Lacustrine oolitic limestone (Green River Formation, Eocene; near Tipton, Wyoming, USA) 2 : 無料・フリー素材/写真
Lacustrine oolitic limestone (Green River Formation, Eocene; near Tipton, 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 | Lacustrine oolitic limestone from the Eocene of Wyoming, USA.The Green River Formation of Utah-Colorado-Wyoming consists of multiple lake deposits of Eocene age. The unit is highly heterolithic, but is most famous for having oil shale deposits, marlstones with well-preserved fossils - especially fish, and chertified fossiliferous limestones ("Turritella Agate").Seen here is a Green River oolitic limestone. Such rocks are usually whitish to cream-colored and composed of sand-sized (1/16 to 2 mm in size), well rounded, concentrically-layered calcite or aragonite grains called oolites (also known as ooliths or ooids). Oolites form by rolling back and forth on a shallow seafloor by wave action, or sometimes on a shallow lake bed, as in this case. Oolites are forming today on the Bahamas Platform and in Great Salt Lake, Utah, USA. The technical geologic term for most oolitic limestones is “oolitic grainstone” or simply "oolite". Uncertainty surrounds the specific origin of oolites. Some conclude that oolites form by completely inorganic chemical precipitation of CaCO3 from water around some nucleus (a tiny shell or skeletal fragment or sediment grain). Others conclude that the presence of bacterial films on oolite grain surfaces plays a significant role in the precipitation of CaCO3 layers. However, the undoubted presence of bacteria does not necessarily indicate a biogenic origin for oolites - bacteria are everywhere.Stratigraphy: Laney Member, Green River Formation, EoceneLocality: unrecorded / undisclosed site in the Delaney Rim area, near the "town" of Tipton, Sweetwater County, southern Wyoming, USA------------------------Info. at:en.wikipedia.org/wiki/Green_River_Formationanden.wikipedia.org/wiki/Oolite |
| 撮影日 | 2023-11-03 17:34:15 |
| 撮影者 | James St. John |
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