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American geologist From Wikipedia, the free encyclopedia
Julia Ann “Jan” Tullis was an American structural geologist and emerita Professor at Brown University. Tullis is known for her work in structural geology, especially for her experimental work in deformation mechanisms, microstructures, and rheology of crustal rocks.
Julia Ann ("Jan") Tullis | |
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| Born | Julia Ann Tullis February 21, 1943 Swedesboro, New Jersey, U.S. |
| Died | September 15, 2024 (aged 81) Providence, Rhode Island, U.S. |
| Nationality | American |
| Alma mater | Carleton College (A.B.) University of California, Los Angeles (PhD) |
| Known for | Deformation Mechanics |
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| Thesis | Preferred orientations in experimentally deformed quartzites (1971) |
| Doctoral advisor | David T. Griggs, John Christie |
| Doctoral students | Greg Hirth |
Tullis graduated Magna Cum Laude with distinction from Carleton College in June 1965,[1] earning her A.B. in Geology. Following this she completed her PhD at the University of California, Los Angeles in 1971 with a thesis on experimental rock deformation. Tullis became a research assistant at Brown University while editing her dissertation in 1970. Later, Tullis was named a Research Assistant Professor in 1971, Associate Professor in 1979, and a full Professor in 1989.[2] She transitioned to Professor Emerita in 2013 but continued with undergraduate teaching and advising right up to her death in September 2024.[3]
Tullis' research involved experimental investigations of the deformation mechanisms, microstructures and rheology of crustal rocks using constant strain-rate Griggs-type solid medium apparatus including adaptations for molten salt assemblies.[4] Her two major goals were to enable more accurate inferences concerning the thermomechanical history of naturally deformed rocks based on their preserved microstructures and crystallographic preferred orientations, and to provide mechanical data and flow laws to enable more accurate modeling of crustal deformation under various conditions.[5]
Experiments were conducted on monophase and polyphase aggregates, both natural and synthetic, over a wide range of pressure and temperature conditions equivalent to those from the shallow to the deep crust, and involving varying controlled water contents. She and her students and other collaborators documented grain-scale Deformation mechanisms from brittle fracturing to cataclastic flow to dislocation creep and melt or fluid-enhanced diffusion creep.[6] These experiments investigated the role of phase distribution and contiguity in the progressive deformation of polyphase aggregates, and documented a number of processes resulting in strain weakening and localization, such as in mylonite zones.[7] Tullis' work with Renee Heilbronner examined fabric evolution during progressive shearing and static annealing.[8]
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