Cisuralian

The Cisuralian, also known as the Early Permian, is the first series/epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mountains in Russia and Kazakhstan and dates between 298.9 ± 0.15 – 272.3 ± 0.5 Ma.^[4]

Cisuralian
298.9 ± 0.15 – 273.01 ± 0.14 Ma PreꞒ Ꞓ O S D C P T J K Pg N
A map of Earth 285 million years ago during the Cisuralian Epoch, Artinskian Age
Chronology
−300 — – −295 — – −290 — – −285 — – −280 — – −275 — – −270 — – −265 — – −260 — – −255 — – −250 — Paleozoic Mz C Permian Tr Pennsylvanian Cisuralian Guadalup Lopin Early Triassic Asselian Sakmarian Artinskian Kungurian Roadian Wordian Capitanian Wuchiapingian Changhsingian       ← Permian-Triassic mass extinction event ← end-Capitanian extinction event ← Olson's Extinction Subdivision of the Permian according to the ICS, as of 2023.[1] Vertical axis scale: Millions of years ago
Etymology
Name formality	Formal
Synonym(s)	Early/Lower Permian
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Epoch
Stratigraphic unit	Series
Time span formality	Formal
Lower boundary definition	FAD of the conodont Streptognathodus isolatus within the morphotype Streptognathodus wabaunsensis chronocline
Lower boundary GSSP	Aidaralash, Ural Mountains, Kazakhstan 50.2458°N 57.8914°E / 50.2458; 57.8914
Lower GSSP ratified	1996[2]
Upper boundary definition	FAD of the Conodont Jinogondolella nanginkensis
Upper boundary GSSP	Stratotype Canyon, Guadalupe Mountains, Texas, United States 31.8767°N 104.8768°W / 31.8767; -104.8768
Upper GSSP ratified	2001[3]

In the regional stratigraphy of southwestern North America, the Cisuralian encompasses two series: the Wolfcampian (Asselian to mid-Artinskian) and Leonardian (mid-Artinskian to Kungurian).^[5][6][7]

The series saw the appearance of beetles and flies and was a relatively stable warming period of about 21 million years.

Name and background

The Cisuralian is the first series or epoch of the Permian.^[8] The Cisuralian was preceded by the last Pennsylvanian epoch (Gzhelian) and is followed by the Permian Guadalupian Epoch.

The name "Cisuralian" was proposed in 1982,^[9] and approved by the International Subcommission on Permian Stratigraphy in 1996.^[10] The Cisuralian Epoch is named after the western slopes of the Ural Mountains in Russia and Kazakhstan.^[11][12][13]

Limestones on the edge of Russian Platform and make up the Ishimbay oil fields. These oil fields were vital to the Soviet Union during WW2 when the Germans controlled the oil fields to the west.^[11]

The International Chronostratigraphic Chart (v2018/07)^[8] provides a numerical age of 298.9 ± 0.15 – 272.3 ± 0.5 Ma.^[14]

The base of the Cisuralian series and the Permian system is defined as the place in the stratigraphic record where fossils of the conodont Streptognathodus isolatus first appear. The global reference profile for the base (the GSSP or golden spike) is located in the valley of the Aidaralash River, near Aqtöbe in the Ural Mountains of Kazakhstan.^[15]

Geography

The world at the start of the Cisuralian

Gondwana collided with Laurussia and created the Alleghenian orogeny in present-day North America.^[11] In northwestern Europe, the Hercynian orogeny continued.^[11] This created the large supercontinent, Pangea, by the middle of the early Permian, which was to have an impact on the climate.^[11]

Climate

At the start of the Permian, the Late Palaeozoic Ice Age, which began in the Carboniferous, was at its peak. Glaciers receded over the course of the late Cisuralian as the Earth's climate gradually warmed,^[16] particularly during the Artinskian Warming Event,^[17] drying the continent's interiors.^[18][19][20] The pan-tropical belt of Pangaea experienced particularly significant aridification during this epoch.^[21][22][23]

Biodiversity

The swampy fringes were mostly ferns, seed ferns, and lycophytes. The series saw the appearance of beetles and flies.^[11]

The coal swamps from the Carboniferous declined^[24] but the herbivores, Diadectes and Edaphosaurus persisted until the end of this series, approximately.^{[25][26][27][12]} The dry interior had small insectivores. Caseids and prototherapsid Tetraceratops made their appearance.^[12] The marine life was probably more diverse than modern times as the climate warmed.^[11] Unusual sharks such as Helicoprion continued in this series.

Early Permian terrestrial faunas were dominated by pelycosaurs (a paraphyletic group of early synapsids), diadectids, and temnospondyls,^[28][29] The pelycosaurs appeared during the Late Carboniferous, and reached their apex in the Cisuralian remaining the dominant land animals for some 40 million years.^[12][30] A few continued into the Capitanian. They were succeeded by the therapsids.^[12]

• 
  Dimetrodon, a pelycosaur, was at the top of the food chain in the Cisuralian
• 
  Helicoprion bessonovi with characteristic 'tooth-whorl' at front of jaw

Subdivisions

Global

• Asselian stage (298.9 ± 0.15 – 294.6 ± 0.8 Ma)
• Sakmarian stage (294.6 ± 0.8 – 290.1 ± 0.7 Ma)
• Artinskian stage (290.1 ± 0.7 – 283.5 ± 0.7 Ma)
• Kungurian stage (283.5 ± 0.7 – 272.3 ± 0.5 Ma)

Regional

• New Zealand
  • Telfordian (289 – 278 Ma)
  • Mangapirian (278 – 270.6 Ma)