Obituaries Australia

Ian McDougall, by Warren Hudson, 1988

ANU Archives, ANUA 579-514

An appreciation of a long journey in science.

Professor Ian McDougall, a distinguished geologist, died on 10 November at the age of 83. Ian came to ANU in 1957 and his entire scientific career was here: first in the Department of Geophysics in the Research School of Physical Sciences and then in the Research School of Earth Sciences (RSES) when that School divorced from RSPhysS.

In 1957 he had completed his undergraduate studies at the University of Tasmania where he was strongly influenced by (but not under the spell of) S. Warren Carrey, a legendary figure and influential proponent of drifting continents and an expanding earth. At ANU he was a student of Germaine (Joppy) Joplin in the Department of Geophysics and completed his PhD in 1960 with a thesis on the petrology and geochemistry of a magma intrusion in Tasmania (the Red Hill Intrusion, a tholeiitic magma that had intruded Permo-Triassic sediments)—seemingly a rather uninspiring topic, but one that prepared him exceedingly well in both field and laboratory for the career that was to follow.

Professor John Jaeger, another influential figure in the Earth Sciences, at that time was building up the ANU department by largely avoiding mainstream geology and geophysics and focusing on new experimental-based emerging fields. He had heard about the developments in geochronology and saw opportunities to develop this at ANU. (Interestingly, in going down this path, he was partly influenced by Professor Anton Hales at the Bernard Price Institute in South Africa and who was the founding Director of RSES.) One of these techniques was the potassium-argon isotopic dating method then under development at the University of California in Berkeley and he invited Jack Evernden, aided by John Richards from Radiochemistry in RSPhysS, to ANU to set up this facility. Ian was well prepared to accept this challenge as Jaeger arranged for Ian to spend a year at Berkeley to become familiar with the technique and to think about possible applications that could be developed back at ANU.

On his return to Canberra, now as a newly appointed Research Fellow, Ian arranged to sample the volcanic islands in the Hawaiian chain: the high islands from Kauai to the big island of Hawaii over a distance of ~530 km with the samples from the eastern end being from recently extinct volcanic centres. The objective of this sampling was to test the then recent hypothesis that these islands should show a progression of increasing age from the east to west. In Ian’s own words: ‘Most people at the time were very pessimistic about dating such young rocks’ and he had to push the K/Ar method to its limits. This turned out to be a remarkably successful experiment thanks to Ian’s careful experimental work and provided the exciting scientific result: that it proved the age progression of the volcanos and supported the Hotspot model of Tuzo Wilson (proposed in 1963) for the origin of volcanic island chains in which the Pacific lithosphere moved over more-or-less stationary mantle convection plumes. Subsequent work was carried out with his student Robert Duncan on other Pacific island chains, including the Society, Austral and Marquesas island chains. These gave concordant ages and directions of the migration of volcanism and led to the confirmation that these volcanoes recorded the motion of the Pacific Plate over the last ~100 million years

The Hawaiian K/Ar results were combined with palaeomagnetic studies undertaken concurrently by PhD student Don Tarling in ANU, yielding, among other things, evidence for the reversal of the magnetisation through time. It became apparent that there was a zonation of normal and reversed polarity with time, not only showing that reversed magnetisation was real, but that it was possible to determine a polarity time scale. With similar work at the US Geological Survey, the ANU work quickly made a very major contribution to the development of the geomagnetic time scale, a time scale that also was found applicable to the calibration of the age of magnetic ‘stripes’ on either side of mid-ocean ridges, and hence rates of seafloor spreading.

These two developments provided the corner stones upon which the subsequent plate tectonics hypothesis was built and accepted. The significance of both are well documented in F.R. Hankel’s The Continental Drift Controversy (Vol. 2: Paleomagnetism and confirmation of drift), and in Bill Menard’s book The Ocean of Truth.

The K/Ar method continued to be refined by Ian, including the development of 40Ar/39Ar isotopic dating method, single crystal dating and the introduction of computer-driven data acquisition and automation methods. This latter led to a significantly increased the throughput of his laboratory, with a generation of students trained under his guidance, and in the range of geological problems addressed of Australian and international significance. This was never at the expense of loss of quality and I doubt if ever one of his results has been seriously questioned.

An important shift in application occurred in 1978 when he became involved in the dating of the volcanics in northern Kenya, the cradle of hominin evolution, where he was able to resolve apparent inconsistencies in the ages of the oldest fossils. Using both the K/Ar and 40Ar/39Ar methods, he was able to place very accurate age-constraints on the volcanic tuff (the KBS Tuff, dated at 1.86 ± 0.02 Ma old) above what became the then oldest known hominin fossils. By combining his meticulous geological field skills with his equally careful laboratory work, he extended this work to Ethiopia and established the time scale for early human evolution in East Africa. The significance of this work is documented in, for example, William Glen’s book, The Road to Jaramillo. In a letter to Pam McDougall, Meave Leakey has written: ‘Without Ian’s input, we would have struggled to find meaning in the stratigraphy and dating of the Turkana sediments … We, and future generations will continue to benefit from his dedicated analyses and the resulting sound chronological sequence of the hominins, tools, and ancient faunas that we have recovered’.

The two examples represent the end members of a stellar career that laid down the gold standards for the successful methodology of the Ar dating methods. They also illustrate well his remarkable ability to identify important scientific problems that contributed, and are continuing to do so through his former students and colleagues, to understanding key problems in science: the evolution of the planet and the evolution of man. Few scientists have had the privilege to do so.

Ian was promoted progressively from Research Fellow to Fellow, Senior Fellow and Professor, the last in 1999 and a rather belated recognition by the ANU of his scientific contributions. Amongst other awards Ian was elected Fellow of the Geological Society of America in 1978 and Fellow of the American Geophysical Union in 1997. He was elected to the Australian Academy of Science in 1988 and, particularly pleasing to him, in 2007 was awarded their Jaeger Medal. He received an Honorary DSc from the University of Glasgow in 2009.

He retired in 2001 and was appointed Emeritus Professor and continued to work primarily on the Omo-Turkana Basin sequences of East Africa to establish the precise and accurate chronology until his laboratory was unceremoniously, and unbeknownst to him, dismantled by ANU bureaucrats who could neither solve a staffing problem nor recognise the immense contribution he had made to the ANU research reputation. Fortunately, the University of Queensland appointed him an Adjunct Professor that permitted him to further his work for a bit longer until ill health made that impossible.

During his tenure at ANU, he played an important role in the functioning of RSES through his always constructive participation in Faculty Board and in the scrupulous way he managed his research team. These were features that I particularly learned to appreciate during my 10 years as Director of the School. He and I may not always have agreed on all policy matters, but I could always be sure that his advice was the result of careful consideration of all views, free of any Machiavellian intent. 

His commitment to personal and institutional integrity and maintaining excellence at the highest international standards, wherever this may lie, were always foremost in the thinking and remained with him to the end.

He also played a significant part in the affairs of the Academy of Science through his contributions to many of its working committees and particularly on Council, where he served as Treasurer for four years. Here also, the above qualities, as well as possibly his Scottish heritage, served the Academy well.

In all areas, Professor McDougall’s contributions were outstanding and of lasting value. The way he conducted himself during his long scientific journey was exemplary. We have all much to learn from him.

He is survived by his wife Pam (Hodgson) and their three children, Scott, Geoffrey and Sandra.