New Method of Dating Oceanic Crust Is Most Accurate So Far

October 31, 2005
New Method of Dating Oceanic Crust Is Most Accurate So Far

A newly developed method that detects tiny bits of zircon in rock reliably predicts the age of ocean crust more than 99 percent of the time, making the technique the most accurate so far.

Image: Tiny crystals called zircons, used to date oceanic crust, are relatively common in rocks known as gabbros. Credit: Michael John Cheadle, University of Wyoming

After collecting zircon-bearing samples of ocean crust, the scientists used a Sensitive High Resolution Ion Micro Probe (SHRIMP) to determine the absolute ages of 17 samples from Atlantis Bank about 75 miles south of the Southwest Indian Ridge in the southern Indian Ocean. About 25 percent of the samples were 2.5 million years older than predicted by conventional models of crust generation at mid-ocean ridges.

"This research advances our understanding of how oceanic crust is formed, and the processes involved in that formation," says Mike Cheadle, geologist at the University of Wyoming (UW) and coauthor of an article describing the technique in the Oct. 28 issue of the journal Science.

Zircons are widely regarded as providing the best basis for finding the absolute age of rocks on land, according to Cheadle's coworker, Barbara John, who is also geologist at UW. The zircon dating technique has been used extensively to answer questions such as when and how fast the Earth's continental crust forms. But until now, scientists have relied on geophysical methods based on magnetism to date ocean crust.

As the Earth's tectonic plates separate over time, new crust is created at mid-ocean ridges, says John. Minerals in the rocks that make up the crust are magnetized in the direction of the Earth's magnetic field as they cool and freeze. Because the field reverses polarity over time, the rocks record the polarity, creating alternating stripes on either side of a mid-ocean ridge.

Traditionally, instruments aboard ships have predicted the age of the ocean's crust by mapping these magnetic stripes, and then calculating an age using distance and time between polarity reversals within the crust, says Rodey Batiza, program director in the National Science Foundation (NSF)'s Division of Ocean Sciences, which funded the research. But that method does not reveal the entire process involved in the growth of ocean crust, he says.

Joshua Schwartz, the paper's first author and a UW Ph.D. candidate in geology, says the team's research offers another tool to understand the complex processes occurring beneath the Earth's surface. "Our finding that these zircons are older than they should be relative to their magnetic age alters what we've thought about oceanic crust, he says. "The ability to date zircons in ocean crust offers another and better way to determine how ocean crust is formed."

Adds Cheadle, "Findings about today's ocean ridges help us to better understand how the Earth has worked in the past."

Other co-authors of the paper are affiliated with the U.S. Geological Survey in Menlo Park, Calif., and the Woods Hole Oceanographic Institution in Woods Hole, Mass.

Source: NSF

Explore further: Dawn finds possible ancient ocean remnants at Ceres

Related Stories

Dawn finds possible ancient ocean remnants at Ceres

October 26, 2017

Minerals containing water are widespread on Ceres, suggesting the dwarf planet may have had a global ocean in the past. What became of that ocean? Could Ceres still have liquid today? Two new studies from NASA's Dawn mission ...

Study bolsters theory of heat source under Antarctica

November 8, 2017

A new NASA study adds evidence that a geothermal heat source called a mantle plume lies deep below Antarctica's Marie Byrd Land, explaining some of the melting that creates lakes and rivers under the ice sheet. Although the ...

When continents break it gets warm on Earth 

November 13, 2017

The concentration of carbon dioxide (CO2) in the atmosphere determines whether the Earth is in greenhouse or ice age state. Before humans began to have an impact on the amount of CO2 in the air, it depended solely on the ...

Recommended for you

Cells lacking nuclei struggle to move in 3-D environments

January 20, 2018

University of North Carolina Lineberger Comprehensive Cancer Center researchers have revealed new details of how the physical properties of the nucleus influence how cells can move around different environments - such as ...

Information engine operates with nearly perfect efficiency

January 19, 2018

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine's efficiency ...

New research challenges existing models of black holes

January 19, 2018

Chris Packham, associate professor of physics and astronomy at The University of Texas at San Antonio (UTSA), has collaborated on a new study that expands the scientific community's understanding of black holes in our galaxy ...

Team takes a deep look at memristors

January 19, 2018

In the race to build a computer that mimics the massive computational power of the human brain, researchers are increasingly turning to memristors, which can vary their electrical resistance based on the memory of past activity. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.