Submitted by: Odio @ 08:23 PM | Friday, December 16, 2016 | (url: http://phys.org/n...)
Mother-of-pearl or nacre (pronounced nay-ker), the lustrous, tough-as-nails biomineral that lines some seashells, has been shown to be a faithful record of ancient ocean temperature.
Writing online Thursday, Dec. 15, in the journal Earth and Planetary Science Letters, a team led by University of Wisconsin-Madison physics Professor Pupa Gilbert describes studies of the physical attributes of nacre in modern and fossil shells showing that the biomineral provides an accurate record of temperature as the material is formed, layer upon layer, in a mollusk.
"We can very accurately correlate nacre tablet thickness with temperature," says Gilbert, explaining that mother-of-pearl is formed as mollusks lay down microscopic polygonal tablets of the mineral aragonite like brickwork to build layers of the shiny biomineral.
The work is important because it provides scientists with a new and potentially more accurate method of measuring ancient ocean temperatures, improving on methods now used with other biominerals to tease out the record of the environmental conditions at which the materials formed in the distant past.
"Everyone else measures temperatures in the ancient world using chemical proxies," says Gilbert, referencing methods that, for example, use ratios of isotopic oxygen locked into tiny fossil shells made by marine microorganisms known as Foraminifera to get a snapshot of ocean temperatures in the distant past.