People: Astrobiology Graduate Student Directory

Ken Williford
Earth & Space Sciences

I was drawn to astrobiology by my longstanding desire to explore the fundamental nature of life in the universe. I have always been most comfortable, productive, and inspired working in an interdisciplinary environment, and astrobiology offers this. My primary research area is the biogeochemistry of mass extinctions, but I work and communicate regularly with faculty and students across widely varying disciplines including astronomy, biology, microbiology, geology, geophysics, oceanography, and atmospheric science.

The oldest fossil traces of complex animals, branched burrows and small shelly fossils in rocks about 540 million years old, mark the beginning of the Phanerozoic Eon, or the "time of visible life." This evolutionary breakthrough and the diversification of shelled animals that followed allowed early geologists to erect a time scale of Earth history based on major changes in the fossil record. Five times over the last 500 million years, over half of the animal species on the planet have abruptly disappeared. These events have come to be known as the "big five" mass extinctions.

The record of microbial life on Earth extends into the oldest sedimentary rocks on the planet and covers nearly 90% of Earth history. The microbial biosphere plays a primary role in the mediation of the biogeochemical cycles that determine the state of planetary habitability for more complex organisms. By contrast, the record of complex, multicellular life covers just more than 10% of Earth history. This is a very important 10% in terms of understanding the evolution of Earth systems on million year time scales, however, as younger rocks are more common, better preserved, and more easily correlated across time and space than rocks deposited before the Phanerozoic.

Mass extinctions represent intervals of Earth history when planetary habitability for multicellular life was drastically reduced, yet microbial life continued to flourish. What was the role of the microbial biosphere in the onset and persistence of, and the recovery from mass extinction conditions? What are the relationships between microbial and multicellular habitability on Earth? I use diverse techniques in biostratigraphy, isotope and organic geochemistry to gain insight into these questions.

Triassic ammonite fossil in cross section
showing microbial encrustation

Publications

Williford, K.H., Ward, P.D., Garrison, G.H., Buick, R., 2007. An extended stable organic carbon isotope record across the Triassic-Jurassic boundary in the Queen Charlotte Islands, British Columbia, Canada. Palaeogeography, Palaeoclimatology, Palaeoecology 244(1-4): 290-296.

Ward, P.D., Garrison, G.H., Williford, K.H., Kring, D., Goodwin, D., Beattie, M., McRoberts, C., 2006. The organic carbon isotopic and paleontological record across the Triassic-Jurassic boundary at the candidate GSSP section at Ferguson Hill, Muller Canyon, Nevada, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 244(1-4): 281-289.