"I had been looking for rocks from this layer for many years - in most places the layer doesn't exist or has worn away," says Tarduno, a geophysicist who studies Earth's magnetic field. "We were walking along a ridge, and we spotted a layer between the brown volcanic rocks and the black marine shale. From a distance we knew that these rocks represented an environment we hadn't seen before. Once we reached them, we realized these were fine-grain sedimentary rocks ideal for preservation of fossils, and I bet the students we'd find fossils. Within five minutes one of my students pulled up a femur and said, "Like this?"

"It was one of those rare instances where you know immediately that what you're looking at has tremendous importance. It was clearly a vertebrate fossil - our guess was a large reptile, which would have required a relatively warm climate to survive."

The fossils locked in a record of what was happening in the Arctic just as extreme volcanism around the planet was winding down. Most of the volcanic activity didn't resemble spectacular eruptions like Mt. Pinatubo. Instead, the eruptions were "basaltic" - tons of lava oozed out, and carbon dioxide floated skyward. Besides huge amounts of lava in the Arctic, where hardened lava rock today measures more than a kilometer thick in some places, magma oozed from volcanoes in the Caribbean, in the Pacific Ocean northeast of Australia, in the Indian Ocean, off the coasts of Madagascar and Brazil, in South Africa and in the Southwestern United States.

Scientists have long considered the Cretaceous Period, which lasted from 144 to 65 million years ago, a warm time period and a possible model of the greenhouse effect, where gases like carbon dioxide collect in the atmosphere and trap in heat, causing global w
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Contact: Tom Rickey
trickey@admin.rochester.edu
716-275-7954
University of Rochester
17-Dec-1998