Table 2 Comparison of range in Mg/CaC mmol/mol for Pennsylvanian echinoderm ossicles and modern crinoid ossicles (ref. 39).

From: A marine origin of coal balls in the Midland and Illinois basins, USA

Locality

Age

Number of ossicles

Average Mg/CaC for locality (range) (mmol/mol)

Range Mg/CaC of ossicles by site (mmol/mol)

Average range of Mg/CaC analytic point values per ossicle (mmol/mol)

Dalton coal

Pennsylvanian

12

114 (105–126)

21

35

Calhoun Coal

Pennsylvanian

14

144 (130–198)

68

50

Bahama Banks*

Recent

41

145 (114–179)

65

89†

Suruga Bay*

Recent

45

142 (111–196)

85

131†

  1. *Data from Gorzelak et al. (ref. 39).
  2. †estimated by pairing highest wt% Ca with lowest wt% Mg and lowest wt% Ca with highest wt% Mg.
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