BLOOMINGTON, Ind. -- Ancient rocks from the bottom of the Pacific Ocean suggest dramatic climate changes during the dinosaur-dominated Mesozoic Era, a time once thought to have been monotonously hot and humid.
In this month's Geology, scientists from Indiana University Bloomington and the Royal Netherlands Institute for Sea Research present new evidence that ocean surface temperatures varied as much as 6 degrees Celsius (about 11 degrees Fahrenheit) during the Aptian Epoch of the Cretaceous Period 120 million years ago.
The finding is relevant to the ongoing climate change discussion, IUB geologist Simon Brassell says, because it portrays an ancient Earth whose temperatures shifted erratically due to changes in carbon cycling and did so without human input.
"Combined with data from the Atlantic, it appears clear that climate changes were taking place on a global scale during this time period," said Brassell, who led the study.
A previous study from an Atlantic Ocean site had suggested a changeable climate around the same time period. But it was not known whether the Atlantic data indicated regional climate change unique to the area or something grander.
"We had virtually no data from the middle of the largest ocean at that time period," Brassell said. "The data we collected suggest significant global fluctuations in temperature."
As part of the National Science Foundation's Ocean Drilling Project, the geoscientists voyaged in 2001 to Shatsky Rise, a study site 1,600 kilometers (1,000 miles) east of Japan and 3,100 meters below the ocean surface. Shatsky Rise is known to have formed at the end of the Jurassic Period immediately prior to the beginning of the Cretaceous, the last period of the Mesozoic Era.
The scientists' vessel, the JOIDES Resolution, is specially outfitted with a drill that can be lowered to the sea floor for the collection of rock samples.