Figure 1
From: 87Sr/86Sr age determination by rapidly formed spherical carbonate concretions
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.3. All photographs (a,b) shown here are taken by H. Yoshida.
