>I read that sporopollenin is best preserved in anaerobic-base
>environments, however can survive in some anaerobic/acid
>environments. It are least likely to survive in an oxidating
>environment like weathered/red porous rocks/soils. My question is this,
>if sporopollenin is quite invulnerable to most acids, why is it easily
>weathered in an oxidizing environment?
Time is certainly a factor. Any organic compound is subject to oxidation
under proper conditions. It is well established that redbeds (oxidized
iron deposits, generally combined with porosity of a sandstone, both of
which are inimical to sporopollenin) are normally barren of pollen and
spores and organic material in general. It is assumed that if organic
material was ever there it has long since been oxidized out. A standard
procedure for releasing pollen and spores from coal macerals is to treat
them with a mixture of concentrated nitric acid saturated with potassium
permangenate. I cannot imagine a stronger oxidizer than that. This stuff
completely oxidizes the carbonaceos material in the coal leaving
essentially sporopollenin as the surviving organic. However, the time of
exposure of the coal to this oxidizer must be optimized to prevent loss of
spores and pollen, which will certainly happen with continued exposure.
Chlorine bleach and sulfuric acid are also used.
>
>And, if it is in an (wow, 5 two letter words in a row!) oxidating,
>growndwater enviroment, what is to keep the sporopollenin from becoming
>silicified? (assuming the oxidating environment contained disolved
>silicates.)
Because the pollen and spore exines are made of a waxy substance impervious
to fluids, the mineral laden solutions cannot penetrate them, and thus no
permineralization would be possible. It is conceivable that the spore
material could be replaced by a mineral such as pyrite (or salt), but I
have never seen this or heard others discuss it. It is not a likely
scenario for the point in question.