The Gnishik Formation is a geologic formation in Armenia, Azerbaijan and Iran. It preserves fossils dated to the Wordian age of the Permian period.Gnishik Formation in the Paleobiology Database
The thin-bedded limestones of the formation reach a thickness of in the Julfa section of northwestern Iran and in the Arpa River valley of Armenia. The sediments were deposited in an open marine setting at the northern edge of the Paleo-Tethys Ocean.
The coral Wentzellophyllum gnishikense was named after the formation.
Description 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.Leven, 1998, p.302
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, while in Armenia the formation rests on top of the Asni Formation and is overlain by the Arpa Formation.Leven, 1998, p.301 The Gnishik Formation represents an increase in subsidence rate in the Permian.Saidi et al., 1997, p.198 The sediments were deposited at the northern edge of the Paleo-Tethys Ocean.
The formation is dated to the late Murgabian,Leven, 1998, p.308 which belongs to the Wordian stage of the Middle Permian. The Gnishik Formation is correlated with the Ruteh and Nesen Formations,Leven, 1998, p.314 and the Kuffengian stage of Chinese chronostratigraphy.Leven, 1998, p.320
Fossil content Among many others, the following fossils have been reported from the formation:
Invertebrates Trilobites Pseudophillipsia armenica Pseudophillipsia (Carniphillipsia) paffenholzi Acropyge sp. Cephalopods Orthocerida indet.Stepanov et al., 1969 Gastropods Pharkidonotus khairliensis Naticopsis cf. spectatus Bellerophon sp. Naticopsis sp. Straparollus sp. ?Euphemites sp. ?Platyceras sp. Bellerophontidae indet. Corals Ipciphyllum araxense I. flexuosumKotlyar et al., 1989 I. originale I. ex gr. restriseptatum I. simplex I. subtimoricum I. subelegans Lonsdaleia aff. gracilis L. aff. jenningsi Lophocarinophyllum lophophyllidumEzaki, 1991 L. pulchrum L. aff. zaphrentoideum Michelinia vesiculosa Paraipciphyllum transcaucasicum Parawentzelella (Parawentzelella) canalifera Pentaphyllum leptoconicum Praetachylasma alternatum Protomichelinia microstoma Sinopora asiatica Szechuanophyllum szechuanense Ufimia elongata Wentzelella armenica Wentzelella (Wentzelella) densicolumnata Wentzellophyllum gnishikenseKropatcheva, 1999 W. parvus W. volzi Yatsengia asiatica Lophophyllidium sp. Wentzelella sp. Crinoids ?Poteriocrinites ardjichensisStukalina, 1999 Rhynchonellata Cryptospirifer omeishanensisNakamura & Golshani, 1981 Septospirigerella baissalensis Terebratuloidea davidsoniRuzhentsev & Sarycheva Crenispirifer sp. Septospirigerella sp. Strophomenata Chonostegoides baissalensis C. ogbinensis Edriosteges poyangensis Leptodus sp. Stenolaemata Mackinneyella dzhulfensisShishova, 1964Morozova, 1970 Rhabdomeson floriferum Septopora lineata Fusulinina Sichotenella cf. sutschanica Yangchienia cf. haydeni Nankinella cf. ovata N. orbicularia Staffella sphaerica S. suborientalis Eoverbeekina cf. intermedia Pisolina abichi P. subsphaerica Leella ex gr. bellula Sphaerulina crassispira S. ogbinensis Verbeekina cf. heimi V. verbeeki Eopolydiexodina darwasica E. persica Polydiexodina chekiangensis Chusenella abichi C. doraschamensis Dunbarula sp. Foraminifera Globigaetania angulataGennari & Rettori, 2019
Flora Dasycladophyceae Atractyliopsis fecundus Diplopora americana Endoina stellata Epimastopora nipponica Gyroporella tenuimarginata Johnsonia spinosa Macroporella spinosa Mizzia velebitana Pseudogyroporella grandis Pseudovermiporella serbica Stolleyella yabei
Rhodophyceae Succodium ambiguum S. difficile Gymnocodium bellerophonte G. novum Permocalculus forospinus P. fragilis P. piai Ungdarella stellata
See also
List of fossiliferous stratigraphic units in Armenia List of fossiliferous stratigraphic units in Azerbaijan Geology of Armenia Geology of Azerbaijan Geology of Iran
References
Bibliography Geology
Paleontology