Miaogou Formation
{{Short description|Early Cretaceous geological formation in China}}
{{Infobox rockunit
| name = Miaogou Formation
| type = Geological formation
| age = late Early Cretaceous, {{fossilrange|earliest=Barremian|Aptian|Albian|~Aptian–Albian}}
| period = Early Cretaceous
| region = Inner Mongolia
| country = {{flag|China}}
| coordinates = {{coord|40|12|N|105|44|E|display=inline,title}}
| unitof = Yangtaiwatan Basin{{Cite journal |last1=Zhang |first1=Shuai |last2=Liu |first2=Lihui |last3=Liu |first3=Qinfu |last4=Zhang |first4=Bingjie |last5=Qiao |first5=Zhichuan |last6=Teppen |first6=Brian J. |date=February 2021 |title=Genesis of Palygorskite in the Neogene Baiyanghe Formation in Yangtaiwatan Basin, Northwest China, Based on the Mineralogical Characteristics and Occurrence of Enriched Trace Elements and Ree |journal=Clays and Clay Minerals |language=en |volume=69 |issue=1 |pages=23–37 |doi=10.1007/s42860-020-00104-7 |issn=0009-8604}}
| underlies = Baiyanghe Formation{{Cite journal |last1=Liu |first1=Lihui |last2=Zhang |first2=Shuai |last3=Liu |first3=Qinfu |last4=Liu |first4=Linsong |last5=Deng |first5=Youjun |date=September 2021 |title=Palaeoclimate, palaeosalinity and redox conditions control palygorskite claystone formation: an example from the Yangtaiwatan Basin, northwest China |journal=Clay Minerals |language=en |volume=56 |issue=3 |pages=210–221 |doi=10.1180/clm.2022.1 |issn=0009-8558}}
| overlies =
| thickness =
| prilithology = Sandstone, mudstone, muddy limestone and sandy conglomerate
| otherlithology =
| map = {{Location map|China#China Inner Mongolia
| relief = 1
| width = 250
| float = center
|coordinates={{coord|40|12|N|105|44|E}}
|pushpin_relief=1 }}
}}
The Miaogou Formation is a geological formation in Inner Mongolia, north China. While its absolute age is uncertain, it has been estimated to represent Early Cretaceous sediments based on the faunal composition. Dinosaur remains are among the fossils that have been recovered from the formation.
History and geology
The primary fossil-producing outcrop of the Miaogou Formation is the Maortu locality, which was discovered in 1959 by a joint expedition of Chinese and Russian paleontologists.{{Cite journal |last=Kliebanova |first=I. M. |year=1963 |title=阿拉善地区(毛尔图)白堊纪恐龙的埋藏 |trans-title=Deposit of Mesozoic Dinosaurs in Alashan (Maortu) |journal=Vertebrata PalAsiatica |language=zh |volume=7 |issue=1 |pages=52–58 |doi=10.19615/j.cnki.1000-3118.1963.01.005 |url=http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201003/P020100323319381519859.pdf}} Initial reports of the locality's fauna incorrectly assigned the fossils to either the Ulansuhai or Dashuigou formations, but a later discussion corrected this.
While the Miaogou Formation has not been absolutely dated, estimates based on charophytan, stratigraphic, and sedimentological studies have proposed a Barremian–Albian age range.{{Cite journal |last1=Van Itterbeeck |first1=Jimmy |last2=Bultynck|first2=Pierre |last3=Li |first3=Guo Wen |last4=Vandenberghe |first4=Noel |date=2001 |title=Stratigraphy, sedimentology and palaeoecology of the dinosaur-bearing Cretaceous strata at Dashuiguo (Inner Mongolia, People's Republic China) |url=https://biblio.naturalsciences.be/rbins-publications/bulletin-of-the-royal-belgian-institute-of-natural-sciences-earth-sciences/71-sup-2001/irscnb_p4087_01ec08x_71-sup_bulletin-3.pdf |journal=Bulletin van het Koninklijk Belgisch Instituut voor Natuurwetenschappen |volume=71 |pages=51–66}} However, a more narrow range (around Aptian-Albian) is implied based on the fossil animals found in the formation, which are inconsistent with Chinese Barremian faunas such as those associated with the Jehol Biota.
Paleoenvironment
Analysis of the formation's geology indicates that it represents a hot, humid environment with large lake systems. The formation's lower member preserves alluvial fan to braided stream deposits, while the upper member preserves meandering stream and lacustrine deposits.{{Cite journal |last=Wang |first=Zheng Qi |last2=Guan |first2=Tai Yang |year=2004 |title=Uranium pre-concentration in Miaogou Formation, Lower Cretaceous and its prospecting significance in Chaoshui Basin |url=https://inis.iaea.org/search/search.aspx?orig_q=RN:36114268 |journal=Uranium Geology |language=zh |volume=20 |issue=5 |pages=279–285}}
Fossil content
{{Paleobiota-key-compact}}
