The Pennsylvanian is a geologic (sub)period lasting from roughly 325 million years before the present to 286 million years before the present. As with most older geologic periods, the rock beds that define the start and end are well identified, but the exact date of the start and end of the period are uncertain by a few million years. In North America where the early Carboniferous beds are primarily marine limestones, it is treated as a full fledged geologic period between the Mississippian and the Permian. The Pennsylvanian is the upper part of the Carboniferous in North America. In Europe, the Mississippian and Pennsylvanian are one more or less continuous sequence of lowland continental deposits and are lumped together as the Carboniferous Period. Refer to the Carboniferous Period article for further information on faunal stages and climate.