Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2019 Jan 30;9(1):1003.
doi: 10.1038/s41598-019-38593-9.

87Sr/86Sr age determination by rapidly formed spherical carbonate concretions

Hidekazu Yoshida  1 , Yoshihiro Asahara  2 , Koshi Yamamoto  2 , Nagayoshi Katsuta  3 , Masayo Minami  4 , Richard Metcalfe  5
Affiliations

87Sr/86Sr age determination by rapidly formed spherical carbonate concretions

Hidekazu Yoshida et al. Sci Rep. .

Erratum in

Abstract

Isolated spherical carbonate concretions are frequently observed in finer grained marine sediments of widely varying geological age. Recent studies on various kinds of spherical carbonate (CaCO3) concretions revealed that they formed very rapidly under tightly constrained conditions. However, the formation ages of the isolated spherical carbonate concretions have never been determined. Here we use 87Sr/86Sr ratios to determine the ages of these spherical concretions. The studied concretions formed in the Yatsuo Group of Miocene age in central Japan. Some formed post-mortem around tusk-shells (Fissidentalium spp.), while other concretions have no shell fossils inside. The deformation of sedimentary layers around the concretions, combined with geochemical analyses, reveal that Sr was incorporated into the CaCO3 concretions during their rapid formation. Strontium isotopic stratigraphy using 87Sr/86Sr ratios of all concretions indicates an age of 17.02 ± 0.27 Ma, with higher accuracy than the ages estimated using micro-fossils from the Yatsuo Group. The results imply that the 87Sr/86Sr ratio of isolated spherical carbonate concretions can be applied generally to determine the numerical ages of marine sediments, when concretions formed soon after sedimentation. The 87Sr/86Sr age determinations have high accuracy, even in cases without any fossils evidence.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Ca and Sr distribution in and around the tusk-shell concretion. (a) Occurrence of a tusk-shell concretion formed around the mouth of a tusk-shell (Fissidentalium spp.) and, (b) a cross section through the tusk-shell showing the internal texture. (c,d) SXAM Ca and Sr X-ray intensity in and around the cut surface of a tusk-shell concretion. A sharp boundary between the concretion and matrix is also defined by the both elemental distribution. Index map is based on the data of Geospatial Information Authority of Japan website (http://www.gsi.go.jp/ENGLISH/index.html). Figures a–c are referred from Yoshida et al.. All photographs (a,b) shown here are taken by H. Yoshida.
Figure 2
Figure 2
Sr isotopic stratigraphy and numerical age determination by concretions. (a) Numerical age determined by Sr stratigraphy based on the well-known 87Sr/86Sr variations of seawater during the Paleogene to the present, with the accuracy within ±0.1~0.2 Ma. (b) The age of the tusk-shell concretions and concretions without fossils from Yatsuo Group lie within a narrow range of 17.02 ± 0.27 Ma based on the Sr isotopic stratigraphy. The centre, lower and upper lines (black, blue and red) show a best-fit line, lower-age and upper-age limits on the Sr-isotope curve, respectively.
See this image and copyright information in PMC

References

    1. Raiswell R. The microbiological formation of carbonate concretions in the Upper Lias of NE England. Chemical Geology. 1976;18:227–244. doi: 10.1016/0009-2541(76)90006-1. - DOI
    1. Dix GR, Mullins HT. Shallow, Subsurface growth and burial alteration of Middle Devonian calcite concretions. Jour. Sedimentary Petrology. 1987;57:140–152.
    1. Yoshida, H. et al. Early post-mortem formation of carbonate concretions around tusk-shells over week-month timescales. Scientific Reports5, 14123, 10.1038/srep14123 (2015). - PMC - PubMed
    1. Yoshida, H. et al. Generalized conditions of spherical carbonate concretions formation around decaying organic matter in early diagenesis, Scientific Reports, 8, 6308, 10.1038/s41598-018-24205-5 (2018). - PMC - PubMed
    1. Raiswell R. The growth of Cambrian and Liassic Concretions. Sedimentology. 1971;17:147–171. doi: 10.1111/j.1365-3091.1971.tb01773.x. - DOI

Publication types