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When did the Pennsylvanian Subperiod occur?
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Carboniferous Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the late Carboniferous Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The Pennsylvanian Subperiod occurred from 323.2 million to 298.9 million years ago. It represents the second major interval of the Carboniferous Period, following the Mississippian Subperiod.12