Which preposition to use with fossilising

in Occurrences 3%

These investigations have demonstrated the existence, at great depths in the ocean, of living animals in some cases identical with, in others very similar to, those which are found fossilised in the white chalk.

by Occurrences 1%

Poets in dead and foreign languages were a form of fossils, and English poetswith that divine bloom upon them!they had a way of fossilising by spectacles, so that they never read them alive.

Which preposition to use with  fossilising