Haifanggou Formation

Haifanggou Formation
Stratigraphic range: Callovian-Oxfordian
~165–160 Ma
TypeGeological formation
UnderliesTiaojishan Formation
OverliesBeipiao Formation
(Separated by an unconformity)
Lithology
PrimaryConglomerate
OtherSandstone, mudstone, shale, coal
Location
Coordinates41°48′N 120°48′E / 41.8°N 120.8°E / 41.8; 120.8
Approximate paleocoordinates44°30′N 126°00′E / 44.5°N 126.0°E / 44.5; 126.0
RegionInner Mongolia
Country China
Type section
Named forHaifanggou
Named byLiaoning Stratigraphic Group
Year defined1978
Haifanggou Formation is located in China
Haifanggou Formation
Haifanggou Formation (China)
Haifanggou Formation is located in Inner Mongolia
Haifanggou Formation
Haifanggou Formation (Inner Mongolia)

The Haifanggou Formation (simplified Chinese: 海房沟组; traditional Chinese: 海房溝組; pinyin: Hǎifánggōu zǔ), also known as the Jiulongshan Formation (simplified Chinese: 九龙山组; traditional Chinese: 九龍山組; pinyin: Jiǔlóngshān zǔ), is a fossil-bearing rock deposit located near Daohugou (simplified Chinese: 道虎沟; traditional Chinese: 道虎溝) village of Ningcheng County, in Inner Mongolia, northeastern China.

The formation consists of coarse conglomerates, sandstone, mudstone, and thin coal layers deposited in deltaic and lacustrine environments.

The formation dates to the Callovian of the Middle Jurassic to the Oxfordian of the Late Jurassic.

The most prominent locality of the Haifanggou Formation are the Daohugou Beds, located near the village of Daohugou in southeastern Inner Mongolia. Other localities include Wuhuaxigou, Chentaizi, Jiangzhangzi, Wubaiding, Guancaishan, Haifenggou, Fanzhangzi, and Zhuanshanzi.

Dating

Daohugou bed

The age of the Daohugou bed has been debated, and a number of studies, using different methodologies, have reached conflicting conclusions. Various papers have placed the fossils here as being anywhere from the Middle Jurassic period (169 million years ago) to the Early Cretaceous period (122 ma). One of the first studies on the age of the Daohugou beds, published in 2004 by He et al., found them to be Early Cretaceous, only a few million years older than the overlying Jehol beds of the Yixian Formation. The 2004 study primarily used Argon–argon dating of a tuff within the Daohugou Beds to determine its age.

However, subsequent studies cast doubt on this relatively recent age. In a 2006 study, Gao & Ren criticized He et al. for not including enough specifics and detail in their paper, and also took issue with their radiometric dating of the Daohugou tuff. The tuff, Gao and Ren argued, contains crystals with a variety of diverse radiometric ages, some up to a billion years old, so using dates from only a few of these crystals could not determine the overall age of the deposits. Gao and Ren went on to defend a Middle Jurassic age for the beds based on biostratigraphy (the use of index fossils), and the bed's relationship to a layer that is known to mark the Middle Jurassic-Late Jurassic boundary.

Another study, published in 2006 by Wang et al., argued that the 159-164 million years old Tiaojishan Formation underlies, rather than overlies, the Daohugou Beds. Unlike the earlier study by Gao and Ren, Wang et al. found an overall similarity between the fossil animals found in the Daohugou Beds and those from the Yixian Formation. The authors stated that

"vertebrate fossils such as Liaoxitriton, Jeholopterus and feathered maniraptorans show much resemblance to those of the Yixian Formation. In other words, despite the absence of Lycoptera, a typical fish of the Jehol Biota, the Daohugou vertebrate assemblage is closer to that of the Early Cretaceous Jehol Biota than to any other biota."

Wang et al. concluded that the Daohugou probably represents the earliest evolutionary stages of the Jehol Biota, and that it "belongs to the same cycle of volcanism and sedimentation as the Yixian Formation of the Jehol Group." However, a later study by Ji et al. argued that the key indicator of the Jehol biota are the index fossils Peipiaosteus and Lycoptera. Under this definition, the earliest evolutionary stage of the Jehol Biota is represented by the Huajiying Formation, and the Daohugou Formation is excluded due to the absence of Lycoptera fossils. Later in 2006, Liu et al. published their own study of the age of the Daohugou beds, this time using Zircon Uranium-lead dating on the volcanic rocks overlying and underlying salamander-bearing layers (salamanders are often used as index fossils). Liu et al. found that the beds formed between 164 and 158 million years ago, in the Middle to Late Jurassic. A 2012 study by Gao and Shubin agreed with this assessment, and reported an Argon–argon date of 164 plus or minus 4 million years ago for the Daohugou horizon.

Animal fossil content

Arthropods

Insects
Genus Species Year Abundance Notes Images
Ahirmoneura A. neimengguensis 2008 A tangle-veined fly
Juracimbrophlebia
Aneuroderma A. oiodes 2021 2 specimens An earwig
Applanatiforceps A. angustus 2023 3 specimens An earwig
Archaboilus A. musicus 2012 1 specimen A stem-katydid
Ekpagloderma E. gracilentum 2023 1 specimen An earwig
Formosibittacus F. macularis 2008 1 specimen A hangingfly
Fortiholcorpa F. paradoxa 2013 1 specimen A Mecopteran
Juracimbrophlebia J. ginkgofolia 2012 1 specimen A hangingfly
Jurahylobittacus J. astictus 2008 1 specimen A hangingfly
Mesobunus M. dunlopi 2012 1 specimen A harvestman
Miriholcorpa M. forcipata 2013 1 specimen A Mecopteran
Mongolbittacus M. daohugoensis 2007 1 specimen A hangingfly
Pseudomantina P. baijuyii 2023 A cockroach
Pycnopolystoechotes P. striatus 2023 A lacewing
Sinojuraphis S. ningchengensis 2008 An aphid
Sinopalaeodermata S. concavum 2021 1 specimen An earwig
Stictopolystoechotes S. sparsulus 2023 A lacewing

Vertebrates

Genus Species Year Notes Images
Chunerpeton C. tianyiensis 2003 A cryptobranchid salamander
Castorocauda C. lutrasimilis 2006 A docodont (early mammaliaform)

Flora

Fossil plants
Genus Species State Abundance Notes Images
Coniopteris C. bella Liaoning A fern
C. burejensis Liaoning A fern
Sequoia S. jeholensis Ningcheng The earliest known redwood tree
Schmeissneria S. sinensis Liaoning A possible early flowering plant
Xingxueanthus X. sinensis Liaoning An possibly early flowering plant

See also


This page was last updated at 2023-11-11 22:56 UTC. Update now. View original page.

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