Du Toit, Alexander Logie

(b. Rondebosch, near Cape Town, South Africa, 14 March 1878; d. Cape Town, 25 February 1948)

geology.

Du Toit was not only the most honored of South African geologists but also, in the words of R. A. Daly, the “world’s greatest field geologist.” To a remarkable degree he combined two traits not often found together: an extremely careful observer, he noted and drew deductions from details that escaped others, and at the same time he was able to synthesize information in broad fashion. Toward the end of his life he supported the hypothesis of continental drift with arguments drawn from all parts of the world and considerations about the underlying mantle.

Du Toit’s versatility of mind is demonstrated by the important contributions he made to such varied subjects as the stratigraphy of both Precambrian and Karroo beds, paleobotany, petrology, hydrogeology, geomorphology, and the economic geology of base metal, nonmetallic, and diamond deposits. He was very active and mapped the geology of more than 100,000 square miles, much of it in detail, using a plane table with a bicycle for transport and a donkey cart as a base.

Those who remember du Toit have a deep respect for his intellect, knowledge, and activity but an even greater regard for his modesty, frugality, and kindness to all. These qualities, coupled with a strong character, made him an outstanding leader of men and a dominant figure in any company.

Du Toit was born on his family’s estate near Cape Town. His father’s family, one of the largest and most distinguished in South Africa, was of Huguenot descent and had been in the Cape since 1687. His mother was Anna Logie, daughter of a Scottish immigrant. He went to school at the local diocesan college and graduated from South Africa College (now the University of Cape Town) before spending two years qualifying in mining engineering at Royal Technical College, Glasgow, and studying geology at the Royal College of Science, London.

While in Glasgow, du Toit married Adelaide Walker. They had one child, Alexander Robert. Du Toit’s wife died in 1923, and two years later he married Evelyn Harvey. At this period of his life he became a proficient musician, his favorite instrument being the oboe, and did some motorcycle racing.

In 1901 du Toit became lecturer at both the Royal Technical College, Glasgow, and the University of Glasgow. In 1903 he returned to South Africa to join the Geological Commission of the Cape of Good Hope. He spent the next seventeen years almost continuously in the field, mapping, at times accompanied by his wife and child. This period laid the foundations for his broad understanding and unrivaled knowledge of the details of South African geology.

His first season, spent with A. W. Rogers in the western Karroo, determined many of what were to become du Toit’s abiding interests. Together they established the stratigraphy of the Lower and Middle Karroo system noting the glacial origin of the Dwyka tillite. They recorded systematic phase changes from place to place in the Karroo and Cape systems. They mapped numerous dolerite intrusives, their acid phases, and their metamorphic aureoles.

From 1903 to 1905 du Toit was in the rugged Stormberg area, mapping so well that his accounts of the paleobotany of the coal-bearing Molteno beds and of the volcanicity have remained classics. From 1905 to 1910 he worked in the northern part of the old Cape Colony, mapping nonfossiliferous rocks of early Precambrian to Permian age. He became interested in geomorphology and hydrogeology and collaborated with Rogers in a new edition of the book Introduction to the Geology of Cape Colony.

Between 1910 and 1913 du Toit was near the Indian Ocean, mapping Karroo coal deposits, the flexure of the Lebombo Range along the coast, and an immense number of basic intrusions and charnockite rocks that he discovered there. In 1910 he received the D.Sc. degree from the University of Glasgow for his report on the copper-nickel deposits of the Insiza Range. His “Underground Water in South-East Bechuanaland” (1906) and “The Geology of Underground Water Supply” (1913) were important monographs which served to establish him as the leading authority on groundwater in South Africa. In 1914 du Toit visited Australia to study the rocks equivalent to the Karroo System and the groundwater geology of the Great Artesian Basin. From the outbreak of World War I until the campaign in South West Africa was over in 1915, he was hydrogeologist to the South African forces, holding the rank of captain.

Returning to Natal, du Toit became increasingly involved in work for the irrigation department and transferred to it in 1920. The relief from continuous fieldwork that this provided enabled him to produce a series of important papers and books on the Karroo System (1918), Karroo dolerites (1920), Carboniferous glaciation (1921), past land connections with other continents (1921), the South African coastline (1922), and the geology of South Africa (1926).

In 1923 a grant-in-aid from the Carnegie Institution of Washington enabled du Toit to make a trip to South America for the purpose of comparing the geology of that continent with that of Africa. He left Cape Town on 12 June and spent five months in Brazil, Paraguay, and Argentina. He described this visit in A Geological Comparison of South America with South Africa (1927), in which he also outlined points of similarity between the two continents.

He found the two continents to be alike in (1) Precambrian crystalline basement with infolded pre-Devonian sediments; (2) in the far north, a gentle syncline of marine Silurian and Devonian strata; (3) farther south, gently dipping Proterozoic and Lower Paleozoic strata cut by granites; (4) an area of flat-lying Devonian strata; (5) in the extreme south, conformable Devonian to Permian strata including Carboniferous tillites crumpled by later mountain building; (6) tillites extending northward transgressing across the Devonian on to the Precambrian basement before dying out; (7) glacial deposits overlain by continental Permian and Triassic strata with Glossopteris flora, followed by extensive basalt flows and dolerite intrusives; (8) Gondwana beds extending northward continuously from the southern Karroo to the Kaokoveld in Africa and from Uruguay to Minas Geraes in South America, with further great detached areas in the north, in each instance some distance inland, in the Angola-Congo and Piauhy-Maranhão regions; (9) an intraformational break occurring commonly below the late Triassic; (10) tilted Cretaceous beds occurring only along the coast; (11) widespread horizontal Cretaceous and Tertiary strata; (12) a succession in the Falkland Islands closely resembling that of the Cape, but distinct from that of Patagonia; (13) seven corresponding faunal assemblages in the similar strata; and (14) the geographical outline of the continent.

From 1927 to 1941 du Toit was consulting geologist to De Beers Consolidated Mines but continued to write on many topics; in 1937 he published his well-known book Our Wandering Continents. In 1932 he visited North America, in 1937 the Soviet Union, and in 1938 India. From his retirement until his death he lived at Cape Town and maintained his varied interests, extending them to include archaeology and vertebrate zoology.

Du Toit received many honors and awards, including five honorary degrees. He was twice president of the Geological Society of South Africa, a corresponding member of the Geological Society of America, and a fellow of the Royal Society of London.

More than most scientists, du Toit’s reputation, already high, has continued to grow, because in many of his deductions he was ahead of his time. His forte was meticulous and extensive fieldwork which enabled him to grasp virtually all aspects of the geology of South Africa. Many of the ideas that he espoused concerning groundwater, economic deposits of copper and nickel, and geomorphology and stratigraphy of rocks were original but not remarkably different from those held by others. The most significant factor of du Toit’s work was his early espousal of the theory of continental drift; he was the first to realize that the southern continents had at one time formed the supercontinent of Gondwanaland, which was distinct from the northern supercontinent of Laurasia. His championship of continental drift, unpopular at the time, is now widely hailed as having been correct.

BIBLIOGRAPHY

I.Original Works. Du Toit’s works include “The Stormberg Formation in Cape Colony,” in Report and Papers, South African Association for the Advancement of Science, 2 (1905), 47; “Underground Water in South-East Bechuanaland,” in Transactions of the South African Philosophical Society, 16 (1906), 251–262; “Report on the Copper-Nickel Deposits of the Insizwa, Mount Ayliff, East Griqualand,” in Annual Report of the Geological Commission for the Cape of Good Hope for 1910 (1911), pp. 69–110; “The Geology of Underground Water Supply,” in Mining Proceedings of the South African Society of Civil Engineers for 1913 (1913), pp. 7–31; “The Problem of the Great Australian Artesian Basin,” in Journal and Proceedings of the Royal Society of New South Wales, 51 (1917), 135–208; “The Zones of the Karroo System and Their Distribution,” in Proceedings of the Geological Society of South Africa, 21 (1918), 17–36; “The Karroo Dolerites of South Africa: A Study in Hypabyssal Injection,” in Transactions of the Geological Society of South Africa, 23 (1920), 1–42; “The Carboniferous Glaciation of South Africa,” ibid., 24 (1921), 188–227; “Land Connections Between the Other Continents and South Africa in the Past,” in South African Journal of Science, 18 (1921), 120–140; “The Evolution of the South African Coastline,” in South African Geographical Journal, 5 (Dec. 1922), 5–12; The Geology of South Africa (Edinburgh, 1926); A Geological Comparison of South America with South Africa, Carnegie Institution Publication no. 381 (Washington, D. C, 1927); Our Wandering Continents: An Hypothesis of Continental Drifting (Edinburgh, 1937); “Tertiary Mammals and Continental Drift,” in American Journal of Science. 242 (1944), 145–163; and “Palaeolithic Environments in Kenya and the Union—A Contrast,” in South African Archeological Bulletin, 2 (1947), 28–40.

II. Secondary Literature. On du Toit and his work see T. W. Gevers, “The Life and Work of Dr. Alexander L. du Toit,” Alexander L. du Toit Memorial Lecture no. 1, in Proceedings of the Geological Society of South Africa, 52 (1949), annexure 1–109; S. H. Haughton, “Alexander Logie du Toit, 1878–1948,” in Biographical Memoirs of Fellows of the Royal Society, 6 (1948), 385–395; and “Memorial to Alexander Logie du Toit,” in Proceedings. Geological Society of America, Annual Report for 1949 (1950), pp. 141–149.

J. T. Wilson