Greg Retallack

Gregory John Retallack (November 8, 1951) is an Australian paleontologist, geologist, and author who specializes in the study of fossil soils (paleopedology). His research has established the fossil record of soils though major events in Earth history, extending back some 4.6 billion years. He is the author or editor of more than 10 books and over 230 referred scientific papers, including two standard paleopedology textbooks.
“Whereas there has been a community of scholars engaged in the study of Quaternary paleosols, impetus for the study of pre-Quaternary paleosols largely originated with Dr. Gregory Retallack at the University of Oregon."
"Retallack has literally written the book on ancient soils."
Retallack moved with his family from Hobart, Tasmania at age 4. He grew up in Hurstville and then Epping, in the suburbs of Sydney, New South Wales. His father Kenneth John Retallack (1926-1969) was CEO of a print-engraving business, and his mother Wendy (nee Dean) Retallack (born 1928), an artist and homemaker. He attended the King’s School (Parramatta), then studied biology and paleontology at Macquarie University. He received a BSc Hons with University Medal in 1974 from the and a Ph.D. in 1978 in geology from the same university. After a postdoctoral fellowship at Indiana University he joined the faculty at the University of Oregon in 1981. He has been a professor in the Department of Geological Sciences since 1992, and Director of the Condon Collection of the University of Oregon Museum of Natural and Cultural History since 2009.
Retallack was 1973 and 1975 Australian Intervarsity 24-hour orienteering (rogaining)champion. An avid ski tourer and mountaineer: his major ascents include Mount Aspiring and Mount Tutoko (New Zealand), Matterhorn (Switzerland), Mont Blanc (France), Mount Kenya (Kenya), Kilimanjaro (Tanzania), Huamanripayoc Cordillera Vilcabamba (Peru), Grand Teton and Mount Jefferson(USA) and Graphite Peak (Antarctica).
A keen fossil collector since the age of 6, Retallack was outspoken concerning heavy-handed federal seizure in 1993 of the skeleton of Tyrannosaurus rex excavated by Pete Larson. This effort to restrict commercial fossil collecting backfired when “Sue” was sold at auction for $8 million, stimulating a dinosaur gold rush.
Evolution of life on land
Retallack discovered as a teenager that paleosols were preserved among fossil roots below some kinds of fossil plant horizons, and that paleosols could reveal aspects of plant communities difficult to infer from the fossil plants themselves. This novel approach to reconstructing life on land could be applied to understanding major events in evolution, sometimes supplementing and sometimes challenging prior understanding. Initial work was on Triassic vegetation and climate. Later construction of Cenozoic paleoclimate time series led to the idea that grassland-grazer coevolution was responsible for climatic cooling over the past 50 million years, which has implications for biosequestration of carbon. Fieldwork in Kenya on paleosols associated with apes (Proconsulidae) ancestral to humans revealed that the evolutionary transition to upright stance occurred in woodlands rather than savannas. Paleosols of the Cretaceous-Paleogene boundary in Montana implicated abrupt paleoclimatic change and acid rain from extraterrestrial impact in the extinction of dinosaurs
Work on the Permian-Triassic boundary in Antarctica lead to formulation of an hypothesis of greenhouse crisis due to methane outburst associated with flood basalt in this greatest of all mass extinctions
Devonian fossil soils at sites for tetrapods suggest a woodland hypothesis for the evolutionary transition from fish to amphibian. Discovery of fossil soils at classical South Australian sites for the Ediacara biota are evidence that these fossils formerly regarded as marine were instead terrestrial organisms such as lichens, slime molds and microbial colonies”
A Paleoproterozoic paleosol with problematic fossils comparable with living Geosiphon demonstrate a long evolutionary history for life on land”
Such ancient and complex life on land supports the view that life may originated in soil.
Retallack’s work on Late Permian mass extinction and Science Channel USA’s “Miracle Planet” episode “Death and Rebirth” . His work on Miocene of Panama was featured in National Geographic Channel USA’s “Terror Raptor” episode of “Prehistoric predators”. Radio interviews concerning his recent work on early life on land , Bob McDonald for Canadian Broadcast Corporation and Dave Miller for Oregon Public Broadcasting
In a challenge to young earth creationism, Retallack debunked interpretation of the fossil forests of Yellowstone National Park as deposits of volcanic lahars in which tree trunks landed upright, by showing that the fossil stumps were rooted in moderately developed paleosols. Because moderate development of soils can take as long as 5000 years, only a few paleosols in succession are needed to exceed the young earth creationism age of the Earth, and at Yellowstone there are at least 24 successive fossil forests. Sequences of paleosols remain the most obvious tangible evidence against young earth creationism.
In addition to paleopedology, Retallack continues research in paleobotany. His special interests include Triassic fossil plants such as Pleuromeia, Isoetes, Dicroidium and Lepidopteris. With David Dilcher he developed a coastal hypothesis for the dispersal and rise to dominance of angiosperms . Retallack also developed new techniques for using stomatal index of fossil Ginkgo leaves to obtain past atmospheric carbon dioxide . This work led to the concept of paleoenvironmental regulation by the Proserpina Principle: plants cool the planet, whereas animals warm it.
Retallack’s name is honored by several fossils including Cladophlebis retallackii, fossil fern foliage and Hypisodus retallacki, a fossil mouse deer.
In a study of soils at 84 temples of Classical Greece, Retallack discovered that each deity and cult was associated with a particular kind of soil, suggesting an economic basis for Greek polytheism. Dionysos and Demeter, for example, were gods of farming, Hermes and Hera gods of pastoralists and Apollo and Artemis gods of nomadic hunter-gatherers
* Soils of the past: an introduction to paleopedology, 2nd edition, Blackwell, Oxford, 2001, ISBN 0-632-05376-3
* A colour guide to paleosols, John Wiley and Sons, Chichester, 1997, ISBN 0-471-96711-4
Selected publications
* Retallack, G.J. and Feakes, C.R., 1987. Trace fossil evidence for Late Ordovician animals on land. Science, v. 235, p. 61-63.
* Retallack, G.J., Dugas, D.P. and Bestland, A.E., 1990. Fossil soils and grasses of the earliest East African grasslands. Science, v. 247, p. 1325-1328.
* Retallack, G.J. and Germán-Heins, J., 1994. Evidence from paleosols for the geological antiquity of rain forest. Science, v. 265, p. 499-502.
* Retallack, G.J., 1995. Permian-Triassic life crisis on land. Science, v. 267, p. 77-80.
* Retallack, G.J., 1997. Early forest soils and their role in Devonian global change. Science, v. 276, p. 583-585.
* Retallack, G.J., 2001. A 300 million year record of atmospheric carbon dioxide from fossil plant cuticles. Nature, v. 411, p. 287-290.
* Retallack, G.J., 2008. Rocks, views, soils and plants at the temples of ancient Greece. Antiquity, v. 82, p. 640-657.
* Retallack, G.J. 2013. Ediacaran life on land. Nature, v. 493, p. 89-92.
Retallack has served as an associate or technical editor for such scientific journals as Geology, Palaios, and Journal of Sedimentary Petrology. His fellowships include the Geological Society of America, and the American Association for the Advancement of Science.
He served as the president and vice president of the Cordilleran Section of the Paleontological Society, of the Oregon Academy of Sciences, and of the University of Oregon Chapter of the Society of Sigma Xi.
Critical reception
Early reviews of Retallack’s now-classic textbooks conclude that they are indispensable for paleopedology. Of “Soils of the past”, David Fastovsky concludes “it is requisite for all persons trying to understand paleosols”. Of “A colour guide to paleosols”, Daniel Yaalon concludes “Highly recommended for students and researchers alike for an introductory insight to paleopedology and to whet and refine their skills in paleosol interpretation.” Both reviews however baulked at the unfamiliarity of soil science terminology and classification in these texts.
Retallack’s approach to the description and interpretation of paleosols has been widely adopted., but Retallack’s approach has since been validated by development of additional geochemical proxies for soil taxonomic criteria. Retallack’s confirmation of abrupt paleoenvironmental change on land at the Cretaceous-Tertiary was questioned for its applicability to all Ediacaran fossils. Later work on growth and preservation of the Ediacaran fossil Dickinsonia was unchallenged. Recent discovery that Ediacaran fossils were preserved in paleosols and thus could not be marine fossils, but disputed in others.
Awards and honors
Retallack has been honored for his research, including the Stillwell Award of the Geological Society of Australia, for best paper in the society journal in 1977, and the Antarctic Medal of the U.S. National Science Foundation in 1999. He has been an invited lecturer throughout the U.S., and also to Germany, England, China, Thailand and India.
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