"Turritella Agate" (fossiliferous chert) (Laney Member, Green River Formation, Middle Eocene; near Wamsutter, Wyoming, USA) 2 : 無料・フリー素材/写真
"Turritella Agate" (fossiliferous chert) (Laney Member, Green River Formation, Middle Eocene; near Wamsutter, Wyoming, USA) 2 / James St. John
ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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説明 | "Turritella Agate" from the Eocene of Wyoming, USA.Of all the molluscs, the gastropods (snails) have made the most ecological adaptations. They can be found in almost all fundamental environments: marine, freshwater, terrestrial. Most gastropods live in the ocean, and have a single, asymmetrically coiled, external shell of calcium carbonate (CaCO3 - usually aragonite). The hard calcareous shell is the most easily fossilized part of the gastropod. The soft parts of a snail (the “slug” portion) include a well developed head having eyes, tentacles, and a mouth, and a well developed, strong, muscular foot used principally for locomotion. The shell is carried upright on the snail’s back, or is partially dragged behind. When threatened by a predator, many snails can retract their soft parts into the shell’s interior for protection. Many fossil snails in the Paleozoic rock record are often not well preserved, or are preserved as internal molds. The original aragonite of many gastropod shells is not stable on geologic time scales, and often recrystallizes or dissolves completely away. Fossil snail shells in Mesozoic and Cenozoic rocks are usually better preserved.The rock seen here is fossiliferous chert packed with fossil snails. This material is popular with rockhounds and lapidarists, who call it "Turritella Agate". Well, it's not agate - it's fossiliferous chert. And the snails aren't Turritella, they are Elimia tenera. This rock is actually a chertified lacustrine limestone.Classification: Animalia, Mollusca, Gastropoda, Cerithioidea, PleuroceridaeStratigraphy: Laney Member, Green River Formation, Middle EoceneLocality: unrecorded site near the town of Wamsutter, southern Wyoming, USA |
撮影日 | 2019-11-22 12:24:20 |
撮影者 | James St. John |
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