Jaisalmer Formation
{{Short description|Geologic formation in India}}
{{Infobox Rockunit
|name=Jaisalmer Formation
|country={{flag|India}}
|thickness=Variable, typically {{convert|120|-|170|km|abbr=on}}
|image = File:Jaisalmer_Formation_Tharosaurus_type_locality.png
|imagesize = 250px
|caption = An outcrop of the Jaisalmer Formation which is the type locality for Tharosaurus indicus. Photographed between 2019-21.
|overlies=Lathi Formation
|underlies=Baisakhi Formation
|subunits=Badabag Member, Fort Member, Hamira Member, Jajiya Member, Joyan Member, Kuldhar Member
|unitof=
|paleocoordinates=
|region=
|namedby=Richard Dixon Oldham
|namedfor=Jaisalmer, India
|otherlithology=Limestone
|prilithology=Siltstone, sandstone
|period=Middle Jurassic
|age=Middle-Late Jurassic, {{fossilrange|Bajocian|Oxfordian}}
|type=Geological formation
|extent=Jaisalmer
|year_ts=1886Oldham, R.D., (1886). Preliminary note on the geology of northern
Jaisalmer. Record Geological Survey of India, 19,157-160.
|coordinates={{coord|26.911661|N|70.922928|E|display=inline,title}}
}}
The Jaisalmer Formation is a Middle to Late Jurassic-aged geologic formation located in India near the city of Jaisalmer that consists mainly of marine deposits.{{Cite journal |last1=Ahmad |first1=Faiz |last2=Quasim |first2=Mohammad Adnan |last3=Ahmad |first3=Abul Hasnat Masood |title=Review for "Microfacies and diagenetic overprints in the limestones of Middle Jurassic Fort Member (Jaisalmer Formation), Western Rajasthan, India: Implications for the depositional environment, cyclicity, and reservoir quality |journal=Geological Journal |volume=56 |issue=1 |pages=130–151 |date=January 2021 |url=http://dx.doi.org/10.1002/gj.3945/v1/review2 |doi=10.1002/gj.3945/v1/review2|url-access=subscription }} The formation was first identified and defined by geologist Richard Dixon Oldham in 1886.
Dinosaur remains are among the known fossils recovered from this formation.Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, Asia)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 593–600. {{ISBN|0-520-24209-2}}.
Strophodus jaisalmerensis, a hybodont, was named after this formation and the Jaisalmer District where its holotype was found.{{cite journal|year=2021|author=Krishna Kumara, Sunil Bajpaib, Pragya Pandeya, Triparna Ghosha, Debasish Bhattacharya|title=Hybodont sharks from the Jurassic of Jaisalmer, western India|journal=Historical Biology|volume=34|issue=6|page=953-963|doi=10.1080/08912963.2021.1954920}}
Sub-units
The Badabag, Fort, Joyan and Hamira members represent the Middle Jurassic Bajocian and Bathonian stages, while the Jajiya and Kuldhar members represent the Middle Jurassic Callovian and the Late Jurassic Oxfordian stages.
The Fort Member is the most extensively studied and consists of fine to medium grain sandstones and oolitic limestones.Narayanan, K., Subrahmanyan, M., Srinivasan, S., (1961). Geology of Jaisalmer. Unpublished report, Oil and Natural Gas Corporation Dehradun, India. The Badabag Member consists of intraformational conglomerate and is fossil bearing.
Paleoenvironment
The Jaisalmer district of India is a landlocked district in the state of Rajasthan. However, during the Middle Jurassic, the Jaisalmer Formation was located on the Tethyan coast of Gondwanan India. A marine paleoenvironment is supported by the presence of Hybodont sharks. The Kuldhar Member Limestone contained carbonate microfacies that also indicate a depositional environment composed mainly of lagoons, shoals and open marine environments.{{Cite journal |last=Asjad |first=Shaikh |last2=Khan |first2=K. F. |last3=Quasim |first3=M. A. |last4=Sachan |first4=H. K. |last5=Javed |first5=Aashna |date=2023-11-06 |title=Microfacies and stable isotope analysis of Kuldhar Member Limestone (Callovian–Oxfordian), Jaisalmer Basin, western Rajasthan: implications for depositional environment and diagenetic evolution |url=https://doi.org/10.1007/s13146-023-00905-6 |journal=Carbonates and Evaporites |language=en |volume=38 |issue=4 |pages=81 |doi=10.1007/s13146-023-00905-6 |issn=1878-5212|url-access=subscription }}
Paleofauna
{{expand_section|date=August 2022}}
{{paleobiota-key-compact}}
=Dinosaurs=
== Sauropods ==
== Theropods ==
= Other Reptiles =
| class="wikitable" align="center" | |||||
| colspan="6" align="center" | Reptiles of the Jaisalmer Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Locality | Material | Notes | Photos |
| Crocodylomorpha
| Indeterminate |Chandoo Village quarry | Scutes. | | | |||||
| Neodiapsida
| Indeterminate |Chandoo Village quarry | Teeth. | Either a sauropterygian, thalattosaurian, choristodere or an ichthyosauromorph. | |
= Fish =
= Crustaceans =
| class="wikitable" align="center" | |||||
| colspan="6" align="center" | Crustaceans of the Jaisalmer Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Locality | Material | Notes | Photos |
| Cytherella{{cite journal|last=Kumari |first=M. |year=2023 |title=Middle Jurassic Ostracodes from Joyan Member, Jaisalmer Formation, Jaisalmer, Rajasthan, India |journal=Paleontological Journal |volume=57 |issue=7 |pages=775–783 |doi=10.1134/S0031030123070055 }}
|C. indica | | | | | |||||
| Micropneumatocythere
|M. joyanensis | | | | | |||||
| Progonocythere
|P. khoslai | | | | | |||||
| Trichordis
|T. minuta | | | | |
= Ichnofossils =
- (?)Bichordites sp. – "Ichnofossils"Kulkarni, K.G., Borkar, V.D., Petare, T.J., (2008). Ichnofossils from the Fort Member (Middle Jurassic), Jaisalmer Formation, Rajasthan. Journal of the Geological Society of India, 71, 731-738
- Planolites .sp – "Ichnofossils"
- Rhizocorallium irregulare – "Ichnofossils"
- Rhizocorallium jenense – "Ichnofossils"
- Taenidium serpentinum – "Ichnofossils"
- Thalassinoides .sp – "Ichnofossils"