New data on the formation of Carboniferous coal balls
One third (27/82) have coal balls, including 57% of major cycles, 36% of intermediate cycles and 16% of minor cycles. Coalball occurrence in the Donets Basin is similar: over an interval of about 4 (~315311 Ma, latest Bashkirian to midMoscovian), 39% (11/28) of transgressiveregressive cycles have coal balls. ...