Irbzer Formation
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| Irbzer Formation | |
|---|---|
| Stratigraphic range: Maastrichtian-Paleocene ~ | |
| Type | Geological formation |
| Area | Fes-Boulmane |
| Lithology | |
| Primary | Gray mudstone |
| Location | |
| Coordinates | 33°1′N 4°8′W / 33.017°N 4.133°W |
| Approximate paleocoordinates | 24°5′N 5°2′W / 24.083°N 5.033°W |
| Region | Fes-Boulmane |
| Country | Morocco |
  Irbzer Formation (Morocco) | |
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.[1][2]
The Irbzer Formation is 100–440 m thick, that records the transition from marginal-marine to continental environments. It is divided into three members: Lower member (20–190 m): begins with marine-influenced phosphatic sandstones, sandy limestones and marly limestones rich in marine fossils (shark teeth, mosasaurs, bivalves), then passes upward into thick white-to-varicoloured marls, often gypsiferous, with charophytes, ostracods and dinosaur eggshell fragments.[2] Middle member (2–55 m): sharp-based terrigenous interval resting on an erosive disconformity; composed of red sandstones, channelized polymictic conglomerates and siltstones with cross-bedding, ripples and bioturbation, reflecting fluvial-alluvial deposition.[2] Finally, the Upper member (25–170 m): dominantly varicoloured or gray marls with basal gypsum in many sections, thin sandstones and occasional charophyte levels; deposited in restricted lacustrine–floodplain settings.[2]
