Electron microprobe study of magnesium distribution in some Mississippian echinoderm limestones from western Canada
Electron microprobe techniques were used to examine the distribution of Mg, Ca, and Fe in six samples of Mississippian skeletal and oolitic limestones from the Alberta Rocky Mountains. All samples show extremely low values of Fe. The following distributions of Mg (in wt % MgCO3) were observed: in four samples from the Loomis Member (Meramec) of the Mount Head Formation, echinoderm grains show highly variable Mg content averaging 1.11–1.43, whereas sparry calcite cement and the outer rings of ooids show much more uniform values averaging 0.73–0.84. In one sample from the Livingstone Formation (Osage), echinoderm grains show large Mg variation with a mean of 0.95; sparry calcite cement shows more uniform values with a mean of 0.50. A second, highly recrystallized sample from the Livingstone Formation has echinoderm grains which show large Mg variation with a mean of 0.43. The stroma canal structure characteristic of living echinoderms is not generally preserved in the grains. All of the echinoderm grains an...