Ermaying Formation
{{Short description|Geological formation in China}}
{{Infobox rockunit
| name = Ermaying Formation
| period = Anisian
| age = Anisian
~{{fossilrange|247|242}}
| image =
| imagesize =
| caption =
| type = Geological formation
| prilithology = Mudstone, sandstone
| otherlithology = Tuff
| unitof =
| subunits = Two Members
| underlies = Tongchuan Formation
| overlies = Heshanggou Formation
| thickness = Up to {{convert|600|m|ft}}
| area =
| map = {{Location map+ | China#China Shanxi
| relief = 1
| width = 250
| float = center
| places =
{{Location map~ | China#China Shanxi
| lat_deg = 37.5
| lon_deg = 113.0
| mark = Pink ff0080 pog.svg
| marksize = 12
}}
}}
| map_caption =
| location =
| coordinates = {{Coord|37|26|15|N|110|39|06|E|display=title, inline}}
| paleocoordinates = {{coord|38.2|N|90.5|E|display=inline}}
| region = Shaanxi, Shanxi, Inner Mongolia
| country = China
| extent =
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| thickness_ts =
}}
The Ermaying Formation is a geological formation of Anisian (Middle Triassic) age in north-central China.{{cite book|last=Desojo|first=J. B.|title=Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin|year=2013|isbn=978-1862393615}} It is found across much of the Ordos Basin, at outcrops within the provinces of Shaanxi, Shanxi, and Inner Mongolia. It is composed of up to 600 m thick sequence of mudstone and sandstone, overlying the Heshanggou Formation and underlying the Tongchuan Formation.{{Cite journal |last1=Zhu |first1=Zhicai |last2=Liu |first2=Yongqing |last3=Kuang |first3=Hongwei |last4=Newell |first4=Andrew J. |last5=Peng |first5=Nan |last6=Cui |first6=Mingming |last7=Benton |first7=Michael J. |date=2022-09-01 |title=Improving paleoenvironment in North China aided Triassic biotic recovery on land following the end-Permian mass extinction |journal=Global and Planetary Change |volume=216 |pages=103914 |doi=10.1016/j.gloplacha.2022.103914 |bibcode=2022GPC...21603914Z |issn=0921-8181|doi-access=free }}{{cite book|last=Sues|first=Hans-Dieter|title=Triassic life on land : the great transition|year=2010|publisher=Columbia University Press|location=New York|isbn=978-0231135221|author2=Fraser, Nicholas C.}} In the southern part of the Ordos Basin, the Zhifang Formation is equivalent to the Ermaying Formation.{{Cite journal |last1=Meng |first1=Qing-Ren |last2=Wu |first2=Guo-Li |last3=Fan |first3=Long-Gang |last4=Wei |first4=Hong-Hong |date=2019-03-01 |title=Tectonic evolution of early Mesozoic sedimentary basins in the North China block |url=https://www.researchgate.net/publication/329906040 |journal=Earth-Science Reviews |volume=190 |pages=416–438 |doi=10.1016/j.earscirev.2018.12.003 |bibcode=2019ESRv..190..416M |s2cid=135264897 |issn=0012-8252}}
The Ermaying Formation is divided into two members, each with a distinctive assemblage of tetrapod fossils. A 2013 study used SHRIMP U-Pb radiometric dating to assign an imprecise age of 245.9 ± 3.2 Ma for the upper member.{{Cite journal |last1=Liu |first1=Jun |last2=Li |first2=Lu |last3=Li |first3=Xing-Wen |date=2013 |title=SHRIMP U-Pb zircon dating of the Triassic Ermaying and Tongchuang formations in Shanxi, China and its stratigraphic implications |url=http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201305/P020130507382835293116.pdf |journal=Vertebrata PalAsiatica |volume=51 |issue=2 |pages=162–168}} A 2018 study assigned a more precise age of around 243.53 Ma based on three ash samples near the base of the upper member. This would indicate that the Upper Ermaying Formation is no older than the late Anisian stage.{{Cite journal |last1=Liu |first1=Jun |last2=Ramezani |first2=Jahandar |last3=Li |first3=Lu |last4=Shang |first4=Qing-Hua |last5=Xu |first5=Guang-Hui |last6=Wang |first6=Yan-Yin |last7=Yang |first7=Jia-Sheng |date=2018 |title=High-precision temporal calibration of Middle Triassic vertebrate biostratigraphy: U-Pb zircon constraints for the Sinokannemeyeria Fauna and Yonghesuchus |url=https://www.researchgate.net/publication/322242806 |journal=Vertebrata PalAsiatica |volume=56 |issue=1 |pages=16–24 |doi=10.19615/j.cnki.1000-3118.170808}}
A few studies apply the name "Ermaying Formation" to a sedimentary unit in the Yanshan belt, a fold-thrust belt northeast of Beijing. In the Yanshan belt, reported exposures of the formation are dated to the Late Triassic, lying below the Early Jurassic Xingshikou Formation.{{Cite journal |last1=Meng |first1=Qing-Ren |last2=Wei |first2=Hong-Hong |last3=Wu |first3=Guo-Li |last4=Duan |first4=Liang |date=2014-01-25 |title=Early Mesozoic tectonic settings of the northern North China craton |url=https://www.sciencedirect.com/science/article/pii/S004019511300680X |journal=Tectonophysics |volume=611 |pages=155–166 |doi=10.1016/j.tecto.2013.11.015 |bibcode=2014Tectp.611..155M |issn=0040-1951|url-access=subscription }}{{Cite journal |last1=Wei |first1=HongHong |last2=Wu |first2=GuoLi |last3=Duan |first3=Liang |date=2015-04-01 |title=Revisiting Triassic stratigraphy of the Yanshan belt |url=https://doi.org/10.1007/s11430-014-5042-x |journal=Science China Earth Sciences |language=en |volume=58 |issue=4 |pages=491–501 |doi=10.1007/s11430-014-5042-x |bibcode=2015ScChD..58..491W |s2cid=130672024 |issn=1869-1897|url-access=subscription }} The Yanshan belt exposures are also known as the Huzhangzi Formation, an alternative name proposed to reflect their chronological and geographic divergence from exposures in the Ordos Basin.
Paleobiota
The Ermaying Formation is notable for its diversity of well-preserved tetrapods.
The upper member occupies most of a biozone historically known as the Sinokannemeyeria fauna.{{Cite journal |last=Sun |first=Ai-Lin |date=1980 |title=Late Permian and Triassic terrestrial tetrapods of north China |trans-title= |url=https://naturalhistory.si.edu/sites/default/files/media/translated_publications/Sun_80.pdf |journal=Vertebrata PalAsiatica |language=Chinese |volume=18 |issue=2 |pages=100–110}} This fossil assemblage has more recently been termed the Sinokannemeyeria-Shansisuchus Assemblage Zone, including approximately coeval sediments of the Kelamayi Formation in Xinjiang. The biozone also extends up to the early part of the Tongchuan Formation.{{Cite journal |last1=Liu |first1=Jun |last2=Sullivan |first2=Corwin |date=2017 |title=New discoveries from the Sinokannemeyeria-Shansisuchus Assemblage Zone: 3. Archosauriformes from Linxian, Shanxi, China |url=https://www.researchgate.net/publication/316776448 |journal=Vertebrata PalAsiatica |volume=55 |issue=2 |pages=110–128}}
Tetrapod burrows are known from the formation, occupying both large and small size classes. The larger burrow is reniform (kidney-shaped) in cross section, about {{Convert|13|cm|in}} in height and {{Convert|30|cm|in}} in width. It shallowly slopes down when seen from the side and smoothly undulates when seen from above. Scatches and grooves are readily visible on the inside. The burrow-maker was medium-sized animal, likely a juvenile dicynodont. The smaller burrows are low tapered chambers with incomplete or collapsed entry ramps. They may have been dug out by procolophonids or juvenile cynodonts.{{Cite journal |last1=Yang |first1=Jia-Sheng |last2=Yi |first2=Jian |last3=Dong |first3=Li-Yang |last4=Liu |first4=Jun |date=2018 |title=Tetrapod burrows from the Triassic Ermaying Formation of Shaanxi, China |url=https://www.researchgate.net/publication/324584246 |journal=Vertebrata PalAsiatica |volume=56 |issue=2 |pages=147–156 |doi=10.19615/j.cnki.1000-3118.180319}}{{Paleobiota-key-compact}}
= Synapsids =
Apart from the taxa listed here, fossils of an unnamed genus of kannemeyeriiform dicynodont have been found in the Upper Ermaying Formation at the Sanjiao site in Shanxi Province. Not counting Shansiodon, this unnamed form is the third "kannemeyeriid" genus known from the Upper Member, as it is distinct from both Parakannemeyeria and Sinokannemeyeria.{{Cite journal |last=Liu |first=Jun |date=2015 |title=New discoveries from the Sinokannemeyeria-Shansisuchus Assemblage Zone: 1. Kannemeyeriiformes from Shanxi, China |url=https://www.researchgate.net/publication/270875257 |journal=Vertebrata PalAsiatica |volume=53 |issue=1 |pages=16–28}}
== Cynodonts ==
| class="wikitable" align="center"
! colspan="6" align="center" |Cynodonts of the Ermaying Formation |
| Taxa
!Species !Material !Member !Notes !Images |
|---|
| Sinognathus{{Cite journal |last=Young |first=Chung-Chien |date=1959 |title=Note on the first cynodont from the Sinokannemeyeria-faunas in Shansi, China. |url=http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201106/P020110622317053665606.pdf |journal=Vertebrata PalAsiatica |volume=3 |issue=3 |pages=124–132}}
|A sinognathine trirachodontid cynodont. | |
