Rice scientist ready to study first cores from active continental rift

Rice’s Clint Miller ready to study first cores from Gulf of Corinth rift

By Linda Welzenbach
Special to Rice News

Rice geochemist Clint Miller is part of an international team of scientists that is collecting the first sediment samples ever drilled from Greece’s Gulf of Corinth, an active continental rift where Earth’s crust expands and thins.

“The Gulf is somewhat unique because it is an active rift that has oscillated over the last few million years between lake-like conditions and true marine conditions,” said Miller, a postdoctoral research associate in the Department of Earth, Environmental and Planetary Sciences. “Hopefully, we will be able to see this really clearly in the chemistry of the sediments we collect.”

Clint Miller

Clint Miller

Miller said scientists are especially interested in such continental rift zones because they are geologically active and often at risk for earthquakes and volcanic eruptions. “They also present a unique opportunity to observe plate tectonics in action,” he said.

Miller and colleagues sailed on the British Geologic Survey drilling vessel Fugro Synergy to collect samples from the Corinth rift in the Mediterranean Sea. The expedition is sponsored by the the International Ocean Discovery Program (IODP) and European Consortium for Ocean Research Drilling.

Having formed its modern expression over the past 5 million years, the Corinth rift is young for an active continental rift zone. It’s situated across a shallow marine basin about 30 miles west of Athens and has a closed drainage system that Miller said makes it ideal for studying early rift development and the way land forms when it is subject to competing forces from tectonics and climate.

The Gulf of Corinth as seen from the International Space Station

The Gulf of Corinth as seen from the International Space Station in 2011. (Photo courtesy of NASA)

The rift is spreading at a rate of about 10-15 millimeters per year, and rivers that drain into the Gulf carry sediments that partially fill the rift zone as it spreads. Miller said IOPD Expedition 381 differs from most scientific drilling missions because it aims to drill only three holes and to do so in a way that maximizes what scientists can learn.

He hopes drilling in carefully selected locations will enable them to collect sediment samples from across tens of thousands of years.

“From a paleoceanographic perspective, that is the best scenario for capturing reliable climate cycle information from seafloor sediments,” he said.

One of Miller’s tasks on ship will be to analyze the chemistry of water that is trapped in the pores of sediments that have been buried in the rift for up to 2 million years. Because the water was trapped inside the sediments as they were buried, it can help tell the story of the Gulf’s past.

IODP Expedition 381 logo“Pore water and ocean sediment tell how the climate and biosphere have changed over time,” he said. “From the types of organic carbon and related compounds that are present, we can get the rates of photosynthesis as well as the sediment and water chemistry of the past. That will tell us how life responded to the rift and to changing sea level.”

After the cruise, Miller will conduct more in-depth experiments at IODP’s core storage facility in Bremen, Germany.

Ultimately, Miller hopes to help address the hypothesis that environmental fluctuations preserved in the Corinth rift are related to 100,000-year climate cycles.

“We would like to know how the rift environment affects the deposition of carbon during glacial and interglacial time periods,” he said. “This will help us better understand how climate affects Earth’s biosphere, which is increasingly important due to human-induced climate change.”

To track the expedition’s progress or learn more, visit the IODP Expedition 381 blog.

–Linda Welzenbach is a science writer in the Department of Earth, Environmental and Planetary Sciences at Rice.

About Jade Boyd

Jade Boyd is science editor and associate director of news and media relations in Rice University's Office of Public Affairs.