Fig. 6: Cross-plots of Na/CaC and Mg/CaC for coal-ball and echinoderm calcite.
From: A marine origin of coal balls in the Midland and Illinois basins, USA
The dashed line at 55 Mg/Ca separates LMC values to the left and HMC values to the right. Calhoun values are green and Dalton values are orange. a Coal-ball echinoderms and interstereom cement in mixed echinoderm-plant coal balls (circles) Mg/CaC of Pennsylvanian marine echinoderms (blue bar) (ref. 15). b Plant calcite in mixed echinoderm-plant coal balls (diamonds). c Plant calcite in plant-only coal balls (triangles). All ratios were reported in mmol/mol.
