InCEES Assoc. Director published in PNAS

Looking at marine sediments to reconstruct past environmental conditions


David A. Fike

David A. Fike, associate professor in the Department of Earth and Planetary Sciences in Arts & Sciences, director of the Environmental Studies Program, and associate director of InCEES, was recently published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

The paper, entitled “Pyrite sulfur isotopes reveal glacial-interglacial environmental changes,” provides a novel approach to reconstructing ancient sea levels and ocean temperatures using microscopic minerals of pyrite (also known as fool’s gold) found in marine sediments.

Data about Earth’s past environmental conditions are essential for modeling current climate conditions, as well as predicting future changes to the climate.  However, it is often difficult to reconstruct key environmental parameters (such as sea level and temperature) from ancient history.  In this work, Fike’s lab identified a new way to extract this information from marine sediments using changes in the composition of pyrite.

“Historically, geologists use changes in the record of sedimentary pyrite to reconstruct changes in global ocean chemistry over very long periods of time,” said Fike. “During the last several years, our lab has questioned whether there might be additional environmental information in these records. In this paper we asked, what if the changes to the sulfur isotopes were influenced by local (and potentially rapidly changing) conditions, rather than more gradual global ocean processes?”

Working with colleagues at the Université Bretagne Occidentale in France, Fike’s lab examined sulfur isotopic records preserved in pyrite from sediments found in the Gulf of Lion off the Mediterranean coastline in France.  This area was specifically chosen because sediments were deposited there continuously over the past 500,000 years during the last five glacial-interglacial periods, each characterized by sea level changes in excess of 100 meters.

These new data show that pyrite sulfur isotopes can be a valuable tool for reconstructing local environments, which in turn gives modern scientists more insight into the history of the Earth’s conditions, and helps constrain models that predict future climate changes.  Fike plans to build on this work with a comprehensive survey of ocean sediments from around the world to fully explore the information present in this new proxy of past environmental conditions.