 (1932), 1048–1053;’Schistosite. foliation et microplissement, ’in Archives des sciences (Geneva), 4 (1951), 5–23;’Schistosité et grande tectonique,” in ASGB, 76 (1953), B275–301; “Le granite et les deformations mineures des roches, ’in MARB, 31 (1959), 3–101;” Les deformations mineures des roches.…’in Memoire FALLOT, Societe geologique de France (1961), 57–81;’L interet de I etude des deformations mineures des roches….” in Revue des questions scientifiques, 26 (1965), 438–517; and “La montee systematique des fronts de schistosite en rapport avec la granitisation.” in MARB, 39 (1969).
II Secondary Literature. An obituary notice appeared in Annuaire de I” Academie royale de Belgique (Brussels) by Paul Michot, who has published a short obituary notice in ASGB, 93 (1970), 425–429. Notices also are in Bulletin de la Société géologique de France, 7th ser. 13 ( 1971)205–213, with an extensive bibliography, by Léon Calembert, and in Bulletin des séances de I’Académie des sciences d’Outremer à Bruxellers (1971) 7185, with a complete bibliography of works relating to Africa, by Marcel E. Denaeyer.
Pierre De BÉthune