Lesson plan
Fusain
Fusain is a fossilised carbon deposit which has been identified as fossilised charcoal. 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. 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. The material is silky and crumbles on the touch. 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. Fusain shows characteristics diagnostic of pyrolysis in modern material: the cell walls of xylem are homogenized, and subsequently crack along their middles.
Article summary
Fusain is a fossilised carbon deposit which has been identified as fossilised charcoal. 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. 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. The material is silky and crumbles on the touch. 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. Fusain shows characteristics diagnostic of pyrolysis in modern material: the cell walls of xylem are homogenized, and subsequently crack along their middles.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.