subcarboniferous

from The Century Dictionary.

• In geology, a name given by some geologists to the mountain-limestone division of the Carboniferous series, or that part of the series which lies beneath the millstone-grit. See carboniferous.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Geol.) Of or pertaining to the lowest division of the Carboniferous formations underlying the proper coal measures. It was a marine formation characterized in general by beds of limestone.