The Gnishik Formation was first formally described by Arakelyan in 1964, based on a section in the
Gnishik River valley, after which the formation was named. The formation is mostly represented by thin-bedded, occasionally shaly, dark grey and black
bituminous foraminiferal-algal biodetrital
limestones. The occasional admixture of clayey and terrigenous material colors the limestones light grey and yellowish. The thin-bedded layers alternate with coarser-bedded compact varieties. The open marine
limestones of the formation reach a thickness of in the Julfa section of northwestern Iran. In Iran, the formation overlies the
Dorud Formation and is overlain by the
Khachik Formation, The Gnishik Formation represents an increase in
subsidence rate in the Permian. The sediments were deposited at the northern edge of the
Paleo-Tethys Ocean. The formation is dated to the late
Murgabian, which belongs to the
Wordian stage of the
Middle Permian. and the
Kuffengian stage of Chinese chronostratigraphy. == Fossil content ==