Renne Receives 2005 N. L. Bowen Award

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Paul Renne received the N.L. Bowen Award on 6 December 2005 from the Volcanology, Geochemistry, and Petrology Section at the 2005 AGU Fall Meeting in San Francisco, Calif. The award recognizes outstanding contributions to volcanology, geochemistry, or petrology. Paul Renne photo

Citation

It is a great pleasure to offer this citation of my good friend Paul Renne. I want to describe Paul’s rigorous and thoughtful approach to science, as illustrated in a remarkable series of papers that simultaneously drove developments in argon (Ar) geochronology and contributed to a fascinating scientific problem.

One of Paul’s enduring interests is flood basalts. How do these massive eruptions originate? Do they result solely from rifting, or are the heads of mantle plumes involved? Do flood basalts coincide with mass extinctions, and if so, can causality be proved or disproved? How can geochronology help answer such questions?

Prior to Paul’s work, the Siberian Traps were thought to have erupted over millions of years, sometime near the Permian-Triassic extinctions. In 1991, Paul reported 40Ar/39Ar ages refuting this view: A key sequence of Trap lavas erupted with very high effusion rates, as expected for a mantle plume origin. Determination of accurate rates requires high-precision analyses. And his results speak for themselves in terms of precision: They are extraordinary, attesting to the analytical skill developed at the Berkeley Geochronology Center.

To establish a relationship between flood basalts and mass extinctions requires accuracy as well, for example, to compare an Ar age of a trap flow with zircon ages of ash beds near the extinction boundary. But Ar ages suffer from complications that can cause inaccuracy, and in his work on the Permian-Triassic boundary one senses Paul’s frustration with this limitation.

In the short term, he found a way to sidestep this issue, by Ar-dating bentonites bracketing the boundary. These ages show, that to within a few hundred thousand years of uncertainty, the eruption and the extinctions were coincident, permitting causality. In the longer term, Paul sought to identify and reduce systematic error in 40Ar/39Ar ages. Through compilation of numerous age standard analyses, he effectively eliminated intercalibration as an error source. From his rigorous error propagation formulae, Paul identified another critical source of systematic error: the 40K (potassium-40) decay constant. For several years he has worked to find natural samples of independently known age from which the decay constant can be deduced. This quest continues and is now having an impact in uranium/lead geochronology as well, as the debate over uncertainty spreads to other methods.

For his contributions to Ar geochronology and to our understanding of flood basalts, and for contributions to hominid evolution studies I have not mentioned, Paul Renne richly deserves this award.

—K. A. Farley, California Institute of Technology, Pasadena

Response

I am especially gratified to receive this citation from Ken Farley, one of the truly outstanding Earth scientists of my generation. I am humbled to share this recognition with the great scientists who have previously won the N.L. Bowen Award, many of whom have influenced me deeply over the years.

I am honored to be associated in some way with Norman L. Bowen. I learned about Bowen’s work from my first geology teacher, at Lassen College, in Susanville, Calif. Probably none here tonight have ever heard of Martin S. Peterson, but he was an extraordinary teacher who first kindled my interest in geology.

I had many important mentors as a student—both undergraduate and graduate—at the University of California, Berkeley, including George Brimhall, Ian Carmichael, Garniss Curtis, Dick Hay, Hal Helgeson, and Rudy Wenk. I am fortunate to continue my association with some of these mentors as current colleagues, along with others such as Don DePaolo and Mark Richards, who came to Berkeley after I finished my Ph.D.

Among the Berkeley faculty who nurtured my scientific and professional growth, Ian Carmichael was particularly influential. Along with his scientific mentorship, Ian introduced me to my wife, Brooke, who has enriched my life in many ways and who herself deserves thanks for helping to enable my career.

As a postdoc at Princeton University, N.J., I learned 40Ar/39Ar geochronology from Tullis Onstott, before he became a geomicrobiologist. At Princeton, I was exposed to some exciting ideas about the origins and consequences of flood basalts by Jason Morgan. Unfortunately, the importance of Jason’s ideas eluded me at the time. After all, coming from Berkeley I knew what caused mass extinctions. It was not until several years later, when Asish Basu introduced me to the Siberian Traps, that I really got involved in this topic.

Despite working in Garniss Curtis’s K-Ar lab as a Ph.D. student, during a time in which some exciting work in dating hominids was being done right under my nose, I was largely oblivious to the topic until I returned to Berkeley in 1990. Subsequently I have been fortunate to collaborate extensively with the great paleoanthropologist Tim White in refining the picture of hominid evolution over the past six million years.

I must acknowledge the extraordinary support of my colleagues at the Berkeley Geochronology Center: Tim Becker, Alan Deino, Abed Jaouni, Ken Ludwig, Roland Mundil, Warren Sharp, and Lisa Smeenk. I also thank the Ann and Gordon Getty Foundation and the U.S. National Science Foundation for their support.

—Paul Renne, Berkeley Geochronology Center, Calif.