Fusain

{{short description|Type of fossil deposit}} thumb|An example of fusain, charcoal that has been fossilized, found at a spoil pile from an underground coal mine in Grundy County, Illinois, US

'''Fusain''' is a fossilised carbon deposit which has been identified as fossilised charcoal.<ref name='Scott2000'>{{cite journal | author = Scott A | title = The Pre-Quaternary history of fire | journal = Palaeogeogr Palaeoclimatol Palaeoecol | volume = 164 | issue = 1–4 | pages = 281–329 | year = 2000 | doi = 10.1016/S0031-0182(00)00192-9 | bibcode = 2000PPP...164..281S }}</ref> There has been some controversy over its origin, whether it derives from logs under wet, anaerobic conditions or from charcoal associated with wildfires. Its origin from charcoal was decided to best fit the evidence by Tom Harris in the 1950s.<ref name="frs">{{Cite journal | last1 = Chaloner | first1 = W. G.| author-link = William Gilbert Chaloner | doi = 10.1098/rsbm.1985.0009 | doi-access = free| title = Thomas Maxwell Harris. 8 January 1903 – 1 May 1983 | journal = Biographical Memoirs of Fellows of the Royal Society | volume = 31 | pages = 228–260| year = 1985 | s2cid = 72170558}}</ref>{{rp|252}}

It is fibrous, black and opaque, and often preserves details of cell wall architecture. Wood-derived fusain usually takes the form of cubic blocks, whereas fusain from other plant material may take the form of thin films which are only visible under a microscope where the surrounding rock is dissolved by acid maceration.<ref name=Scott2000/> The material is silky and crumbles on the touch.<ref name=Scott2000/> The loss of volatile elements during combustion means that fusain fossils are usually smaller than the original organism, but this same factor makes them unlikely to be eaten by any animals (for they have no nutritional value), enhancing their preservation potential.<ref name=Scott2000/>

Fusain shows characteristics diagnostic of pyrolysis in modern material: the cell walls of xylem are homogenized, and subsequently crack along their middles.<ref name="Jones1991">{{Cite journal | doi = 10.1016/0031-0182(91)90180-Y | last1 = Jones | first1 = T. | last2 = Chaloner | first2 = W. | title = Fossil charcoal, its recognition and palaeoatmospheric significance | journal = Palaeogeography, Palaeoclimatology, Palaeoecology | volume = 97 | pages = 39–50 | year = 1991 | issue = 1–2 | bibcode = 1991PPP....97...39J }}</ref>

==References== {{reflist}}

== Further reading == *{{cite book | url = https://books.google.com/books?id=_29tNNeQKeMC&pg=PA18 | title = Paleobotany: The biology and evolution of fossil plants | isbn = 978-0-12-373972-8 | author1 = Taylor, Thomas N | author2 = Taylor, Edith L | author3 = Krings, Michael | year = 2009}}

* https://www.palaeocast.com/episode-22-fire-and-charcoal/#.U446-i-KWKO

Category:Fossil record of plants Category:Sedimentary rocks Category:Charcoal