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Showing results for tags 'thin section'.
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Hi people, I have a query regarding the contents of some siderite nodules from a Duckmantian fossil forest site in N Wales for my PhD project. I had thin sections made of parts of several nodules and they all seem to have an abundance of 'faecal pellets'; rounded, often curved (banana-ish) shaped, mostly stratified pellets. These pellets have been replaced by siderite (FeCO3) and sometimes include pyrite and seem to have been the locus for early sulphate reduction by bacteria before conditions arose for the siderite precipitation. I've attached SEM images of the thin sections showing some of these pellets. We have only found a couple of fragments of crustaceans (Euproops I believe) and the host sediments were fine sands and silts. All the images show individual pellets with scale bars but "pellet5" is a zoomed out image showing the abundance of the pellets. They are all replaced by an Fe-rich siderite and are all quartz free. "pellet6" is different with a mottled texture and some potential apatite mixed in. Let me know if anyone has seen similar textures before and/or what could have made them! The palaeoenvironment was purely freshwater with meandering river systems, with a dynamic lycopod dominated fossil forest ecosystem. pellet3.pdf pellet2.pdf pellet1.pdf pellet5.pdf pellet4.pdf
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The Rhynie Chert preserves one of the oldest terrestrial ecosystems, which is a hot spring environment. It's Lower Devonian, and the oldest know harvestman was also found there. These are some photographs of my thin sections from this environment. This first thin section is one of my favourites, it has several Aglaophyton major plants that contain fungal cysts of Palaeomyces gordoni, containing spores. These are more Aglaophyton major cross sections. In this and the one above, there are a few vascular bundles, these consist of thin-walled protoxylem cells, surrounded by thicker metaxylem cells, which is then surrounded by the phloem. In the cortex of some of these is the mycorrhizal fungi Glomites rhyniensis. Their hyphae look like a darker-coloured ring. These both are Aglaophyton major. This one has Aglaophyton major, as well as Retusotriletes spores and some more Palaeomyces gordoni cysts without spores. This section contains a few Retusotriletes spores. This has the plant Horneophyton lignieri in it, which had a rhizoids instead of roots. In the upper left of this one is an arthropod coprolite consisting mostly of spores. Lastly, this is a piece of the Rhynie Chert containing Aglaophyton major.
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