What is your evidence for volcanic origin of the silica? initial vegetation (Return ? petrified peat swamp veget.) coal I never found any glass shards or the 22A shift in the montmorillonite peaks expected in metavolcanic sed. when I studied them the sediments of Bentonites of the FV or GV Fms. I don't think there is any direct evident present (or preserved) in the pet. peat. One must use other type ? evidence including succession ? vegetation.