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Yixian Formation

The Yixian Formation (simplified Chinese:义县组; traditional Chinese:義縣組; pinyin: Yìxiàn zǔ) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period. It is known for its exquisitely preserved fossils, and is mainly composed of basalts interspersed with siliciclastic sediments.

Yixian Formation
Stratigraphic range: BarremianAptian
~129.7–122.1 Ma
TypeGeological formation
Unit ofJehol Group
Sub-unitsJingangshan Bed
Dawangzhangzi Bed
Jianshangou Bed
Lujiatun Bed
UnderliesJiufotang Formation
OverliesDabeigou Formation?, Tuchengzi Formation
Lithology
PrimaryBasalt
OtherSiliciclastic
Location
Coordinates41°31′59″N121°14′18″E /41.5330°N 121.2383°E /41.5330; 121.2383Coordinates: 41°31′59″N121°14′18″E /41.5330°N 121.2383°E /41.5330; 121.2383
RegionLiaoning
CountryChina
Yixian Formation (China)
Show map of China
Yixian Formation (Liaoning)
Show map of Liaoning

Contents

Japanese occupation

The potential importance of the Yixian Formation was initially recognized during the time the Empire of Japan occupied China's Rehe ("Jehol") Province after the First battle of Hopei in 1933. Many Japanese scientists had noticed fossil remains of extinct fish and reptiles, possibly the champsosaurs. These initial fossil discoveries made by Japanese scientists vanished once World War II ended in 1945.

Chinese rediscovery

By 1949, when administration of the area passed to the Chinese Communist Party and its leader Mao Zedong, the fossils of Yixian were studied only by Chinese scientists. It was not until the 1990s when remarkable fossils of birds and dinosaurs were excavated. Since 1996, a number of dinosaur fossils that have revolutionized knowledge of these animals have been found at Yixian; among them are the first known non-avian theropods with feathers.

For some time, the formation was believed to be from the Late JurassicEarly Cretaceous boundary, some 145 mya (million years ago). Radiometric dating has since resolved it to be younger; it is now considered to have been deposited in the Barremian to early Aptian, some 125–121 mya.

The Yixian Formation forms the lowest part of the Jehol group, defined by Gu (1962 and 1983) as a group of geological formations including the Jehol Coal-bearing Beds, the Jehol Oil Shale Beds, and the Jehol Volcanic Rocks. The Yixian Formation is preceded by the older Daohugou Beds, of uncertain Jurassic or Early Cretaceous age, which are sometimes considered part of the Jehol group. The Yixian Formation (including the synonymous Jingangshan, Tuhulu, Jianchang, Lower Volcanic and Volcanic Rock formations) is followed stratigraphically by the slightly younger Jiufotang Formation and the Fuxin Formation. Chiappe et al. argued in 1999 that the oldest beds of the Yixian (those bearing a fauna dominated by confuciusornithid birds) were best separated as a distinct formation, called the Chaomidianzi Formation, with a type locality at the village of Sihetun, approximately 25 km south of Beipiao City. However, this classification has fallen out of favor, and the Chaomidianzi Formation is disused as a synonym for the Jianshangou Bed of the Yixian Formation.

The Dabeigou Formation in Fengning, Hebei Province may immediately precede the Yixian, or it may be equivalent to the oldest Yixian beds. The Yixian also overlies the Tuchengzi Formation in places.

The Yixian Formation is divided into the following subunits, from most recent to oldest: (ages when available from Chang et al., 2009)

  • Jingangshan Bed (youngest, 122.1 Ma)
  • Dawangzhangzi Bed
  • Lujiatun Bed (123.2 Ma)
  • Jianshangou Bed (124.1 Ma)
  • Dakangpu Bed (~125 Ma)
  • Basalt base (oldest, 129.7 Ma)

New high-precision 40Ar/39Ar dating provided ages of 125.8 ± 1.0 Ma and 126.0 ± 0.8 Ma for two basaltic samples from the Lujiatun Unit.

The Yixian Formation represents the second of three major faunal phases that characterize the Jehol Biota, mainly based on changes in invertebrate diversity. In the Yixian, ostracods (seed shrimp) had diversified considerably, despite a very low diversity in the earlier Dabeigou Formation. Other major invertebrate groups in the Yixian include clam shrimp and insects. Insects, as a group, experienced their largest diversification of the entire Mesozoic era in the Yixian. On the other hand, some invertebrate groups, such as bivalves and gastropods (snails and slugs), were numerous but low in diversity, being mainly represented by one or two dominant species (Arguniella in the case of the bivalves).

Studies of vertebrates have shown support for the division of the Jehol into phases, and the diversity of fish in the Yixian was distinct from older and younger formations, with Lycoptera as the dominant species. The Yixian preserves the first Jehol dinosaurs and pterosaurs (which have not been found in the older Dabeigou Formation), and the first major radiation of birds (only one bird species is known from the Dabeigou). The Yixian also preserves the largest (and only) mammal radiation so far known from the Jehol group. Most vertebrates showed a tendency to climb trees or become arboreal, including many tree-dwelling birds, and climbing mammals and lizards.

Plant life reached its Jehol biota peak in the Yixian. Five species of flowering plant were present (three of Archaefructus, one of Archaeamphora and one of Hyrcantha (formerly Sinocarpus), as were a variety of horsetails that closely resembled modern species. It is possible that increasing animal and plant diversity were linked. The Yixian is characterized by extensive forests, dominated by trees such as ginkgoes, conifers, cycads, and seed fern trees. Ground cover plants included lycopods, horsetails, ferns, and primitive flowering plants, which were rare compared to the others.

This plant life grew around a series of freshwater lakes, provided with abundant minerals thanks to periodic volcanic eruptions. Volcanic activity, along with periodic wildfires, and noxious gasses released from the lake bottoms caused the ecosystem to be continually destroyed and regrown. This, along with the wide diversity of habitats in the surrounding region, may have contributed to the fast diversification of life forms present in the Yixian ecosystem.

With the diversity of plant life in the Yixian well known, including examples of a variety of petrified wood and growth rings, and with the help of chemical analysis, scientists have been able to determine the climate of the formation. The Yixian flora was dominated by conifers closely related to modern species that are found mainly in subtropical and temperate upland forests. The presence of ferns, cycads, and horsetails indicates a generally humid climate. However, evidence from the growth rings of petrified wood indicates that the humidity and water supply dropped regularly. This shows that the wet, humid conditions were punctuated by dry seasons, in which the environment became more arid. Evidence from the study of oxygen isotopes has shown that the average yearly temperature during this time period was 10 degrees celsius (50 degrees Fahrenheit), significantly colder than once thought. This indicates a temperate climate with unusually cold winters for the generally warm Mesozoic era, possibly due to northern China's high latitude during this time. A study by Wu et al. (2013) concluded that orbital forcing, which is the effect on climate caused by shifts in the tilt of the Earth's axis and by the shape of the Earth's orbit, contributed to the climate fluctuations of this formation.

The Yixian Formation is well known for its great diversity of well-preserved specimens and its feathered dinosaurs, such as the large tyrannosauroid Yutyrannus, the therizinosaur Beipiaosaurus and various small birds, along with a selection of non-theropod dinosaurs, such as Bolong, Dongbeititan and Psittacosaurus. Despite popular assumption, Microraptor does not hail from this formation, instead hailing from the younger Jiufotang Formation. However, other microraptorines, such as Sinornithosaurus and Graciliraptor, did indeed inhabit the Yixian. Other biota included the troodontid Mei, the dromaeosaurid Tianyuraptor, the large compsognathid Sinocalliopteryx and the tyrannosauroid Dilong.[citation needed]It could have also had a limnic eruption that preserved the fossils excluding Dongbeititan.

  1. Zhou, Z (2006). "Evolutionary radiation of the Jehol Biota: chronological and ecological perspectives". Geological Journal. 41 (3–4): 377–393. doi:10.1002/gj.1045.
  2. Swisher, Carl C., Wang, Yuan-qing, Wang, Xiao-lin, Xu, Xing, Wang, Yuan. (1999). "Cretaceous age for the feathered dinosaurs of Liaoning, China". Nature 400:58–61 1 July 1999.
  3. Gu, Z.W. (1983) "On the boundary of non-marine Jurassic and Cretaceous in China" in: "Nanjing Institute of Geology and Paleontology, Academica Sinica" "Stratigraphical Chart in China with Explanatory Text" Science Press, Beijing 1983:65–82.
  4. Sha, Jingeng (2007). "Cretaceous Stratigraphy of northeast China: non-marine and marine correlation". Cretaceous Research. 28 (2): 146–170. doi:10.1016/j.cretres.2006.12.002.
  5. Chiappe, L.M., Ji, S.A., Ji, Q., and Norell, M.A. (1999). "Anatomy and systematics of the Confuciusornithidae (Aves) from the Mesozoic of North-eastern China." Bulletin of the American Museum of Natural History, 1999.
  6. Chen, P.; Wang, Q.; Zhang, H.; Cao, M.; Li, W.; Wu, S.; Shen, Y. (2005). "Jianshangou Bed of the Yixian Formation in west Liaoning, China". Science in China Series D: Earth Sciences. 48 (3): 298–312. doi:10.1360/04yd0038. S2CID 130825449.
  7. Wang, Y.; Ken, S.; Zhang, W.; Zheng, S. (2006). "Biodiversity and palaeoclimate of the Middle Jurassic floras from the Tiaojishan Formation in western Liaoning, China". Progress in Natural Science. 16 (1): 222–230. doi:10.1080/10020070612330087.
  8. Chang, S. C.; Zhang, H.; Renne, P. R.; Fang, Y. (2009). "High-precision 40Ar/39Ar age for the Jehol Biota". Palaeogeography, Palaeoclimatology, Palaeoecology. 280 (1): 94–104. doi:10.1016/j.palaeo.2009.06.021.
  9. Su-Chin Chang, Ke-Qin Gao, Chang-Fu Zhou & Fred Jourdan (2017). New chronostratigraphic constraints on the Yixian Formation with implications for the Jehol Biota. Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication); doi: https://doi.org/10.1016/j.palaeo.2017.09.026
  10. Wang, Y., Zheng, S., Yang, X., Zhang, W., and Ni, Q. (2006). "The biodiversity and palaeoclimate of conifer floras from the Early Cretaceous deposits in western Liaoning, northeast China." International Symposium on Cretaceous Major Geological Events and Earth System, 56A.
  11. Amiot, R.; Wang, X.; Zhou, Z.; Xiaolin Wang, X.; Buffetaut, E.; Lécuyer, C.; Ding, Z.; Fluteau, F.; Hibino, T.; Kusuhashi, N.; Mo, J.; Suteethorn, V.; Yuanqing Wang, Y.; Xu, X.; Zhang, F. (2011). "Oxygen isotopes of East Asian dinosaurs reveal exceptionally cold Early Cretaceous climates". Proceedings of the National Academy of Sciences. 108 (13): 5179–5183. doi:10.1073/pnas.1011369108. PMC3069172. PMID 21393569.
  12. Wu, Huaichun; Zhang, Shihong; Jiang, Ganqing; Yang, Tianshui; Guo, Junhua; Li, Haiyan (2013). "Astrochronology for the Early Cretaceous Jehol Biota in Northeastern China". Palaeogeography, Palaeoclimatology, Palaeoecology. 385: 221–228. doi:10.1016/j.palaeo.2013.05.017.

Yixian Formation
Yixian Formation Language Watch Edit The Yixian Formation simplified Chinese 义县组 traditional Chinese 義縣組 pinyin Yixian zǔ is a geological formation in Jinzhou Liaoning People s Republic of China that spans 11 million years during the early Cretaceous period It is known for its exquisitely preserved fossils and is mainly composed of basalts interspersed with siliciclastic sediments 1 Yixian Formation Stratigraphic range Barremian Aptian 129 7 122 1 Ma PreꞒ Ꞓ O S D C P T J K Pg NTypeGeological formationUnit ofJehol GroupSub unitsJingangshan Bed Dawangzhangzi Bed Jianshangou Bed Lujiatun BedUnderliesJiufotang FormationOverliesDabeigou Formation Tuchengzi FormationLithologyPrimaryBasaltOtherSiliciclasticLocationCoordinates41 31 59 N 121 14 18 E 41 5330 N 121 2383 E 41 5330 121 2383 Coordinates 41 31 59 N 121 14 18 E 41 5330 N 121 2383 E 41 5330 121 2383RegionLiaoningCountry ChinaYixian Formation China Show map of ChinaYixian Formation Liaoning Show map of Liaoning Contents 1 History 1 1 Japanese occupation 1 2 Chinese rediscovery 2 Dating 3 Ecology 4 Climate 5 Paleobiota 6 See also 7 ReferencesHistory EditJapanese occupation Edit The potential importance of the Yixian Formation was initially recognized during the time the Empire of Japan occupied China s Rehe Jehol Province after the First battle of Hopei in 1933 Many Japanese scientists had noticed fossil remains of extinct fish and reptiles possibly the champsosaurs These initial fossil discoveries made by Japanese scientists vanished once World War II ended in 1945 Chinese rediscovery Edit By 1949 when administration of the area passed to the Chinese Communist Party and its leader Mao Zedong the fossils of Yixian were studied only by Chinese scientists It was not until the 1990s when remarkable fossils of birds and dinosaurs were excavated Since 1996 a number of dinosaur fossils that have revolutionized knowledge of these animals have been found at Yixian among them are the first known non avian theropods with feathers Dating EditFor some time the formation was believed to be from the Late Jurassic Early Cretaceous boundary some 145 mya million years ago Radiometric dating has since resolved it to be younger it is now considered to have been deposited in the Barremian to early Aptian some 125 121 mya 2 The Yixian Formation forms the lowest part of the Jehol group defined by Gu 1962 and 1983 as a group of geological formations including the Jehol Coal bearing Beds the Jehol Oil Shale Beds and the Jehol Volcanic Rocks 3 The Yixian Formation is preceded by the older Daohugou Beds of uncertain Jurassic or Early Cretaceous age which are sometimes considered part of the Jehol group The Yixian Formation including the synonymous Jingangshan Tuhulu Jianchang Lower Volcanic and Volcanic Rock formations is followed stratigraphically by the slightly younger Jiufotang Formation and the Fuxin Formation 4 Chiappe et al argued in 1999 that the oldest beds of the Yixian those bearing a fauna dominated by confuciusornithid birds were best separated as a distinct formation called the Chaomidianzi Formation with a type locality at the village of Sihetun approximately 25 km south of Beipiao City 5 However this classification has fallen out of favor and the Chaomidianzi Formation is disused as a synonym for the Jianshangou Bed of the Yixian Formation 6 The Dabeigou Formation in Fengning Hebei Province may immediately precede the Yixian or it may be equivalent to the oldest Yixian beds 1 The Yixian also overlies the Tuchengzi Formation in places 7 The Yixian Formation is divided into the following subunits from most recent to oldest ages when available from Chang et al 2009 8 Jingangshan Bed youngest 122 1 Ma Dawangzhangzi Bed Lujiatun Bed 123 2 Ma Jianshangou Bed 124 1 Ma Dakangpu Bed 125 Ma Basalt base oldest 129 7 Ma New high precision 40Ar 39Ar dating provided ages of 125 8 1 0 Ma and 126 0 0 8 Ma for two basaltic samples from the Lujiatun Unit 9 Ecology EditThe Yixian Formation represents the second of three major faunal phases that characterize the Jehol Biota mainly based on changes in invertebrate diversity In the Yixian ostracods seed shrimp had diversified considerably despite a very low diversity in the earlier Dabeigou Formation Other major invertebrate groups in the Yixian include clam shrimp and insects Insects as a group experienced their largest diversification of the entire Mesozoic era in the Yixian On the other hand some invertebrate groups such as bivalves and gastropods snails and slugs were numerous but low in diversity being mainly represented by one or two dominant species Arguniella in the case of the bivalves 1 Studies of vertebrates have shown support for the division of the Jehol into phases and the diversity of fish in the Yixian was distinct from older and younger formations with Lycoptera as the dominant species The Yixian preserves the first Jehol dinosaurs and pterosaurs which have not been found in the older Dabeigou Formation and the first major radiation of birds only one bird species is known from the Dabeigou The Yixian also preserves the largest and only mammal radiation so far known from the Jehol group Most vertebrates showed a tendency to climb trees or become arboreal including many tree dwelling birds and climbing mammals and lizards 1 Plant life reached its Jehol biota peak in the Yixian Five species of flowering plant were present three of Archaefructus one of Archaeamphora and one of Hyrcantha formerly Sinocarpus as were a variety of horsetails that closely resembled modern species It is possible that increasing animal and plant diversity were linked The Yixian is characterized by extensive forests dominated by trees such as ginkgoes conifers cycads and seed fern trees Ground cover plants included lycopods horsetails ferns and primitive flowering plants which were rare compared to the others 1 This plant life grew around a series of freshwater lakes provided with abundant minerals thanks to periodic volcanic eruptions Volcanic activity along with periodic wildfires and noxious gasses released from the lake bottoms caused the ecosystem to be continually destroyed and regrown This along with the wide diversity of habitats in the surrounding region may have contributed to the fast diversification of life forms present in the Yixian ecosystem 1 Climate EditWith the diversity of plant life in the Yixian well known including examples of a variety of petrified wood and growth rings and with the help of chemical analysis scientists have been able to determine the climate of the formation The Yixian flora was dominated by conifers closely related to modern species that are found mainly in subtropical and temperate upland forests The presence of ferns cycads and horsetails indicates a generally humid climate However evidence from the growth rings of petrified wood indicates that the humidity and water supply dropped regularly This shows that the wet humid conditions were punctuated by dry seasons in which the environment became more arid 10 Evidence from the study of oxygen isotopes has shown that the average yearly temperature during this time period was 10 degrees celsius 50 degrees Fahrenheit significantly colder than once thought This indicates a temperate climate with unusually cold winters for the generally warm Mesozoic era possibly due to northern China s high latitude during this time 11 A study by Wu et al 2013 concluded that orbital forcing which is the effect on climate caused by shifts in the tilt of the Earth s axis and by the shape of the Earth s orbit contributed to the climate fluctuations of this formation 12 Paleobiota EditMain article Paleobiota of the Yixian Formation The Yixian Formation is well known for its great diversity of well preserved specimens and its feathered dinosaurs such as the large tyrannosauroid Yutyrannus the therizinosaur Beipiaosaurus and various small birds along with a selection of non theropod dinosaurs such as Bolong Dongbeititan and Psittacosaurus Despite popular assumption Microraptor does not hail from this formation instead hailing from the younger Jiufotang Formation However other microraptorines such as Sinornithosaurus and Graciliraptor did indeed inhabit the Yixian Other biota included the troodontid Mei the dromaeosaurid Tianyuraptor the large compsognathid Sinocalliopteryx and the tyrannosauroid Dilong citation needed It could have also had a limnic eruption that preserved the fossils excluding Dongbeititan See also EditList of fossil sites with link directory List of dinosaur bearing fossil sitesReferences Edit a b c d e f Zhou Z 2006 Evolutionary radiation of the Jehol Biota chronological and ecological perspectives Geological Journal 41 3 4 377 393 doi 10 1002 gj 1045 Swisher Carl C Wang Yuan qing Wang Xiao lin Xu Xing Wang Yuan 1999 Cretaceous age for the feathered dinosaurs of Liaoning China Nature 400 58 61 1 July 1999 Gu Z W 1983 On the boundary of non marine Jurassic and Cretaceous in China in Nanjing Institute of Geology and Paleontology Academica Sinica Stratigraphical Chart in China with Explanatory Text Science Press Beijing 1983 65 82 Sha Jingeng 2007 Cretaceous Stratigraphy of northeast China non marine and marine correlation Cretaceous Research 28 2 146 170 doi 10 1016 j cretres 2006 12 002 Chiappe L M Ji S A Ji Q and Norell M A 1999 Anatomy and systematics of the Confuciusornithidae Aves from the Mesozoic of North eastern China Bulletin of the American Museum of Natural History 1999 Chen P Wang Q Zhang H Cao M Li W Wu S Shen Y 2005 Jianshangou Bed of the Yixian Formation in west Liaoning China Science in China Series D Earth Sciences 48 3 298 312 doi 10 1360 04yd0038 S2CID 130825449 Wang Y Ken S Zhang W Zheng S 2006 Biodiversity and palaeoclimate of the Middle Jurassic floras from the Tiaojishan Formation in western Liaoning China Progress in Natural Science 16 1 222 230 doi 10 1080 10020070612330087 Chang S C Zhang H Renne P R Fang Y 2009 High precision 40Ar 39Ar age for the Jehol Biota Palaeogeography Palaeoclimatology Palaeoecology 280 1 94 104 doi 10 1016 j palaeo 2009 06 021 Su Chin Chang Ke Qin Gao Chang Fu Zhou amp Fred Jourdan 2017 New chronostratigraphic constraints on the Yixian Formation with implications for the Jehol Biota Palaeogeography Palaeoclimatology Palaeoecology advance online publication doi https doi org 10 1016 j palaeo 2017 09 026 Wang Y Zheng S Yang X Zhang W and Ni Q 2006 The biodiversity and palaeoclimate of conifer floras from the Early Cretaceous deposits in western Liaoning northeast China International Symposium on Cretaceous Major Geological Events and Earth System 56A Amiot R Wang X Zhou Z Xiaolin Wang X Buffetaut E Lecuyer C Ding Z Fluteau F Hibino T Kusuhashi N Mo J Suteethorn V Yuanqing Wang Y Xu X Zhang F 2011 Oxygen isotopes of East Asian dinosaurs reveal exceptionally cold Early Cretaceous climates Proceedings of the National Academy of Sciences 108 13 5179 5183 doi 10 1073 pnas 1011369108 PMC 3069172 PMID 21393569 Wu Huaichun Zhang Shihong Jiang Ganqing Yang Tianshui Guo Junhua Li Haiyan 2013 Astrochronology for the Early Cretaceous Jehol Biota in Northeastern China Palaeogeography Palaeoclimatology Palaeoecology 385 221 228 doi 10 1016 j palaeo 2013 05 017 Retrieved from https en wikipedia org w index php title Yixian Formation amp oldid 1052574831, wikipedia, wiki, book,

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