File:Fossil nautiloid shell with original iridescent nacre in fossiliferous asphaltic limestone (Buckhorn Asphalt, Middle Pennsylvanian; Buckhorn Asphalt Quarry, Oklahoma, USA) 2.jpg
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Summary
[edit]DescriptionFossil nautiloid shell with original iridescent nacre in fossiliferous asphaltic limestone (Buckhorn Asphalt, Middle Pennsylvanian; Buckhorn Asphalt Quarry, Oklahoma, USA) 2.jpg |
English: Fossiliferous asphaltic limestone from the Pennsylvanian of Oklahoma, USA.
In paleontology, the term "lagerstätten" refers to sedimentary deposits having exceptionally well-preserved fossils, especially soft-bodied fossils. Such fossils can result from various geologic processes, including freezing (e.g., Siberian permafrost), desiccation (mummified carcasses in desert sands), and resin encasement (amber), just to name a few. The Buckhorn Lagerstätte of Oklahoma doesn't have soft-bodied fossils, but is remarkable in having aragonitic shelly fossils preserved with the original iridescent, colorful mother-of-pearl (nacre; nacreous aragonite). The Buckhorn dates to the late Middle Pennsylvanian, which makes it the oldest deposit in the world with aragonitic nacreous shelly fossils. What makes the Buckhorn special? It's an asphalt deposit - a paleo-seafloor oil seep deposit. A patch of seafloor was saturated by heavy oil (asphalt) that seeped out during the Pennsylvanian, well before the sediments were buried or lithified. Modern seafloor petroleum seeps are known in many places. Normally, the aragonite (CaCO3) and nacre (mother-of-pearl) of shells gets destroyed by recrystallization during diagenesis and post-diagenetic alteration events. At the Buckhorn deposit, the asphalt prevented the nacre from recrystallizing. The portion of the Pennsylvanian-aged Deese Group that contains the Buckhorn Asphalt is a fine-grained to coarse-grained siliciclastic and carbonate succession of marine rocks having well-preserved molluscs and plant fossils. In the past, the Buckhorn was considered to be shallow-water marine, but it’s been reinterpreted as an offshore, deeper-water deposit. Stratigraphy: limestone-clast conglomerate unconformity ----------- sandstone with carbonized logs mudstone thin gilsonite interval asphaltic limestone - has the best-preserved fossil material asphaltic sandstone chert-clast conglomerate - has woody debris, including large silicified Callixylon logs
The Buckhorn Asphalt sample seen here is asphaltic limestones from the cephalopod-rich association. The cephalopod-rich rocks are dominated by fossils of the body chamber portions of the shell (= where the squid hung out). These cephalopod-dominated rocks have been interpreted as submarine mass flow deposits. The sediments making up these flows were already saturated with petroleum. Stratigraphy: Buckhorn Asphalt, Deese Group, middle Desmoinesian, upper Middle Pennsylvanian. Locality: Buckhorn Asphalt Quarry, west of Route 177, ~10 miles south of Sulphur, southeastern Murray County, Arbuckle Mountains, southern Oklahoma, USA. Mostly synthesized from info. provided by Alex Nutzel and Thomas Yancey. |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/51193217618/ |
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@N05/51193217618. It was reviewed on 28 April 2023 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
28 April 2023
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current | 16:15, 28 April 2023 | 2,148 × 2,004 (2.8 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/51193217618/ with UploadWizard |
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Camera manufacturer | Canon |
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F-number | f/10 |
ISO speed rating | 80 |
Date and time of data generation | 01:35, 17 May 2021 |
Lens focal length | 9.681 mm |
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Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 18.0 (Macintosh) |
File change date and time | 04:47, 21 May 2021 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 01:35, 17 May 2021 |
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Custom image processing | Normal process |
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White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Standard |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 00:47, 21 May 2021 |
Unique ID of original document | 9A649E21692B2E680A8E875BB4528069 |
IIM version | 24,576 |