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Tribute to Bill Riedel from Ted Moore

There is so much you could point to in Bill’s career that was important to our knowledge of radiolarians and to science in general. But I would emphasize his first great achievement: the demonstration that radiolarians were stratigraphically useful. When the sediment samples from the Challenger expedition were studied, Ernst Haeckel published a definitive volume of beautifully illustrated radiolarian species. However, when the species found in the surface sediments of the Pacific Ocean were compared to earlier studies from marine deposits on land, it was found that many of the species in the surface sediments were also found in sections from the early Cenozoic. How could this be? There were only two possibilities: either the species of Radiolaria were very long lived,or a lot of erosion and reworking of the deep sea sediments was taking place. At that time the deep sea was viewed as a dark, very quiet environment with only the gentle tidal currents disturbing the environment. Clearly, the choice of the first explanation was the more reasonable: radiolarian species had been around, unchanged, for a very long time.

In 1954 A. S. Campbell published a small volume on Radiolaria In the Geological Society of America series “Treatise on Invertebrate Paleontology”. In it the author followed the dictum established by the study of the Challenger samples some 80 years earlier: Radiolaria were not useful for stratigraphic purposes; they were too long ranging. At almost the same time Bill Riedel, studying cores from the Swedish Deep Sea Expedition, proposed that they were useful for stratigraphy. They had clear first and last appearances. At SIO he combed through the large core collection there and identified key cores that sampled various parts of the Cenozoic section and contained sediments that were free of reworked microfossils. He went on to demonstrate several evolutionary lineages in the Radiolaria. As a graduate student at SIO from 1963 – 68 I studied samples from these cores and began to see the great potential of this highly diverse fauna for improving stratigraphic resolution. And shortly thereafter, with the advent of the Deep Sea Drilling Project, Bill and the many students and fellow scientists that he mentored were ready to take advantage of this treasure trove of samples.

Ted Moore
Professor Emeritus
Department of Earth and Environmental Sciences
University of Michigan

Photo from 2008 of Bill and Elizabeth next to Bill’s "family tree".