Editing Maotianshan Shales (section)

== Preservation and taphonomy ==
[[File:Maotianshania-cylindrica.jpg|thumb|right|''[[Maotianshania|Maotianshania cylindrica]]'', a [[fossil]] [[Nematomorpha|nematomorph worm]], Early [[Cambrian]], Chengjiang Maotianshan Shales]]
{{further|Burgess shale type preservation}}
The fossils occur in a section of mudstone {{convert|50|m|ft}} thick in the [[Yuanshan Member]] of the [[Qiongzhusi Formation]]. The Yuanshan Member is extensive, covering multiple {{convert|10000|km2|sqmi}} of eastern Yunnan Province, where there are many scattered outcrops yielding fossils. Studies of the strata are consistent with a tropical environment with sea level changes and tectonic activity. The region is believed to have been a shallow sea with a muddy bottom. The preserved fauna is primarily [[benthic]] and was likely buried by periodic [[turbidity current]]s, since most fossils do not show evidence of post-mortem transport. Like the younger Burgess Shale fossils, the paleo-environment enabled preservation of non-mineralized, soft body parts. Fossils are found in thin layers less than an inch thick. The soft parts are preserved as aluminosilicate films, often with high oxidized iron content and often exhibiting exquisite details.

The Chengjiang beds are very deeply weathered, as evidenced by their low [[specific gravity]] (i.e., they are very lightweight).<ref name=Gaines2008>{{cite journal
|journal=Geology
|volume=36
|issue=10
|doi=10.1130/G24961A.1
|pages=755–758
|year=2008|title=Cambrian Burgess Shale–type deposits share a common mode of fossilization
|last1=Gaines
|first1=R. R.
|last2=Briggs
|first2=D. E. G.
|last3=Yuanlong
|first3=Z.
|bibcode=2008Geo....36..755G
}}</ref> Trace fossils are abundant.<ref name="Zhang2007">{{Cite journal | doi = 10.1111/j.1365-3121.2007.00765.x | title = Diminutive trace fossils in the Chengjiang Lagerstätte | year = 2007 | last1 = Zhang | first1 = X. G. | last2 = Bergström | first2 = J. | last3 = Bromley | first3 = R. G. | last4 = Hou | first4 = X. G. | journal = Terra Nova | volume = 19 | issue = 6 | pages = 407 | bibcode = 2007TeNov..19..407Z | s2cid = 129833092 }}</ref>