Bajocian

In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ±0.8 Ma to around 168.2 ±1.2 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age.^[4]

Bajocian
170.9 ± 0.8 – 168.2 ± 1.2 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Chronology
−205 — – −200 — – −195 — – −190 — – −185 — – −180 — – −175 — – −170 — – −165 — – −160 — – −155 — – −150 — – −145 — – −140 — Mesozoic T Jurassic K LT Early Middle Late EK Rhaetian Hettangian Sinemurian Pliensbachian Toarcian Aalenian Bajocian Bathonian Callovian Oxfordian Kimmeridgian Tithonian Berriasian       ← Triassic–Jurassic extinction event Subdivision of the Jurassic according to the ICS, as of 2024.[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	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	FAD of the Ammonites Hyperlioceras mundum, Hyperlioceras furcatum, Braunsina aspera, and Braunsina elegantula
Lower boundary GSSP	Cabo Mondego, Portugal 40.1992°N 8.9042°W / 40.1992; -8.9042
Lower GSSP ratified	1996[2]
Upper boundary definition	FAD of the Ammonite Gonolkites convergen
Upper boundary GSSP	Ravin du Bès, Bas-Auran, Alpes de Haute, France 43.9606°N 6.3153°E / 43.9606; 6.3153
Upper GSSP ratified	July 2008[3]

Stratigraphic definitions

The Bajocian Stage takes its name from the Latin name (Bajocae) of the town of Bayeux, in the region of Normandy in France. The stage was named and introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1842.

The base of the Bajocian stage is defined as the place in the stratigraphic column where fossils of the ammonite genus Hyperlioceras first appear. A global reference profile (a GSSP) for the base is located at Murtinheira, close to Cabo Mondego in Portugal.^[5] The top of the Bajocian (the base of the Bathonian) is at the first appearance of ammonite species Parkinsonia convergens.

Subdivision

The Bajocian is often divided into Lower/Early and Upper/Late subages or substages.

In the Tethys domain, the Bajocian contains seven ammonite biozones:

• zone of Parkinsonia parkinsoni
• zone of Garantiana garantiana
• zone of Strenoceras niortense
• zone of Stephanoceras humphriesianum
• zone of Sonninia propinquans
• zone of Witchellia laeviuscula
• zone of Hyperlioceras discites