Phengite spherules from the Dalradian Bonahaven Formation, Islay, Scotland: glauconitized microfossils?

Publisher Website
Google Scholar
Abstract
Summary: Abundant spherules of phengite, 50—150 μm in diameter and with a radial texture, occur in mudstones at the top of the lowest member of the Bonahaven Formation. They have smooth, sharp boundaries, show flattening next to desiccation cracks and exhibit a restricted, bi-or tri-modal size distribution. It is inferred that the spherules represent infilled voids in a sediment which was deposited entirely from suspension. Accordingly, it is considered likely that the spherules are microfossils, although characteristic morphological features are lacking. They were probably infihled by glauconite, which was transformed to phengite during diagenesis and low-grade metamorphism.