School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada
Paul F. Hoffman was awarded the 2010 Walter H. Bucher Medal at the AGU Fall Meeting Honors Ceremony, held on 15 December 2010 in San Francisco, Calif. The medal is for “original contributions to the basic knowledge of the crust and lithosphere.”
Citation
Over the past 5 decades, Paul Felix Hoffman has profoundly changed our understanding of the origin and evolution of the continental crust and lithosphere by field mapping, regional synthesis and interpretation, and relentless hypothesis testing.
Paul has spent 48 seasons in the field and 25 of those in the Canadian Shield. For his Ph.D. studies at Johns Hopkins University and his early years at the Geological Survey of Canada (GSC), Paul worked on the spectacularly exposed rocks in the east arm of Great Slave Lake. Subsequently, he examined a transect across the Paleoproterozoic Coronation geosyncline and argued in several influential papers that plate tectonics was active at that time and remarkably similar to today’s regime. These papers are even more remarkable when we consider that it was at a time when modern—day plate tectonics had still not been widely accepted.
This work was followed by a decade of understanding the history of the Coronation geosyncline, later named Wopmay orogen. His earlier synthesis, based on reconnaissance, made a number of testable predictions, and Paul set out to falsify his own ideas. Paul recognized that the zonation of the belt could be interpreted in terms of a model involving rifting, passive margin subsidence, arc magmatism, and collision. He led teams of students, coworkers, and colleagues during an intense decade of investigation. When he published his first Wopmay synthesis, in 1980, Precambrian geology was mired in nonactualistic models for crustal evolution, with few based on detailed mapping and regional synthesis.
The lessons learned in Wopmay orogen and the recognition of the power of synthesis led Paul to expand his approach to the Precambrian of Laurentia and the history of supercontinents; his approach was transformative. Hoffman’s iconic map of Laurentia made it clear that the anastomosing Proterozoic orogenic belts between Archean cratons recorded the consumption of oceanic lithosphere, the collision of continental fragments, and the stabilization of large cratons underlain by cold, buoyant lithospheric mantle. The recognition of short—lived collisional events that produced a vast orogenic collage was a radical departure from crustal reworking and long—lived ensialic orogenesis in vogue over the previous decades.
Following his Laurentian synthesis, Paul went to Namibia to better understand Pan—African orogens and the amalgamation of Gondwana but was sidetracked by the remarkable juxtaposition of Neoproterozoic glacial deposits with platformal carbonates. Here Paul began a new phase of his career, applying the tools of field geology with isotope geochemistry, geochronology, and plate reconstructions to understanding Neoproterozoic Earth history. Within 2 years he was to develop the snowball Earth hypothesis to a level of detail way beyond Kirschvink’s original hypothesis. He built a comprehensive, multidisciplinary hypothesis that led to a series of landmark papers and perhaps, more important, set an example of how to integrate tectonics, climate science, biology, and geology for a new generation of scientists.
Overall, Paul Hoffman has had a profound influence on our understanding of the origin and evolution of continental lithosphere, from its early assembly to glaciation and weathering. He is richly deserving of AGU’s Walter H. Bucher Medal.
—SAMUEL A. BOWRING, Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge
Response
Thank you, Sam, for those memories; and thank you, AGU, for recognizing the fruits of field geology.
I was lucky to be born a buster. Busters were the generation before the boomers. There weren’t very many of us, yet opportunities were everywhere because of the postwar economic and demographic boom. It was easy for us to stand out and get ahead.
As a buster geologist, I was also lucky to be in the last generation that remembers the world before plate tectonics. I am proud that a geophysicist, Dick Gibb, and a team of geologists were soon able to independently confirm the deep antiquity of plate tectonics, in the Canadian Shield.
The work recognized here was done while I was at GSC, where I had the enthusiastic support of directors—general Yves Fortier, Digby McLaren, Bill Hutchison, and Ray Price. I was lucky that GSC granted me leaves without pay to teach for a term or a year at a time and that I was welcomed at University of California, Santa Barbara; California Institute of Technology; University of Texas at Dallas; and Lamont Doherty. I was lucky also that two midlevel managers, Bill Padgham and John McGlynn, in different government departments found resources to support many Ph.D. thesis projects in and around the area I was geologically mapping. Among the beneficiaries were Larry Aspler, Sam Bowring, Mike Easton, John Grotzinger, Robert Hildebrand, Todd Housh, Brad Johnson, Charlie Kerans, André Lalonde, Janet King, Dave McCormick, Brad Ritts, Gerry Ross, Marc St-Onge, Rein Tirrul, Mike Villeneuve, and my mapping projects. Sam mentioned “relentless hypothesis testing.” It’s true; the hypotheses were inspired by the mapping, and Sam did the relentless testing. Any proper tectonic model can be falsified with a few good dates.
I was luckiest of all when Lillian McGlynn convinced Erica Westbrook to give me a second look. Erica and I have been happily married for 34 years this month, despite moves that were mostly not of her own choosing. It was not luck that I got a lot done; I had help.
As students in the early 1960s, we were advised to steer clear of tectonics because it was “dead.” For those who follow advice better than I did, look for a field that’s dead. The longer it’s been dead, the better. With luck, it’s not dead; it’s dormant. If you can wake it up, you will have as much fun as I’ve had recently with snowball Earth.
—PAUL F. HOFFMAN, School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada