A strew from Paso Flores, Argentina. Fossil freshwater material. Diatomite sample from H Jay Margolis. Diatom sample from the collection of Colonel William D Fleming, US Army, MD FRMS. Mounted in Pleurax and dated 26/5/2026. Prepared by Michel Haak. Olympus BHB microscope using 450nm LED light. As well as the wider view I imaged a couple of regions using the 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Images stacked in Zerene (Pmax).
The material is mainly Aulacoseira sp. however there are examples from other genus in there. In one of the stacks there is what I think is Muelleria sp. (underside view with the rim towards the coverslip).
I’ve not been able to find out much about Paso Flores, however there was a 1965 book (“Diatomaceous deposits in Argentina”, By I.R. Cordini, 1965), which contains some information. I translated this and put it in my ‘Articles’ section (see here).