Gnishik Formation

Gnishik Formation
Stratigraphic range: Wordian (late Murgabian) ~268–265 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Formation
Underlies	Arpa Formation (Armenia) Khachik Formations (Iran)
Overlies	Asni Formation (Armenia) Dorud Formation (Iran)
Thickness	300 m (980 ft) (Armenia) 670 m (2,200 ft) (Iran)
Lithology
Primary	Limestone
Other	Shale
Location
Coordinates	39.0°N 45.0°E / 39.0; 45.0
Approximate paleocoordinates	9.1°S 41.4°E / -9.1; 41.4
Region	Transcaucasia
Country	Armenia Azerbaijan Iran
Extent	Alborz Mountains
Type section
Named for	Gnishik River
Named by	Arakelyan
Year defined	1964
Gnishik Formation (Caucasus Mountains)

The Gnishik Formation is a geologic formation in Armenia, Azerbaijan and Iran. It preserves fossils dated to the Wordian age of the Permian period.[1]

The thin-bedded limestones of the formation reach a thickness of 670 metres (2,200 ft) in the Julfa section of northwestern Iran and 300 metres (980 ft) 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.[2]

The open marine limestones of the formation reach a thickness of 670 metres (2,200 ft) in the Julfa section of northwestern Iran. In Iran, the formation overlies the Dorud Formation and is overlain by the Khachik Formation,[3] while in Armenia the formation rests on top of the Asni Formation and is overlain by the Arpa Formation.[4] The Gnishik Formation represents an increase in subsidence rate in the Permian.[3] The sediments were deposited at the northern edge of the Paleo-Tethys Ocean.

The formation is dated to the late Murgabian,[5] which belongs to the Wordian stage of the Middle Permian.[1] The Gnishik Formation is correlated with the Ruteh and Nesen Formations,[6] and the Kuffengian stage of Chinese chronostratigraphy.[7]

Fossil content

Among many others, the following fossils have been reported from the formation:[1]

Invertebrates

Trilobites

• Pseudophillipsia armenica[8]
• Pseudophillipsia (Carniphillipsia) paffenholzi[8][9]
• Acropyge sp.[8]

Cephalopods

• Orthocerida indet.[9]

Gastropods

• Pharkidonotus khairliensis[9]
• Naticopsis cf. spectatus[9]
• Bellerophon sp.[9]
• Naticopsis sp.[9]
• Straparollus sp.[9]
• ?Euphemites sp.[9]
• ?Platyceras sp.[9]
• Bellerophontidae indet.[9]

Corals

• Ipciphyllum araxense[10]
• I. flexuosum[11]
• I. originale[11]
• I. ex gr. restriseptatum[11]
• I. simplex[11]
• I. subtimoricum[11][12]
• I. subelegans[11]
• Lonsdaleia aff. gracilis[12]
• L. aff. jenningsi[12]
• Lophocarinophyllum lophophyllidum[13]
• L. pulchrum[10][11]
• L. aff. zaphrentoideum[12]
• Michelinia vesiculosa[8]
• Paraipciphyllum transcaucasicum[11]
• Parawentzelella (Parawentzelella) canalifera[12]
• Pentaphyllum leptoconicum[13]
• Praetachylasma alternatum[12]
• Protomichelinia microstoma[13]
• Sinopora asiatica[13]
• Szechuanophyllum szechuanense[12]
• Ufimia elongata[8]
• Wentzelella armenica[12]
• Wentzelella (Wentzelella) densicolumnata[8]
• Wentzellophyllum gnishikense[10]
• W. parvus[10]
• W. volzi[12]
• Yatsengia asiatica[12]
• Lophophyllidium sp.[11]
• Wentzelella sp.[11]

Crinoids

• ?Poteriocrinites ardjichensis[14]

Rhynchonellata

• Cryptospirifer omeishanensis[15]
• Septospirigerella baissalensis[15]
• Terebratuloidea davidsoni[8]
• Crenispirifer sp.[15]
• Septospirigerella sp.[15]

Strophomenata

• Chonostegoides baissalensis[15]
• C. ogbinensis[8]
• Edriosteges poyangensis[8]
• Leptodus sp.[15]

Stenolaemata

• Mackinneyella dzhulfensis[8][16][12]
• Rhabdomeson floriferum[16]
• Septopora lineata[16]

Fusulinina

• Sichotenella cf. sutschanica[8]
• Yangchienia cf. haydeni[8]
• Nankinella cf. ovata[8]
• N. orbicularia[8]
• Staffella sphaerica[8]
• S. suborientalis[8]
• Eoverbeekina cf. intermedia[8]
• Pisolina abichi[8]
• P. subsphaerica[8]
• Leella ex gr. bellula[8]
• Sphaerulina crassispira[8]
• S. ogbinensis[8]
• Verbeekina cf. heimi[8]
• V. verbeeki[8]
• Eopolydiexodina darwasica[8]
• E. persica[8]
• Polydiexodina chekiangensis[8]
• Chusenella abichi[8]
• C. doraschamensis[8]
• Dunbarula sp.[8]

Foraminifera

• Globigaetania angulata[17]

Flora

Dasycladophyceae

• Atractyliopsis fecundus[8]
• Diplopora americana[8]
• Endoina stellata[8]
• Epimastopora nipponica[8]
• Gyroporella tenuimarginata[8]
• Johnsonia spinosa[8]
• Macroporella spinosa[8]
• Mizzia velebitana[8]
• Pseudogyroporella grandis[8]
• Pseudovermiporella serbica[8]
• Stolleyella yabei[8]

Rhodophyceae

• Succodium ambiguum[8]
• S. difficile[8]
• Gymnocodium bellerophonte[8]
• G. novum[8]
• Permocalculus forospinus[8]
• P. fragilis[8]
• P. piai[8]
• Ungdarella stellata[8]

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

1. Gnishik Formation in the Paleobiology Database
2. Leven, 1998, p.302
3. Saidi et al., 1997, p.198
4. Leven, 1998, p.301
5. Leven, 1998, p.308
6. Leven, 1998, p.314
7. Leven, 1998, p.320
8. Ruzhentsev & Sarycheva
9. Stepanov et al., 1969
10. Kropatcheva, 1999
11. Kotlyar et al., 1989
12. Morozova, 1970
13. Ezaki, 1991
14. Stukalina, 1999
15. Nakamura & Golshani, 1981
16. Shishova, 1964
17. Gennari & Rettori, 2019

Bibliography

Geology

• Leven, Ernst J.A (1998), "Permian fusulinid assemblages and stratigraphy of the Transcaucasia", Rivista Italiana di Paleontologia e Stratigrafia, 104 (3): 299–328, retrieved 2020-08-01
• Saidi, Abdollah; Brunet, Marie-Françoise; Ricou, Luc-Emmanuel (1997), "Continental accretion of the Iran Block to Eurasia as seen from Late Paleozoic to Early Cretaceous subsidence curves", Geodinamica Acta, 10 (5): 189–208, doi:10.1080/09853111.199 (inactive 1 November 2024)

Paleontology

• Gennari, Valerio; Rettori, Roberto (2019), "Globigaetania angulata gen. n. sp. n. (Globivalvulininae, Foraminifera) from the Wordian (Middle Permian) of NW Iran", Rivista Italiana di Paleontologia e Stratigrafia, 125 (1): 1–11, doi:10.13130/2039-4942/11054
• Kropatcheva, G. S (1999), "Novie vidi pozdnepermski rugoz zakavkaziya - New materials of Late Permian rugosans from the Caucasus", Voprosy Paleontologii, 11: 24–32
• Stukalina, G. A (1999), "The Late Permian crinoids from Primorye, Transcaucasia, and North Caucasus", Paleontological Journal, 33: 139–146
• Ezaki, Y (1991), "Permian corals from Abadeh and Julfa, Iran, West Tethys", Journal of the Faculty of Science, Hokkaido University, Series IV, 23: 53–146
• Kotlyar, G. V.; Zakharov, Y.u. D.; Kropatcheva, G. S.; Pronina, G. P.; Chedija, I. O.; Burago, V. I. (1989), Evolution of the latest Permian biota: Midian regional stage in the USSR, ., pp. 1–184
• Nakamura, K.; Golshani, F. (1981), "Notes on the Permian brachiopod genus Cryptospirifer", Journal of the Faculty of Science, Hokkaido University, Series 4, Geology and Mineralogy, 20: 67–77
• Morozova, I. P (1970), "Mshanki Pozdnei Permi", Akademiya Nauk SSSR, Trudy Paleontologicheskogo Instituta, 122: 1–346
• Stepanov, D. L.; Golshani, F.; Stöcklin, J. (1969), "Upper Permian and Permian-Triassic boundary in north Iran", Geological Survey of Iran Report, 12: 1–72
• Ruzhentsev, V. E.; Sarycheva, T. G. (1965), "The Development and Change of Marine Organisms at the Palaeozoic-Mesozoic Boundary", Akademiya Nauk SSSR, Trudy Paleontologicheskogo Instituta, 108: 1–431
• Shishova, N. A (1964), "Novyye Pozdnepermskiye Rabdomezonidy Sovetskogo Soyuza", Paleontologicheskii Zhurnal, 1964: 52–57