This coal-forming period of geologic time is split into Mississippian & Pennsylvanian periods
[DOC] [TLE] The Carboniferous Period [PAR] The Mississippian and Pennsylvanian, in turn, are subdivided into a number of ... 
ideal conditions for the formation of coal, several major biological, geological, .... 
or disappearance of fauna usually marks the boundaries between time periods.