An improved age for Earth's latest magnetic field reversal using radiometric dating

July 7, 2015
A photograph of the geological section across the Matuyama-Brunhes boundary in Chiba Prefecture, Japan. (a) Overview of the Chiba section. (b) and (c) Detail of a volcanic ash layer (Byk-E) just below the MBB in the Chiba section. The length of the ruler (b) and diameter of the coin (c) are 1.25 m and 2 cm, respectively. Credit: NIPR/Ibaraki University/JAMSTEC

The Earth's magnetic field periodically reverses such that the north magnetic pole becomes the south magnetic pole. The latest reversal is called by geologists the Matuyama-Brunhes boundary (MBB), and occurred approximately 780,000 years ago. The MBB is extremely important for calibrating the ages of rocks and the timing of events that occurred in the geological past; however, the exact age of this event has been imprecise because of uncertainties in the dating methods that have been used.

A team of researchers based in Japan and Canada have obtained an improved age for the MBB. The team studied that was deposited immediately before the MBB. This volcanic ash contains small crystals called zircons. Some of these crystals formed at the same time as the ash; thus, radiometric dating of these zircons using the uranium-lead method provided the exact age of the . To verify their findings, the researchers also used a different method to date sedimentary rock from the same place that was formed at the time of the MBB. The combined results demonstrate that the age of the MBB is 770.2 ± 7.3 thousand years ago. The research has been published in the journal Geology.

Dr. Yusuke Suganuma of the National Institute of Polar Research, Tokyo, who is the lead author on the paper, commented: "This study is the first direct comparison of radiometric dating, dating of sediments, and the geomagnetic reversal for the Matuyama-Brunhes boundary. Our work contributes calibrating the , and will be extremely important in future studies of the events that occurred at this time."

Explore further: Earth's magnetic field could flip within a human lifetime

Related Stories

Jeju Island is a live volcano, study reveals

July 22, 2014

In Jeju, a place emerging as a world-famous vacation spot with natural tourism resources, a recent study revealed a volcanic eruption occurred on the island. The Korea Institute of Geoscience and Mineral Resources (KIGAM) ...

The ashes of Mt. St. Helens

June 26, 2015

The massive eruption of Mt. St. Helens 35 years ago is one of the largest ever seen in North America. LMU volcanologists now report a retrospective analysis of salts leached from the ash deposited by the volcano on that occasion.

Researchers narrow birth estimate for the Takliman Desert

June 12, 2015

The second largest sand sea in the world, the Takliman Desert in central Asia influences geology, the global climate, and has even shaped the development of global human culture—the two branches of the Silk Road along its ...

Dating an ancient episode of severe global warming

June 15, 2011

Using sophisticated methods of dating rocks, a team including University of Southampton researchers based at the National Oceanography Centre, Southampton, have pinned down the timing of the start of an episode of an ancient ...

Recommended for you

Scientists examine bacterium found 1,000 feet underground

December 8, 2016

Pioneering work being carried out in a cave in New Mexico by researchers at McMaster University and The University of Akron, Ohio, is changing the understanding of how antibiotic resistance may have emerged and how doctors ...

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.