Irhazer Gr
Period:
Jurassic
Age Interval:
Mid-to-Late Jurassic (1)
Province:
Iullemmeden Basin - Tim Mersoï Sub-basin
Type Locality and Naming
Irhazer Fm (shales) at the base and the Tiouraren Fm at the top. Includes Upper part of the Dabla Subgroup
References: Moody and Sutcliffe, 1991; Rauhut & López-Arbarello, 2009; Mudroch et al., 2011.
Synonym: Argiles de l’Irhazer
Lithology and Thickness
Composed of the Irhazer Fm (shales) at the base and the Tiouraren Fm (soil cycles) at the top. (See these formations for more details). Thickness is 380 m around In Gall
Lithology Pattern:
Sandy claystone
Relationships and Distribution
Lower contact
Overlies the Agadez Gr (Assaouas Fm when present, or the Tchirezrine 2 Mbr of the Tchirezrine Fm).
Upper contact
Overlain by the Tégama Gr
Regional extent
GeoJSON
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Age
Mid-to-Late Jurassic. According to Moody and Sutcliffe (1991), no ages are available for the units of the Irhazer Group below the Tiouraren Formation due to the lack of suitable fossils, although these authors assumed a Late Jurassic–Early Cretaceous age for this unit. Mudroch et al. (2011) determined a Mid-Jurassic age (see “Irhazer Fm”).
Age Span:
Beginning stage:
Bathonian
Fraction up in beginning stage:
0.0
Beginning date (Ma):
168.17
Ending stage:
Tithonian
Fraction up in the ending stage:
1.0
Ending date (Ma):
143.10
Depositional setting
Continental fluvio-lacustrine
Depositional pattern:
Additional Information
Compiler:
Jacques LeBlanc (2022), Stratigraphic Lexicon: The Sedimentary Formations of The Republic of Niger, Africa. Colnes Publishing (Tallin, Estonia), 365 pp. https://doi.org/10.47909/978-9916-9760-6-7 (or via https://sites.google.com/site/leblancjacques)