George Robert Tilton, former member of the Research Staff of both DTM and the Geophysical Laboratory, passed away in his sleep at the home of his daughter in Eugene, Oregon, on October 12. Tilton was best known for pioneering the uranium-lead isotopic method of determining the age of rocks, devising many of the basic analytical procedures and interpretive approaches still in use today.

With a Ph.D. in Chemistry from the University of Chicago, Tilton joined DTM in 1951. During his time at DTM, he worked with Tom Aldrich, George Wetherill, and Gordon Davis of the Geophysical Laboratory (GL). During this time, geochronology “came of age” and emerged from the realm of heroic analytical efforts and poorly understood “dates” to semi-routine analysis and interpretable “ages.” In 1956, Tilton transferred from DTM to GL and maintained close collaboration between the two departments. He left GL in 1965 to accept a position as Professor of Geochemistry at the University of California, Santa Barbara, where he served until 1991. Even after his retirement, Tilton remained very active in research.

His many honors included election to the National Academy of Sciences in 1977, president of the Geochemical Society in 1980, UCSB Faculty Research Lecturer in 1981, Honorary Doctor of Sciences degree from the Federal Institute of Technology in Zurich, Switzerland, in 1984, and Humboldt Foundation Awards for studies at the Max Planck Institute in Germany in 1989 and 1993.

In addition to his passions for his family and pursuing his research, George enjoyed classical music and spending time in the outdoors hiking and camping, plus the fellowship of his colleagues around the world. He was proud to have been the advisor to a wide array of graduate students from nearly every continent.

Tilton is survived by: his wife of 62 years, two daughters, two sons, seven grandchildren, and four great-grandchildren.

A memorial service will be held Saturday, October 23, in Santa Barbara. In lieu of flowers, donations may be sent to Hospice or a charity of your choice.