A research group led by Professor Eiichi Yoshida of the Nagoya University Museum determines the geological age with high accuracy using the isotope ratio of strontium contained in the "spherical concrete" produced from sedimentary rocks deposited on the seabed. Especially successful for the first time in the world.
"Spherical concretion", a spherical block of calcium carbonate that is universally formed in sedimentary rocks, is very much due to the reaction between carbonic acid of biological origin and calcium ions in seawater after sedimentation of the stratum. It is known that it is formed quickly (in a few months to a few years).
This spherical concretion acts like a magnetic tape that takes in strontium from seawater and contains the strontium isotope ratio in the seawater at the time of deposition as it is, when it grows rapidly in the submarine strata.Since the strontium isotope ratio curve of seawater has already been established from the Cambrian period to the present age, this research group uses this to utilize the strontium isotope ratio during concretion and the formation age of concretion = formation of sedimentary strata. I tried to measure the age (geological age).As a result, the geological age can be obtained with about 100 times higher accuracy (error of about +/- 10 years) than the estimation using conventional fossils (usually with an error of about +/- 10 million years). It became clear.
This achievement not only makes it possible to determine the geological age with higher accuracy using concretion, but also makes it possible to measure the geological age by concretion even in sedimentary rocks around the world that do not produce fossils.In the future, it is expected to be widely applied and used in the fields of earth science and earth resource engineering as an unprecedented geological dating method.
Paper information:[Scientific Reports] 87Sr / 86Sr age determination by rapidly formed spherical carbonate concretions
