Aganane Formation

The Aganane Formation (also known as Aït Chitachen, Aït Bazzi or Assemsouk Formation in the High Atlas and Calcaires de Tizi Nehassa in the Middle Atlas) is a Pliensbachian (Early Jurassic), with some levels being potentially Latest Sinemurian, geologic formation in the Khenifra, Midelt, Azilal, Béni-Mellal, Ouarzazate, Tinerhir and Errachidia areas, in the Middle and High Atlas of Morocco, being the remnant of a local massive Carbonate platform, and known mostly for its rich tracksites (up to 1350 tracks in 1988) including footprints of dinosaurs. It may also include the fossiliferous levels of the Calcaires du Bou Dahar, if true, it would be one of the richest Early Jurassic formations in the entire tethys area.

This formation has been dated to the Pliensbachian stage of the Lower Jurassic, thanks to the find of the ammonite Arieticeras cf. algovianum, indicator of Middle Domerian (=Uppermost Pliensbachian) in the upper zone, and lower delimitation by the foraminifers Mayncina termieri and Orbitopsella praecursor (indicators of Carixian=Lower Pliensbachian age). The dinosaur tracksites are all located a few metres below the Pliensbachian-Toarcian limit, being coeval and connected with the lowermost layers of the continental Azilal Formation. The Aganane Formation was also coeval with the Jbel Taguendouft Formation, all developed along a local "platform-furrow" in the Middle Atlas Mountains, that act as a barrier controlling the western border of the Jurassic Atlas Gulf. The nearshore sections, including both carbonate platforms and close to sea terrestrial facies where located on an isolated internal domain thanks to the control of the barrier, allowing the Aganane Formation to develop on a hot and humid climate, where a local algal marsh had intermittent progradations, intercalated with a layer of terrigenous continental origin. The ichnosites were developed in tidal flats and coastal deposits suitable to sea flooding.

The Aganane Formation is a member of the Pliensbachian facies section of the Central Atlas, which are distributed from west to east: The sequences referred to either the synonyms "Aït Chitachen" & "Aït Bazzi" Formations at W sectors such as Demnate or Telouet (continental-fluvial, coastal lagoon) and the Aganane itself at the Azilal area, where the village of the same name is found. At Tazoult, part of the Azilal profile contacts the bottom with the karst Talmest-Tazoult Formation, then a section where the Aganane itself indicates an eastward expansion of the carbonate facies, finally, a westward advance of the Imilchil pelagic facies, mostly part of the Jbel Choucht Formation or Ouchbis Formation.