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Irbzer Formation

Coordinates: 33°1′N 4°8′W / 33.017°N 4.133°W / 33.017; -4.133
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Irbzer Formation
Stratigraphic range: Maastrichtian
~70–66 Ma
TypeGeological formation
AreaFes-Boulmane
Lithology
PrimaryGray mudstone
Location
Coordinates33°1′N 4°8′W / 33.017°N 4.133°W / 33.017; -4.133
Approximate paleocoordinates24°5′N 5°2′W / 24.083°N 5.033°W / 24.083; -5.033
RegionFes-Boulmane
CountryMorocco
Irbzer Formation is located in Morocco
Irbzer Formation
Irbzer Formation (Morocco)

The Irbzer Formation is a geological formation located in Morocco in the area of Fes-Boulmane of latest Cretaceous (Maastrichtian) age. The lower section of this formation consists of yellowish, cross-bedded calcareous sandstone containing shark teeth, while the layer above comprises phosphatic marls with vertebrate bone beds, including dinosaur remains.[1]

Paleoenvironment

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The formation reflects a shallow marine to lagoonal setting, transitioning from fine sands to marls and limestones. The presence of marine organisms, including bivalves and gastropods, along with phosphatic layers containing fish remains, indicates periodic marine incursions, with intermittent lagoonal or nearshore conditions.[2] Oxidation and sedimentary discontinuities suggest episodes of exposure or subaerial erosion. The overall environment was likely a shallow, low-energy, marginal marine setting with occasional deeper marine influences.[2] No planktonic foraminifera are present, and the few benthic foraminifera offer limited ecological insights. However, ostracodes, though poorly preserved, are more abundant and provide significant information about the environment. The ostracode assemblage including indicates a shallow (0–20 m), oligohaline, moderately alkaline, and relatively warm limnic environment, likely permanent and near the shoreline, as suggested by the presence of isolated dinosaur teeth and eggshell fragments in these layers.[2][3]

Biota

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Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Charophytes

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Genus Species Location Material Notes Images
Feistiella[4]
  • F. sp.
Oudiksou syncline Gyrogonites A charophyte of the family Feistiellaceae
Lamprothamnium[4]
  • L. sp.
Oudiksou syncline Gyrogonites A charophyte of the family Characeae
Sphaerochara[4]
  • S. cf. edda
Oudiksou syncline Gyrogonites A charophyte of the family Characeae
Stephanochara[4]
  • S. sp.
Oudiksou syncline Gyrogonites A charophyte of the family Characeae

Ostracods

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Genus Species Location Material Notes Images
Brachycythere[2]
  • B. cf. gr. sapucariensis
El Koubbat Valves A marine Ostracod of the family Brachycytheridae
Clithrocytheridea[2]
  • C. senegali
El Koubbat Valves A marine Ostracod of the family Cytherideidae
Costa[2]
  • C. sp
El Koubbat Valves A marine Ostracod of the family Trachyleberididae
Cytheretta[2]
  • C.? koubbatensis
El Koubbat Valves A marine Ostracod of the family Cytherettidae
Cytherella[2]
  • C. sp
El Koubbat Valves A marine Ostracod of the family Cytherellidae
Gomphocythere[3]
  • G. achloujensis
Achlouj Valves A freshwater Ostracod of the family Limnocytheridae
Oertliella[2]
  • O. sp.
El Koubbat Valves A marine Ostracod of the family Trachyleberididae
Rehacythereis[2]
  • R. sp
El Koubbat Valves A marine Ostracod of the family Trachyleberididae
Paracandona[3]
  • P. occitanica
Achlouj Valves A freshwater Ostracod of the family Candonidae
Paracypris[2]
  • P. cf. mdaouerensis
  • P. sp.
  • P.? sp.
El Koubbat Valves A marine Ostracod of the family Paracyprididae

Echinoderms

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Genus Species Location Material Notes Images
Cretasterias[5]
  • C. reticulatus
Bakrit Thousands of specimens A sea star of the family Asteriidae

Fish

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Genus Species Location Material Notes Images
Cretalamna[1]
  • C. maroccana
Oukdiksou syncline Teeth A Shark of the family Otodontidae
Cretalmana reconstruction
Dalpiazia[1]
  • D. strollleri
Oukdiksou syncline Teeth A Chondrichthian of the family Sclerorhynchidae
Ganopristis[1]
  • G. leptodoll
Oukdiksou syncline Teeth A Chondrichthian of the family Sclerorhynchidae
Serratolamna[1]
  • S. serrata
Oukdiksou syncline Teeth A Shark of the family Serratolamnidae
Squalicorax[1]
  • S. pristodontus
  • S. bassallii
Oukdiksou syncline Teeth A Shark of the family Anacoracidae
Squalicorax reconstruction

Crocodrylomorpha

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Genus Species Location Material Notes Images
Krokolithidae[1]
  • Indeterminate
Oukdiksou syncline eggshells Indeterminate Crocodrilian eggshells

Sauropoda

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Genus Species Location Material Notes Images
Pseudomegaloolithus[1]
  • P. atlasi
Oukdiksou syncline eggshells Indeterminate Sauropod eggshells
Megaloolithus[1]
  • M. maghrebiensis
  • M. sp.
Oukdiksou syncline eggshells Eggshells referred to Titanosauridae sauropods
Example of Megaloolithus

Theropoda

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Genus Species Location Material Notes Images
Pseudogeckoolithus[1]
  • P. tirboulensis
Oukdiksou syncline eggshells Theropod eggs referred to Maniraptora
Rodolphoolithus[1]
  • R. arioul
Oukdiksou syncline eggshells Indeterminate eggs likely laid by small theropods
"Paronychodon"[1]
  • "P. sp."
Oukdiksou syncline Teeth A theropod, probably related with Troodontidae or Unenlagiinae
Tipoolithus[1]
  • T. achloujensis
Oukdiksou syncline eggshells Theropod eggs, referred to an enantiornithine bird or small theropod

References

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  1. ^ a b c d e f g h i j k l m Garcia, G.; Tabuce, R.; Cappetta, H.; Marandat, B.; Bentaleb, I.; Benabdallah, A.; Vianey-Liaud, M. (2003). "First record of dinosaur eggshells and teeth from the North-West African Maastrichtian (Morocco)" (PDF). Palaeovertebrata. 32 (2–4): 59–69.
  2. ^ a b c d e f g h i j k Andreu, Bernard; Tronchetti, Guy (1996). "Ostracodes et foraminifèresdu Crétacé supérieur du synclinal d'El Koubbat, Moyen Atlas, Maroc". Geobios. 29 (1): 45–71. doi:10.1016/s0016-6995(96)80071-4. ISSN 0016-6995.
  3. ^ a b c Colin, Jean-Paul; Tabuce, Rodolphe (2004). "Ostracodes limniques de la Formation d'Irbzer, Crétacé terminal du Moyen-Atlas, Maroc: taxonomie, biostratigraphie, paléoécologie, paléobiogéographie". Revue de Micropaléontologie. 47 (2): 103–109. doi:10.1016/j.revmic.2004.04.001. ISSN 0035-1598.
  4. ^ a b c d Schudack, Michael; Herbig, H.G. (1995). "Charophytes from the Cretaceous -Tertiary Boundary Beds of the Middle Atlas Mountains, Morroco". Géologie Méditerranéenne. 22 (3): 125–139. doi:10.3406/geolm.1995.1574. ISSN 0397-2844.
  5. ^ GALE, ANDY; VILLIER, LOÏC (2013). "Mass mortality of an asteriid starfish (Forcipulatida, Asteroidea, Echinodermata) from the late Maastrichtian (Late Cretaceous) of Morocco". Palaeontology. 56 (3): 577–588. doi:10.1111/pala.12002. ISSN 0031-0239.