Gnishik Formation
| Gnishik Formation | |
|---|---|
| Stratigraphic range: Wordian (late Murgabian) ~ | |
| 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°00′N 45°00′E / 39.0°N 45.0°E |
| Approximate paleocoordinates | 9°06′S 41°24′E / 9.1°S 41.4°E |
| 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 dating back to the Wordian stage 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
- Cephalopods
- 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
- Rhynchonellata
- Cryptospirifer omeishanensis[15]
- Septospirigerella baissalensis[15]
- Terebratuloidea davidsoni[8]
- Crenispirifer sp.[15]
- Septospirigerella sp.[15]
- Strophomenata
- Stenolaemata
- 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
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
References
- ^ a b c Gnishik Formation in the Paleobiology Database
- ^ Leven, 1998, p.302
- ^ a b Saidi et al., 1997, p.198
- ^ Leven, 1998, p.301
- ^ Leven, 1998, p.308
- ^ Leven, 1998, p.314
- ^ Leven, 1998, p.320
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw Ruzhentsev & Sarycheva
- ^ a b c d e f g h i j Stepanov et al., 1969
- ^ a b c d Kropatcheva, 1999
- ^ a b c d e f g h i j Kotlyar et al., 1989
- ^ a b c d e f g h i j k Morozova, 1970
- ^ a b c d Ezaki, 1991
- ^ Stukalina, 1999
- ^ a b c d e f Nakamura & Golshani, 1981
- ^ a b c Shishova, 1964
- ^ Gennari & Rettori, 2019
Bibliography
- Geology
- Paleontology
- Geologic formations of Armenia
- Geologic formations of Azerbaijan
- Geologic formations of Iran
- Permian System of Asia
- Permian Armenia
- Permian Azerbaijan
- Permian Iran
- Wordian
- Limestone formations
- Open marine deposits
- Permian southern paleotropical deposits
- Paleontology in Armenia
- Paleontology in Azerbaijan
- Paleontology in Iran