Fig. 7: BSE images of echinoderm ossicles from Calhoun and Dalton coal balls.
From: A marine origin of coal balls in the Midland and Illinois basins, USA
Each image is from an echinoderm used in this study unless noted. a Well-preserved Calhoun ossicle showing HMC stereom in medium grey and LMC interstereom cement in light grey. The scale is 100 μm. b Relatively well-preserved Dalton ossicle fragment outlined in white, surrounded by LMC coal-ball cement at the top of the image. HMC stereom medium grey, LMC interstereom cement light grey, pyrite (P) white. The scale is 200 μm. c Relatively well-preserved Calhoun ossicle fragment outlined in white surrounded by LMC coal-ball cement. HMC stereom medium grey, LMC interstereom cement light grey, V, vugs in LMC interstereom cement. The scale is 200 μm. d Broken Dalton ossicle cut by gypsum vein (Gyp), not used in this study. HMC stereom (medium grey) filled with organic carbon (black), pyrite (P) (white) and small carbonate grains. The lower cross shows the location of EDS (energy-dispersive spectroscopy) analysis indicating HMC stereom. The upper cross shows the location of EDS analysis of a second ossicle fragment indicating HMC stereom. Strontium sulfate (Cel) dark grey. Scale is 300 μm. e Calhoun ossicle with Dickson type 1 (Gorzelak type 0) preservation on the rim and Dickson type 2 (Gorzelak type 2) preservation in the middle, HMC stereom medium grey, LMC interstereom cement light grey, dolomite (Dolo) dark grey (refs. 15,18). Scale is 200 μm; f Bored Dalton ossicle with stereom not used in this study. White Arrow indicates HMC stereom, cross shows location of EDS analysis indicating HMC stereom. The scale is 300 μm.
