File:Fossil wood (Valentine Formation, Miocene, 13-14 Ma; Ashfall Fossil Beds, Nebraska, USA).jpg
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English: Quartz-permineralized fossil wood from the Miocene of Nebraska, USA. (public display, Ashfall Fossil Beds State Historical Park, Nebraska, USA)
This is "petrified wood", a horrible term for what is actually called permineralization. Biogenic materials such as wood or bone have a fair amount of small-scale porosity. After burial, the porosity of wood or bone can get partially or completely filled up with minerals as groundwater or diagenetic fluids percolate through. The end result is a harder, denser material that retains the original three-dimensionality (or close to it). The wood or bone has become “petrified”. Well, no - it’s become permineralized. Not surprisingly, the most common permineralization mineral is quartz (SiO2). Sometimes, wood and bone have been permineralized with radioactive minerals such as black uraninite (UO2) or yellowish carnotite (K2(UO2)2(VO4)2·3H2O). From exhibit signage: Piece of "Petrified" Stump Valentine Formation, 80 feet below volcanic ash bed. Ashfall Park, 13-14 million years old Remnants of an ancient forest, including both rolled logs and upright stumps, occur in the Valentine Formation between 50 and 100 feet below the Ashfall ash bed. The detailed cell structure of this example is extremely well-preserved because it was buried quickly in river sand before it had a chance to rot. Chemicals dissolved in the local groundwater (in this case, silica) soon replaced the living woody tissue, leaving a perfect replica. Note the annual rings in this specimen are quite uniform in thickness, suggesting that the climate here didn't vary much from year to year between 13 and 14 million years ago. Stratigraphy: Valentine Formation, Miocene, 13-14 Ma Locality: Ashfall Fossil Beds, northeastern Nebraska, USA Info. at: en.wikipedia.org/wiki/Ashfall_Fossil_Beds |
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| Source | https://www.flickr.com/photos/47445767@N05/52268782208/ |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/52268782208. It was reviewed on 12 November 2022 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 19:13, 12 November 2022 | | 3,008 × 2,000 (3.56 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/52268782208/ with UploadWizard |
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