Anisian

In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 246.7 million years ago until 241.464 million years ago.^[7] The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic Epoch) and precedes the Ladinian Age.

Anisian
246.7 – 241.464 ± 0.28 Ma PreꞒ Ꞓ O S D C P T J K Pg N
The Muschelkalk in Europe is mainly Anisian aged
Chronology
−255 — – −250 — – −245 — – −240 — – −235 — – −230 — – −225 — – −220 — – −215 — – −210 — – −205 — – −200 — Pz Mesozoic P Triassic J LP ET Middle Late E J Changhsing. Olenekian Induan Anisian Ladinian Carnian Norian Rhaetian Hettangian         ← Permian-Triassic extinction event ← Smithian–Spathian boundary event[1] ← Carnian pluvial episode ← Full recovery of woody trees[2] ← Coals return[3] ← Scleractinian corals & calcified sponges[4] ← Triassic–Jurassic extinction event ← Manicouagan impact Subdivision of the Triassic according to the ICS, as of 2024.[5] 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	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	Not formally defined
Lower boundary definition candidates	FAD of the Conodont Chiosella timorensis Base of magnetic zone MT1n
Lower boundary GSSP candidate section(s)	Desli Caira, Northern Dobruja, Romania Guandao, Guizhou, China
Upper boundary definition	FAD of the Ammonite Eoprotrachyceras curionii
Upper boundary GSSP	Bagolino, Lombardian pre-Alps, Italy 45.8193°N 10.4710°E / 45.8193; 10.4710
Upper GSSP ratified	2005[6]

Stratigraphic definitions

The stage and its name were established by Austrian geologists Wilhelm Heinrich Waagen and Carl Diener in 1895. The name comes from Anisus, the Latin name of the river Enns. The original type locality is at Großreifling in the Austrian state of Styria.

The base of the Anisian Stage (also the base of the Middle Triassic series) is sometimes laid at the first appearance of conodont species Chiosella timorensis in the stratigraphic record. Other stratigraphers prefer to use the base of magnetic chronozone MT1n. There is no accepted global reference profile for the base, but one (GSSP or golden spike) was proposed at a flank of the mountain Deșli Caira in the Romanian Dobruja.^[8]

The top of the Anisian (the base of the Ladinian) is at the first appearance of ammonite species Eoprotrachyceras curionii and the ammonite family Trachyceratidae. The conodont species Neogondolella praehungarica appears at the same level.

Especially in Central Europe the Anisian Stage is sometimes subdivided into four substages: Aegean, Bythinian, Pelsonian and Illyrian.

The Anisian contains six ammonite biozones:

• zone of Nevadites
• zone of Hungarites
• zone of Paraceratites
• zone of Balatonites balatonicus
• zone of Kocaelia
• zone of Acrochordiceras

Selected formations

• Ashfield Shale (New South Wales, Australia)
• Lower and middle Besano Formation (Switzerland and Italy)
• Upper Ermaying Formation (Shaanxi and Shanxi, China)
• Favret Formation / Prida Formation (Fossil Hill Member) (Nevada, US)
• Grès à Voltzia (France)
• Guanling Formation (Guizhou and Yunnan, China)
• Moenkopi Formation (Holbrook and Anton Chico members) (SW US)
• Lower and Middle Muschelkalk (central Europe)
• Röt Formation / Upper Buntsandstein (Germany)