Pennsylvanian

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A major division of late Paleozoic time, considered either as an independent period or as the younger subperiod of the Carboniferous. In North America, the Pennsylvanian has been widely recognized as a geologic period and derives its name from a thick succession of mostly nonmarine, coal-bearing strata in Pennsylvania. Radiometric ages place the beginning of the period at approximately 320 million years ago and its end at about 290 million years ago. In northwestern Europe, strata of nearly equivalent age are commonly designated as Upper Carboniferous and in eastern Europe as Middle and Upper Carboniferous. See also Carboniferous.

In North America, the Pennsylvanian Period was characterized by the progressive growth and enlargement of the Alleghenian-Ouachita-Marathon orogenic belt, which formed as the northwestern parts of the large continent Gondwana (mainly northwestern Africa, the area that is now Florida, and northern South America) collided against and deformed the eastern and southern parts of the North American continent. See also Orogeny.

Much of North America remained a stable, low-lying cratonic platform during the Pennsylvanian and was covered by a relatively thin veneer of shallow-water marine carbonates and marine and nonmarine clastic sediments. These were deposited as sea level repeatedly rose and fell as the polar glaciers of southern Gondwana contracted and expanded. In Pennsylvania and along the western part of the present Allegheny Plateau, Pennsylvanian strata are predominantly nonmarine deposits made up of channel sandstones, floodplain shales, siltstones, sandstones, and coals. See also Carbonate minerals; Coal; Craton; Marine sediments.

During Pennsylvanian time, the paleoequator extended across North America from southern California to Newfoundland, through northwestern Europe into the Ukrainian region of eastern Europe, and across parts of northern China. This was a time of extensive coal deposition in a tropical belt that appears to have included areas from 15 to 20° north and south of the paleoequator. Coal of this age is abundant and relatively widespread and has great economic importance.

Petroleum is commonly trapped in nearshore marine deposits of Pennsylvanian age, particularly in carbonate banks near the edge of shelves, in longshore bars and beaches, in reefs and mounds, and at unconformities associated with transgressive-regressive shore lines. Many of these traps contribute significantly to petroleum production. See also Petroleum.

Pennsylvanian paleogeography changed significantly during the period as the supercontinent Pangaea gradually was formed by the joining together of Gondwana and Laurasia. North America and northern Europe, which had been combined into the continent Laurasia since the late Silurian, and South America and northwestern Africa, which formed the northern part of the continent of Gondwana, came together along the Ouachita–Southern Appalachian–Hercynian geosyncline. The result was an extensive orogeny, or mountain-building episode, which supplied the vast amounts of sediments that make up most of the Pennsylvanian strata in the eastern and midwestern parts of the United States. See also Paleogeography.

Evidence in the form of well-developed tree rings, less diverse fossil floras and faunas, and glacial deposits indicates that temperate and glacial conditions were common in nonequatorial climatic belts during Pennsylvanian time. Climatic fluctuations during the period caused significant increases and decreases in the amount of water that was temporarily stored in the glaciers in Gondwana and contributed to eustatic changes of sea level. See also Paleoclimatology.

This article is about the geologic subperiod. For passenger train, see Pennsylvanian (Amtrak).

System	Subsystem/ Series	Stage	Age (Ma)
Permian	Cisuralian	Asselian	younger
Carboniferous	Pennsylvanian	Gzhelian	299.0–303.9
		Kasimovian	303.9–306.5
		Moscovian	306.5–311.7
		Bashkirian	311.7–318.1
	Mississippian	Serpukhovian	318.1–328.3
		Viséan	328.3–345.3
		Tournaisian	345.3–359.2
Devonian	Upper	Famennian	older
Subdivision of the Carboniferous system according to the ICS.[1]

The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous Period. It lasted from roughly 318.1 ± 1.3 to 299 ± 0.8 Ma (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 million years. The Pennsylvanian is named after the American state of Pennsylvania, where rocks with this age are widespread.^[1]

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 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.

Contents 1 Life 1.1 Fungi 1.2 Vertebrates 2 Subdivisions 3 References 4 External links

Life

Generalized geographic map of the United States in middle Pennsylvanian time.

Fungi

All modern classes of fungi were present in the Pennsylvanian.^[2]

Vertebrates

Amphibians were diverse and common; some were several meters long as adults. The collapse of the rainforest ecology in the mid Pennsylvanian (between the Moscovian and the Kasimovian) removed many amphibian species that did not survive as well in the cooler, drier conditions. Reptiles, however, prospered due to specific key adaptations.^[3] One of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed for the further exploitation of the land by certain tetrapods. These included the earliest sauropsid reptiles (Hylonomus), and the earliest known synapsid (Archaeothyris). These small lizard-like animals quickly gave rise to many descendants. Reptiles underwent a major evolutionary radiation, in response to the drier climate that followed the rainforest collapse.^[3][4]

Subdivisions

The Pennsylvanian has been variously subdivided. The international timescale of the ICS follows the Russian subdivision into four stages:

• Bashkirian (oldest)
• Moscovian
• Kasimovian
• Gzhelian (youngest)

North American subdivision is into five stages, but not precisely the same, with additional (older) Appalachian series names following:

• Morrowan stage, corresponding with the middle and lower part of the Pottsville Group (oldest)
• Atokan stage, corresponding with the upper part of the Pottsville group
• Desmoinesian stage, corresponding with the Allegheny Group
• Missourian stage, corresponding with the Conemaugh Group
• Virgilian stage, corresponding with the Monongahela Group (youngest)

The Virgilian or Conemaugh corresponds to the Gzhelian plus the uppermost Kasimovian. The Missourian or Monongahela corresponds to the rest of the Kasimovian. The Desmoinesian or Allegheny corresponds to the upper half of the Moscovian. The Atokan or upper Pottsville corresponds to the lower half of the Moscovian. The Morrowan corresponds to the Bashkirian.

In the European subdivision, the Carboniferous is divided into two epochs: Dinantian (early) and Silesian (late). The Silesian starts earlier than the Pennsylvanian and is divided in three ages:

• Namurian (corresponding to Serpukhovian and early Bashkirian)
• Westphalian (corresponding to late Bashkirian, Moskovian and Kasimovian)
• Stephanian (corresponding to Gzelian).

References

1. ^ ^{a b} Gradstein F, Ogg J (2004). "Geologic Time Scale 2004 – why, how, and where next!" (pdf). Lethaia 37: 175–181. doi:10.1080/00241160410006483. http://www.geo.sc.chula.ac.th/Geology/Thai/News/Geology/pdf/Geological%20Time%20Scale.pdf. Retrieved 2012-03-30. 
2. ^ Blackwell, Meredith, Vilgalys, Rytas, James, Timothy Y., and Taylor, John W. Fungi. Eumycota: mushrooms, sac fungi, yeast, molds, rusts, smuts, etc., February 2008, Tree of Life Web Project
3. ^ ^{a b} Sahney, S., Benton, M.J. & Falcon-Lang, H.J. (2010). "Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica" (pdf). Geology 38 (12): 1079–1082. doi:10.1130/G31182.1. http://geology.geoscienceworld.org/cgi/content/abstract/38/12/1079. 
4. ^ Kazlev MA (1998). "Palaeos Paleozoic: Carboniferous: The Carboniferous Period". http://palaeos.com/paleozoic/carboniferous/carboniferous.htm. Retrieved 2012-03-30. 

External links

• The Late Carboniferous a Time of Great Coal Swamps, Paleomap project. World map from this time period.
• The Carboniferous - 354 to 290 Million Years Ago, University of California Museum of Paleontology. Information on stratigraphies, localities, tectonics, and life.
• The Pennsylvanian Epoch of the Carboniferous Period: 318 to 299 Mya, Paleos.com
• US Geological Survey comparison of time scales

v t e Geologic history of Earth   Precambrian (4.57 Gya – 542 Mya) In left column are eons; right column: bold are eras; not bold are periods: Hadean (4.57 – 4 Gya) (informal) Archean (4 – 2.5 Gya) Eoarchean (4 – 3.6 Gya) Paleoarchean (3.6 – 3.2 Gya) Mesoarchean (3.2 – 2.8 Gya) Neoarchean (2.8 – 2.5 Gya) Proterozoic (2.5 Gya – 542 Mya) Paleoproterozoic (2.5 – 1.6 Gya): Siderian (2.5 – 2.3 Gya) · Rhyacian (2.3 – 2.05 Gya) · Orosirian (2.05 – 1.8 Gya) · Statherian (1.8 – 1.6 Gya) Mesoproterozoic (1.6 – 1 Gya): Calymmian (1.6 – 1.4 Gya) · Ectasian (1.4 – 1.2 Gya) · Stenian (1.2 – 1 Gya) Neoproterozoic (1 Gya – 542 Mya): Tonian (1 Gya – 850 Mya) · Cryogenian (850 – 635 Mya) · Ediacaran (635 – 542 Mya) Mya = millions years ago. Gya = billions years ago.   Phanerozoic (542 – 0 Mya) In horizontal bars are eras; in left column are periods; right column: bold are epochs; not bold not italic are ages; italic are chrons:   Paleozoic (542 – 251 Mya) Cambrian (542 – 488.3 Mya) Terreneuvian (542 – 521 Mya) (de): Fortunian (542 – 528 Mya) (de) · Age 2* (528 – 521 Mya) Epoch 2* (521 – 510 Mya): Age 3* (521 – 515 Mya) · Age 4* (515 – 510 Mya) Epoch 3* (510 – 499 Mya): Age 5* (510 – 506.5 Mya) · Drumian (506.5 – 503 Mya) (de) · Guzhangian (503 – 499 Mya) (de) Furongian (499 – 488.3 Mya): Paibian (499 – 496 Mya) · Jiangshanian (496 – 492 Mya) (de) · Age 10* (492 – 488.3 Mya) Ordovician (488.3 – 443.7 Mya) Early Ordovician (488.3 – 471.8 Mya): Tremadocian (488.3 – 478.6 Mya) · Floian (478.6 – 471.8 Mya) Middle Ordovician (471.8 – 460.9 Mya): Dapingian (471.8 – 468.1 Mya) · Darriwilian (468.1 – 460.9 Mya) Late Ordovician (460.9 – 443.7 Mya): Sandbian (460.9 – 455.8 Mya) · Katian (455.8 – 445.6 Mya) · Hirnantian (445.6 – 443.7 Mya) Silurian (443.7 – 416 Mya) Llandovery (443.7 – 428.2 Mya): Rhuddanian (443.7 – 439 Mya) · Aeronian (439 – 436 Mya) · Telychian (436 – 428.2 Mya) Wenlock (428.2 – 422.9 Mya): Sheinwoodian (428.2 – 426.2 Mya) · Homerian (426.2 – 422.9 Mya) Ludlow (422.9 – 418.7 Mya): Gorstian (422.9 – 421.3 Mya) · Ludfordian (421.3 – 418.7 Mya) Pridoli (418.7 – 416 Mya) Devonian (416 – 359.2 Mya) Early Devonian (416 – 397.5 Mya): Lochkovian (416 – 411.2 Mya) · Pragian (411.2 – 407 Mya) · Emsian (407 – 397.5 Mya) Middle Devonian (397.5 – 385.3 Mya): Eifelian (397.5 – 391.8 Mya) · Givetian (391.8 – 385.3 Mya) Late Devonian (385.3 – 359.2 Mya): Frasnian (385.3 – 374.5 Mya) · Famennian (374.5 – 359.2 Mya) Carboniferous (359.2 – 299 Mya) Mississippian (359.2 – 318.1 Mya): Tournaisian / Early Mississippian (359.2 – 345.3 Mya) · Viséan / Middle Mississippian (345.3 – 328.3 Mya) · Serpukhovian / Late Mississippian (328.3 – 318.1 Mya) Pennsylvanian (318.1 – 299 Mya): Bashkirian / Early Pennsylvanian (318.1 – 311.7 Mya) · Moscovian / Middle Pennsylvanian (311.7 – 307.2 Mya) · Late Pennsylvanian (307.2 – 299 Mya): Kasimovian (307.2 – 303.4 Mya) · Gzhelian (303.4 – 299 Mya) Permian (299 – 251 Mya) Cisuralian (299 – 270.6 Mya): Asselian (299 – 294.6 Mya) · Sakmarian (294.6 – 284.4 Mya) · Artinskian (284.4 – 275.6 Mya) · Kungurian (275.6 – 270.6 Mya) Guadalupian (270.6 – 260.4 Mya): Roadian (270.6 – 268 Mya) · Wordian (268 – 265.8 Mya) · Capitanian (265.8 – 260.4 Mya) Lopingian (260.4 – 251 Mya): Wuchiapingian (260.4 – 253.8 Mya) · Changhsingian (253.8 – 251 Mya)   Mesozoic (251 – 65.5 Mya) Triassic (251 – 199.6 Mya) Early Triassic (251 – 245.9 Mya): Induan (251 – 249.5 Mya) · Olenekian (249.5 – 245.9 Mya) Middle Triassic (245.9 – 228.7 Mya): Anisian (245.9 – 237 Mya) · Ladinian (237 – 228.7 Mya) Late Triassic (228.7 – 199.6 Mya): Carnian (228.7 – 216.5 Mya) · Norian (216.5 – 203.6 Mya) · Rhaetian (203.6 – 199.6 Mya) Jurassic (199.6 – 145.5 Mya) Early Jurassic (199.6 – 175.6 Mya): Hettangian (199.6 – 196.5 Mya) · Sinemurian (196.5 – 189.6 Mya) · Pliensbachian (189.6 – 183 Mya) · Toarcian (183 – 175.6 Mya) Middle Jurassic (175.6 – 161.2 Mya): Aalenian (175.6 – 171.6 Mya) · Bajocian (171.6 – 167.7 Mya) · Bathonian (167.7 – 164.7 Mya) · Callovian (164.7 – 161.2 Mya) Late Jurassic (161.2 – 145.5 Mya): Oxfordian (161.2 – 155.6 Mya) · Kimmeridgian (155.6 – 150.8 Mya) · Tithonian (150.8 – 145.5 Mya) Cretaceous (145.5 – 65.5 Mya) Early Cretaceous (145.5 – 99.6 Mya): Berriasian (145.5 – 140.2 Mya) · Valanginian (140.2 – 133.9 Mya) · Hauterivian (133.9 – 130 Mya) · Barremian (130 – 125 Mya) · Aptian (125 – 112 Mya) · Albian (112 – 99.6 Mya) Late Cretaceous (99.6 – 65.5 Mya): Cenomanian (99.6 – 93.6 Mya) · Turonian (93.6 – 88.6 Mya) · Coniacian (88.6 – 85.8 Mya) · Santonian (85.8 – 83.5 Mya) · Campanian (83.5 – 70.6 Mya) · Maastrichtian (70.6 – 65.5 Mya)   Cenozoic (65.5 – 0 Mya) Paleogene, Neogene and early Pleistocene comprise former Tertiary* (65.5 – 1.8 Mya) period. Gelasian and Calabrian comprise Early Pleistocene (2.588 Mya – 781 kya) subepoch. Paleogene (65.5 – 23.03 Mya) Paleocene (65.5 – 55.8 Mya): Danian (65.5 – 61.1 Mya) · Selandian (61.1 – 58.7 Mya) · Thanetian (58.7 – 55.8 Mya) Eocene (55.8 – 33.9 Mya): Ypresian (55.8 – 48.6 Mya) · Lutetian (48.6 – 40.4 Mya) · Bartonian (40.4 – 37.2 Mya) · Priabonian (37.2 – 33.9 Mya) Oligocene (33.9 – 23.03 Mya): Rupelian (33.9 – 28.4 Mya) · Chattian (28.4 – 23.03 Mya) Neogene (23.03 – 2.588 Mya) Miocene (23.03 – 5.332 Mya): Aquitanian (23.03 – 20.43 Mya) · Burdigalian (20.43 – 15.97 Mya) · Langhian (15.97 – 13.82 Mya) · Serravallian (13.82 – 11.608 Mya)  · Tortonian (11.608 – 7.246 Mya)  · Messinian (7.246 – 5.332 Mya) Pliocene (5.332 – 2.588 Mya): Piacenzian (5.332 – 3.6 Mya) · Zanclean (3.6 – 2.588 Mya) Quaternary (2.588 – 0 Mya) Pleistocene (2.588 Mya – 11.4 kya): Gelasian (2.588 – 1.806 Mya) · Calabrian (1.806 Mya – 781 kya) · Middle Pleistocene / Ionian (781 – 126 kya) · Late Pleistocene / Tarantian (126 – 11.4 kya): Oldest Dryas* (18 – 14.67 kya) · Bølling* (14.67 – 14 kya) · Older Dryas* (14 – 13.7 kya) · Allerød* (13.7 – 12.8 kya) · Younger Dryas* (12.8 – 11.4 kya) Holocene (11.4 – 0 kya): Preboreal* (11.4 – 9 kya) · Boreal* (9 – 8 kya) · Atlantic* (8 – 5 kya) · Subboreal* (5 – 2.5 kya) · Subatlantic* (2.5 – 0 kya) kya = thousands years ago. Mya = millions years ago. * Not officially recognized by the I.C.S. Source: International Stratigraphic Chart. International Commission on Stratigraphy. Retrieved 8 February 2008.

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