Two photos of an odd microfossil in a pebble of Mixon Alveolina Rock (Eocene, likely Bartonian) probably originating from reefs offshore of Selsey Bill, West Sussex. The photos are taken with a DSLR fitted with a microscope objective lens, and lit with a bright white LED torch at an oblique angle of about 35 degrees. The pebble has been polished with various abrasives. Previously on this website I’ve referred to this material as limestone. The material is variable, and the exact original in situ sources uncertain. If it all (or most of it) originates from a contiguous bed, then that strata varies in its composition from high calcium to high quartz sand content. However, some samples appear to have perhaps undergone a process of “silcretisation” (or maybe “calcitisation”?) so could possibly be called a silcrete (or maybe a “calcrete”?), andsome evidence of either can possibly be seen in these photos of this specimen. The material is generally known, amongst other names, as Mixon Rock, although I’m now choosing to call it Mixon Alveolina Rock to distinguish it from a limestone rock outcrop in Derbyshire called Mixon. Limestone, sandstone, or silcrete: I currently remain unsure of the the most accurate classification Concerning the odd microfossil shown in the photos, I’ve not yet come across other like examples in the other samples of this rock I’ve looked at.
…………………………………………………………………… A further two pictures (below) of the same microfossil taken with a hand-held USB microscope, one with polarizer on, the other off, both with dimensions: