Pennsylvanian (geology)

Pennsylvanian
323.2 ± 0.4 – 298.9 ± 0.15 Ma PreꞒ Ꞓ O S D C P T J K Pg N
A map of Earth as it appeared 310 million years ago during the Pennsylvanian Subperiod, Moscovian Age
Chronology
−360 — – −355 — – −350 — – −345 — – −340 — – −335 — – −330 — – −325 — – −320 — – −315 — – −310 — – −305 — – −300 — – Paleozoic Devonian Carboniferous Permian Mississippian Pennsylvanian Early Middle Late Early Mid Late Tournaisian Viséan Serpukhovian Bashkirian Moscovian Kasimovian Gzhelian     ← Carboniferous Rainforest Collapse ← Mazon Creek Fossils ← End of Romer's Gap ← Start of Romer's Gap Subdivision of the Carboniferous according to the ICS, as of 2023.[1] Vertical axis scale: Millions of years ago
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Subperiod
Time span formality	Formal
Lower boundary definition	First appearance of the Conodont Declinognathodus nodiliferus.
Lower boundary GSSP	Arrow Canyon, Nevada, United States 36°44′00″N 114°46′40″W / 36.7333°N 114.7778°W / 36.7333; -114.7778
Lower GSSP ratified	1996[2]
Upper boundary definition	First appearance of the Conodont Streptognathodus isolatus within the morphotype Streptognathodus wabaunsensis chronocline.
Upper boundary GSSP	Aidaralash, Ural Mountains, Kazakhstan 50°14′45″N 57°53′29″E / 50.2458°N 57.8914°E / 50.2458; 57.8914
Upper GSSP ratified	1996[3]

The Pennsylvanian (/ˌpɛnsəlˈveɪni.ən/ pen-səl-VAYN-i-ən,^[4] also known as Upper Carboniferous or Late Carboniferous) is, on the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period (or the upper of two subsystems of the Carboniferous System). It lasted from roughly 323.2 million years ago to 298.9 million years ago. As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by a few hundred thousand years. The Pennsylvanian is named after the U.S. state of Pennsylvania, where the coal beds of this age are widespread.^[5]

The division between Pennsylvanian and Mississippian comes from North American stratigraphy. In North America, where the early Carboniferous beds are primarily marine limestones, the Pennsylvanian was in the past treated as a full-fledged geologic period between the Mississippian and the Permian. In parts of Europe, the Mississippian and Pennsylvanian are one more-or-less continuous sequence of lowland continental deposits and are grouped together as the Carboniferous Period. The current internationally used geologic timescale of the ICS gives the Mississippian and Pennsylvanian the rank of subperiods, subdivisions of the Carboniferous Period.