The Middle - Upper Jurassic carbonates in north - west of Maragheh consist of dark coloured fossiliferous limestones (Dalichai Fm.) & Light coloured limestones & dolomites (Lar Fm.) with a total thickness of 483 m.
Facies analysis indicate that, the Dalichai carbonates were formed in an open marine environment & the Lar carbonates were deposited in a bar - lagoon & tidal flat environments.
Recognized microfacies in the Dalichai Formation consist of fossiliferrous mudstones, Radiolaria wackestone and Posidonia wackestones.Identified microfacies in the Lar Formation consist of wackestone to packstone rudstone, Forameniferal wackestone and peloidal grainstones.
Since, differentation between Dalichai and Lar Formations in the study area, are often difficult, due to petrographic similarities, trace element variations (Sr, Na, Mn, Sr/Na) and oxygen and carbon isotope values were used to discriminate between Dalichai and Lar Formations.