View source for Irbzer Formation

{{Infobox rockunit|name=Irbzer Formation|image=|caption=|type=[[Geological formation]]|age=[[Maastrichtian]]-[[Paleocene]] <br/> ~{{fossil range|70|60}}|period=Maastrichtian|prilithology=Gray mudstone|otherlithology=|namedfor=|namedby=|region=[[Fes-Boulmane]]|country=Morocco|coordinates={{coord|33|1|N|4|8|W|region:MA|display=inline,title}}|paleocoordinates={{coord|24|5|N|5|2|W}}|unitof=|subunits=|extent=|area=Fes-Boulmane|map={{Location map+ | Morocco
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  {{ Location map~ | Morocco 
  | lat_deg = 33.0
  | lon_deg = -4.80
  | mark = Green-orange pog.svg
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The '''Irbzer Formation''' is a [[geological formation]] located in [[Morocco]] in the area of [[Fes-Boulmane]] of latest [[Cretaceous]] ([[Maastrichtian]]) to Paleocene 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.<ref name=":0">{{Cite journal |last1=Garcia |first1=G. |last2=Tabuce |first2=R. |last3=Cappetta |first3=H. |last4=Marandat |first4=B. |last5=Bentaleb |first5=I. |last6=Benabdallah |first6=A. |last7=Vianey-Liaud |first7=M. |date=2003 |title=First record of dinosaur eggshells and teeth from the North-West African Maastrichtian (Morocco). |url=https://www.researchgate.net/publication/269703198 |journal=Palaeovertebrata |volume=32 |issue=2–4 |pages=59–69}}</ref> 

== Paleoenvironment ==
[[File:Palaeogeographic models Phosphate basins Morocco - Herbig 1991.png|left|thumb|Reconstructions of the "Phosphate sea" of Morocco. The Irbzer Formation area is seen at the NE ]]
During the [[Maastrichtian]] the inner area was alocated within a Anoxic marine setting, as revelated by bituminous, very oily and dolomitic black shells.<ref>{{Cite journal |last=Jacobshagen |first=Volker H. |date=1988 |title=The Atlas System of Morocco Volume 15 {{!}}{{!}} Synsedimentary tectonics in the Northern Middle Atlas (Morocco) during the late Cretaceous and Tertiary |url=https://link.springer.com/chapter/10.1007/BFb0011599 |journal=Studies on Its Geodynamic Evolution |volume=18 |pages=321–337|doi=10.1007/BFb0011599 }}</ref> Palynology of the underliying and coeval [[El Koubbat Formation]] has revelated an microbiota composed of [[Dinoflagellate|Dinoflagellates]], ''[[Pterospermopsis]]'', [[Scolecodont|Scolecodonts]] and [[Tasmanaceae]].<ref>{{Cite journal |last1=Rauscher |first1=R. |last2=Schuler |first2=M. |last3=Benalioulhaj |first3=N. |date=1986 |title=Les Conditions de Depôt des Schistes Bitumineux et des Phosphates Maastrichtiens au Maroc: une Approche Palynologique. |url=https://paleobotany.ru/palynodata/publication/15643 |journal=Documents du Bureau de Recherches Géologiques et Minières |volume=110 |issue=1 |pages=127–139}}</ref>

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.<ref name=":1">{{Cite journal |last1=Andreu |first1=Bernard |last2=Tronchetti |first2=Guy |date=1996 |title=Ostracodes et foraminifèresdu Crétacé supérieur du synclinal d'El Koubbat, Moyen Atlas, Maroc |url=http://dx.doi.org/10.1016/s0016-6995(96)80071-4 |journal=Geobios |volume=29 |issue=1 |pages=45–71 |doi=10.1016/s0016-6995(96)80071-4 |bibcode=1996Geobi..29...45A |issn=0016-6995}}</ref> 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.<ref name=":1" /> 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.<ref name=":1" /><ref name=":2">{{Cite journal |last1=Colin |first1=Jean-Paul |last2=Tabuce |first2=Rodolphe |date=2004 |title=Ostracodes limniques de la Formation d'Irbzer, Crétacé terminal du Moyen-Atlas, Maroc: taxonomie, biostratigraphie, paléoécologie, paléobiogéographie |url=http://dx.doi.org/10.1016/j.revmic.2004.04.001 |journal=Revue de Micropaléontologie |volume=47 |issue=2 |pages=103–109 |doi=10.1016/j.revmic.2004.04.001 |bibcode=2004RvMic..47..103C |issn=0035-1598}}</ref>

Marine Amniote fauna is know from coeval layers of the [[El Koubbat Formation]], mostly [[Mosasaur|Mosasaurs]] ([[Halisaurinae]], ''[[Gavialimimus]]'', ''[[Globidens]]'', ''[[Mosasaurus]]'', [[Prognathodontini]]) and [[Elasmosauridae]] plesiosaurs.<ref>{{Cite journal |last1=Vinkeles Melchers |first1=Alexander P. M. |last2=Martens |first2=Brennan P. |last3=Rempert |first3=Trevor H. |title=The marine reptile fauna of the Bekrit syncline (El Koubbat Formation, lower Maastrichtian), Middle Atlas Mountains, Morocco |url=https://www.researchgate.net/publication/385855276 |journal=7th Triennial Mosasaur Meeting – A Global Perspective on Mesozoic Marine AmniotesAt: Maastricht, the Netherlands}}</ref>


== Biota ==
{{paleobiota-key-compact}}

=== Charophytes ===
{| class="wikitable"
!Genus
!Species
!Location
!Material
!Notes
!Images
|-
|style="background:#D1FFCF;" |''[[Feistiella]]''<ref name=":3">{{Cite journal |last1=Schudack |first1=Michael |last2=Herbig |first2=H.G. |date=1995 |title=Charophytes from the Cretaceous -Tertiary Boundary Beds of the Middle Atlas Mountains, Morocco |url=http://dx.doi.org/10.3406/geolm.1995.1574 |journal=Géologie Méditerranéenne |volume=22 |issue=3 |pages=125–139 |doi=10.3406/geolm.1995.1574 |issn=0397-2844}}</ref>
|style="background:#D1FFCF;" |
* ''F. sp.''
|style="background:#D1FFCF;" |Oudiksou syncline
|style="background:#D1FFCF;" |Gyrogonites
|style="background:#D1FFCF;" |A charophyte of the family [[Feistiellaceae]]
|style="background:#D1FFCF;" |
|-
|style="background:#D1FFCF;" |''[[Lamprothamnium]]''<ref name=":3" />
|style="background:#D1FFCF;" |
* ''L. sp.''
|style="background:#D1FFCF;" |Oudiksou syncline
|style="background:#D1FFCF;" |Gyrogonites
|style="background:#D1FFCF;" |A charophyte of the family [[Characeae]]
|style="background:#D1FFCF;" |
|-
|style="background:#D1FFCF;" |''[[Sphaerochara]]''<ref name=":3" />
|style="background:#D1FFCF;" |
* ''S. cf. edda''
|style="background:#D1FFCF;" |Oudiksou syncline
|style="background:#D1FFCF;" |Gyrogonites
|style="background:#D1FFCF;" |A charophyte of the family [[Characeae]]
|style="background:#D1FFCF;" |
|-
|style="background:#D1FFCF;" |''[[Stephanochara]]''<ref name=":3" />
|style="background:#D1FFCF;" |
* ''S. sp.''
|style="background:#D1FFCF;" |Oudiksou syncline
|style="background:#D1FFCF;" |Gyrogonites
|style="background:#D1FFCF;" |A charophyte of the family [[Characeae]]
|style="background:#D1FFCF;" |
|}

=== Ostracods ===
{| class="wikitable"
!Genus
!Species
!Location
!Material
!Notes
!Images
|-
|''[[Brachycythere]]''<ref name=":1" />
|
* ''B. cf. gr. sapucariensis''
|El Koubbat
|Valves
|A marine Ostracod of the family [[Brachycytheridae]]
|
|-
|''[[Clithrocytheridea]]''<ref name=":1" />
|
* ''C. senegali'' 
|El Koubbat
|Valves
|A marine Ostracod of the family [[Cytherideidae]]
|
|-
|[[Costa (Ostracod)|''Costa'']]<ref name=":1" />
|
* ''C. sp''
|El Koubbat
|Valves
|A marine Ostracod of the family [[Trachyleberididae]]
|
|-
|''[[Cytheretta]]''<ref name=":1" />
|
* ''C.? koubbatensis''
|El Koubbat
|Valves
|A marine Ostracod of the family [[Cytherettidae]]
|
|-
|''[[Cytherella]]''<ref name=":1" />
|
* ''C. sp''
|El Koubbat
|Valves
|A marine Ostracod of the family [[Cytherellidae]]
|
|-
|''[[Gomphocythere]]''<ref name=":2" />
|
* ''G. achloujensis''
|Achlouj
|Valves
|A freshwater Ostracod of the family [[Limnocytheridae]]
|
|-
|''[[Oertliella]]''<ref name=":1" />
|
* ''O. sp.''
|El Koubbat
|Valves
|A marine Ostracod of the family [[Trachyleberididae]]
|
|-
|''[[Rehacythereis]]''<ref name=":1" />
|
* ''R. sp''
|El Koubbat
|Valves
|A marine Ostracod of the family [[Trachyleberididae]]
|
|-
|''[[Paracandona]]''<ref name=":2" />
|
* ''P. occitanica''
|Achlouj
|Valves
|A freshwater Ostracod of the family [[Candonidae]] 
|
|-
|''[[Paracypris]]''<ref name=":1" />
|
* ''P. cf. mdaouerensis''

* ''P. sp.''
* ''P.? sp.''
|El Koubbat
|Valves
|A marine Ostracod of the family [[Paracyprididae]]
|
|}

=== Echinoderms ===
{| class="wikitable"
!Genus
!Species
!Location
!Material
!Notes
!Images
|-
|''[[Cretasterias]]''<ref>{{Cite journal |last1=GALE |first1=ANDY |last2=VILLIER |first2=LOÏC |date=2013 |title=Mass mortality of an asteriid starfish (Forcipulatida, Asteroidea, Echinodermata) from the late Maastrichtian (Late Cretaceous) of Morocco |url=http://dx.doi.org/10.1111/pala.12002 |journal=Palaeontology |volume=56 |issue=3 |pages=577–588 |doi=10.1111/pala.12002 |bibcode=2013Palgy..56..577G |issn=0031-0239}}</ref>
|
* ''C. reticulatus'' 
|Bakrit
|Thousands of specimens
|A sea star of the family [[Asteriidae]]
|
|}

=== Fish ===
{| class="wikitable"
!Genus
!Species
!Location
!Material
!Notes
!Images
|-
|''[[Cretalamna]]''<ref name=":0" />
|
* ''C. maroccana''
|Oukdiksou syncline
|Teeth
|A Shark of the family [[Otodontidae]]
|[[File:Cretalamna reconstruction.png|thumb|''Cretalmana'' reconstruction]]
|-
|''[[Dalpiazia]]''<ref name=":0" />
|
* ''D. strollleri''
|Oukdiksou syncline
|Teeth
|A [[Chondrichthyes|Chondrichthian]] of the family [[Sclerorhynchidae]]
|
|-
|''[[Ganopristis]]''<ref name=":0" />
|
* ''G. leptodoll'' 
|Oukdiksou syncline
|Teeth
|A [[Chondrichthyes|Chondrichthian]] of the family [[Sclerorhynchidae]]
|
|-
|''[[Serratolamna]]''<ref name=":0" />
|
* ''S. serrata''
|Oukdiksou syncline
|Teeth
|A Shark of the family [[Serratolamnidae]]
|
|-
|''[[Squalicorax]]''<ref name=":0" />
|
* ''S. pristodontus''
* ''S. bassallii'' 
|Oukdiksou syncline
|Teeth
|A Shark of the family [[Anacoracidae]]
|[[File:Squalicorax2DB.jpg|thumb|''[[Squalicorax]]'' reconstruction]]
|}

=== Crocodrylomorpha ===
{| class="wikitable"
!Genus
!Species
!Location
!Material
!Notes
!Images
|-
|style="background:#E3F5FF;"|[[Krokolithidae]]<ref name=":0" />
|style="background:#E3F5FF;"|
* Indeterminate
|style="background:#E3F5FF;"|Oukdiksou syncline
|style="background:#E3F5FF;"|eggshells
|style="background:#E3F5FF;"|Indeterminate Crocodrilian eggshells
|style="background:#E3F5FF;"|
|}

=== Sauropoda ===
{| class="wikitable"
!Genus
!Species
!Location
!Material
!Notes
!Images
|-
|style="background:#E3F5FF;"|''[[Pseudomegaloolithus]]''<ref name=":0" />
|style="background:#E3F5FF;"|
* ''P. atlasi''
|style="background:#E3F5FF;"|Oukdiksou syncline
|style="background:#E3F5FF;"|eggshells
|style="background:#E3F5FF;"|Indeterminate Sauropod eggshells
|style="background:#E3F5FF;"|
|-
|style="background:#E3F5FF;"|''[[Megaloolithus]]''<ref name=":0" />
|style="background:#E3F5FF;"|
* ''M. maghrebiensis'' 
* ''M. sp.'' 
|style="background:#E3F5FF;"|Oukdiksou syncline
|style="background:#E3F5FF;"|eggshells
|style="background:#E3F5FF;"|Eggshells referred to [[Titanosauridae]] sauropods
|style="background:#E3F5FF;"|[[File:Underside of a clutch of Megaloolithus siruguei at Pinyes locality - Tremp Formation.jpg|thumb|Example of ''[[Megaloolithus]]'' ]]
|}

=== Theropoda ===
{| class="wikitable"
!Genus
!Species
!Location
!Material
!Notes
!Images
|-
|style="background:#E3F5FF;"|''[[Pseudogeckoolithus]]''<ref name=":0" />
|style="background:#E3F5FF;"|
* ''P. tirboulensis''
|style="background:#E3F5FF;"|Oukdiksou syncline
|style="background:#E3F5FF;"|eggshells
|style="background:#E3F5FF;"|Theropod eggs referred to [[Maniraptora]]
|style="background:#E3F5FF;"|
|-
|style="background:#E3F5FF;"|''[[Rodolphoolithus]]''<ref name=":0" />
|style="background:#E3F5FF;"|
* ''R. arioul''
|style="background:#E3F5FF;"|Oukdiksou syncline
|style="background:#E3F5FF;"|eggshells
|style="background:#E3F5FF;"|Indeterminate eggs likely laid by small theropods
|style="background:#E3F5FF;"|
|-
|"''[[Paronychodon]]''"<ref name=":0" />
|
* ''"P. sp."''
|Oukdiksou syncline
|Teeth
|A theropod, probably related with [[Troodontidae]] or [[Unenlagiinae]]
|
|-
|style="background:#E3F5FF;"|''[[Tipoolithus]]''<ref name=":0" />
|style="background:#E3F5FF;"|
* ''T. achloujensis'' 
|style="background:#E3F5FF;"|Oukdiksou syncline
|style="background:#E3F5FF;"|eggshells
|style="background:#E3F5FF;"|Theropod eggs, referred to an [[enantiornithine]] [[bird]] or small [[theropod]]
|style="background:#E3F5FF;"|
|}

== References ==
{{Reflist}}

{{Major African geological formations}}

[[Category:Geology of Morocco]]
[[Category:Cretaceous paleontological sites of Africa]]
[[Category:Cretaceous System of Africa]]
[[Category:Paleontological sites of Morocco]]