Biographical Memoirs: Digby Johns McLaren

11 DECEMBER 1919 * 8 DECEMBER 2004 DIGBY JOHNS McLAREN was born 11 December 1919 in Carrickfergus, County Antrim, Northern Ireland, and died 8 December 2004 in Ottawa, Ontario, Canada. He was predeceased in 2003 by his wife of sixty-one years, Phyllis Mary (Matkin), and is survived by their sons, Ian and Patrick, and their daughter, Alandra. Digby McLaren was a brilliant scientist and a visionary and inspiring leader within the Geological Survey of Canada, the Royal Society of Canada, and the Canadian, North American, and global geoscience communities. Digby attended St. Mary's School, Roxburghshire, Scotland, and Sedbergh School, Yorkshire, England, before entering Queen's College, Cambridge University, where he received a B.A. Natural Sciences, Part I, Geology, Mineralogy, Chemistry, in 1940. During World War II he served from 1940 to 1946 in the British army, Royal Artillery. For three and a half years he experienced the human misery and horrors of war as an artillery officer in the Middle East and in Italy, where he participated in the battle for Ortona. His first scientific paper, published in 1946 (in Italian), was on local geology in the Italian province of Perugia. In 1948 he received an M.A. Natural Sciences, Part II (First Class Honours), Geology, Paleontology, from Cambridge University. That year he joined the Paleontology section of the Geological Survey of Canada (GSC) in Ottawa, and began his studies of the Devonian rocks of western Canada. Digby McLaren was a remarkably gifted individual who had the good fortune to be in the right place at the right time. He arrived in Canada shortly after the unexpected 1947 discovery of a giant oil field in Upper Devonian (375-385 million years old) stromatoporoid-coral reefs at Leduc, near Edmonton, Alberta, an event that launched the amazing growth of Canada's oil and gas industry and sparked intense interest in the Devonian stratigraphy of western Canada. His initial research assignment in the GSC was to do the He began by studying the superbly exposed Upper Devonian strata in the nearby Rocky Mountains that are laterally equivalent to the Leduc reefs. Digby quickly mastered the intricacies of Upper Devonian regional and local reef-margin stratigraphy and the taxonomy of the Upper Devonian fossil brachiopods and corals that helped to elucidate many important aspects of the nature, origin, and evolution of the petroleum resource system. With encouragement and support from the GSC, he was able to fulfill the requirements for a Ph.D. in geology and paleontology at the University of Michigan by 1951. The scope of Digby's scientific experience expanded rapidly with his participation, in 1955, in Operation Franklin, a GSC aircraft-supported reconnaissance study of an immense area in Canada's western Arctic archipelago, and, in 1957, in Operation Mackenzie, a GSC helicopter-supported geological regional mapping project in the Mackenzie Mountains of the Northwest Territories. His research interests became focused on regional and global stratigraphic correlations and, in particular, on one of the global mysteries in the evolution of life on Earth-an abrupt mass extinction that occurred about 375 million years ago, between the Frasnian and Fammenian stages of the Upper Devonian. This extraordinary global event, marked by the abrupt disappearance of many species and families of organisms, including the obliteration of the Frasnian reef ecosystem that was responsible for the generation and entrapment of the petroleum at Leduc, was recognizable around the world. In his 1969 presidential address to the Paleontological Society, Digby's analysis of the available evidence led him to the conclusion that the most likely cause was an impact with a giant meteorite that disrupted the normal functioning of Earth's atmosphere, oceans, and biosphere. This bold hypothesis was controversial; it challenged prevailing ideas that favoured stable, gradual, non-catastrophic evolution of the Earth system. …

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