Carboniferous: of, belonging to, or denoting a geologic division of the Paleozoic Era following the Devonian and preceding the Permian.

石炭纪的，石炭系的：(属于或表示)地质上的一个分段，即紧跟着泥盆纪而早于二叠纪的古生代的。

youdao

Coal is found in many more places a whole geological era's worth of rocks, those of the Carboniferous, are named in its honour and it cannot be pumped around, but can be crushed and burned and so produces baseload power.

ECONOMIST: Unconventional gas