Dr. Amy E. Kelly is a biogeochemist with a strong interest in analyzing and interpreting deep time lipid biomarker records that track the co-evolution of life and the environment across geologic time, particularly in the Precambrian and Early Paleozoic. She received a B.S. in Chemistry and Geochemistry from Caltech in 2002 and completed her Ph.D. in Organic Geochemistry at the Massachusetts Institute of Technology in 2009. She is currently a joint postdoctoral scholar at Arizona State University and UC Riverside. In addition to her research, she is dedicated to teaching and has mentored students at the Massachusetts Institute of Technology, Wellesley, UC Riverside and Arizona State University.
The sequence of events over the Neoproterozoic - Cambrian transition that led to the radiation of multicellular organisms has been an issue of debate for over a century. In her doctoral studies, Dr. Kelly set out to improve the understanding of environmental transitions during this key interval of Earth’s history by studying hydrocarbon biomarkers in Neoproterozoic to Cambrian aged sedimentary rocks and oils from Australia, Eastern Siberia and Oman. Biomarkers are hydrocarbons of ancient organisms that remain in the host rock, the structure and isotopic signatures of which can inform on the source organisms, depositional environment or even age of a rock. Together, this provides information on the environment and ecology of the time when the sediment that makes up the present day rock was deposited. She studied the distributions of steranes and other hydrocarbons through the various strata and characterized novel age and paleostratification biomarkers. Compound specific carbon isotopic data of two compounds classes, n-alkanes and isoprenoids, were also acquired and evaluated in the context of existing datasets with a focus on elucidating the processes responsible for anomalous trends. Consistent with the current theory, her results indicate that there was a significant shift in the redox state of the oceans in the Ediacaran and that this took place on a global scale. The biomarker and isotopic proxies measured help to further constrain the timing of this redox shift and suggest a concomitant switch in the composition of marine photosynthetic communities at the termination of the Neoproterozoic Era.
While her doctoral work focused on the rapid ecological transitions in the Neoproterozoic, her postdoctoral work integrates organic (biomarkers) and inorganic (sulfur isotopes, iron speciation and molybdenum isotopes) geochemical proxies to fully analyze the redox chemistry of the ancient oceans in order to unravel the co-evolution of the geosphere and biosphere in the mid-Proterozoic. By addressing the paleoredox, she hopes to reveal how eukaryotes survived and evolved in the calm immediately preceding the Neoproterozoic and the evolution of animals.
Her work addresses Goal 4 of the NAI roadmap: Understand how life on Earth and its planetary environment have co-evolved through geological time. The emerging story of the history of life on Earth is one in which abiotic environmental and geochemical parameters and biological processes shaped and forced one another through geologic time. Her work focuses on the earliest chapters of the history of eukaryotic life.
