"Cedaria" woosteri (fossil trilobite) (Eau Claire Formation, Middle Cambrian; Warren County core # 2627, Ohio, USA) 2 : 無料・フリー素材/写真
"Cedaria" woosteri (fossil trilobite) (Eau Claire Formation, Middle Cambrian; Warren County core # 2627, Ohio, 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 | "Cedaria" woosteri (Whitfield, 1878) - fossil trilobite from the Cambrian of Ohio, USA. (OSU 46323, Orton Geology Museum, Ohio State University, Columbus, Ohio, USA)Trilobites are extinct marine arthropods. They first appear in Lower Cambrian rocks and went extinct at the end of the Permian. Trilobites had a calcitic exoskeleton and nonmineralizing parts underneath (legs, gills, gut, etc.). The calcite skeleton is most commonly preserved in the fossil record, although soft-part preservation is known in some trilobites (Ex: Burgess Shale and Hunsruck Slate). Trilobites had a head (cephalon), a body of many segments (thorax), and a tail (pygidium). Molts and carcasses usually fell apart quickly - most trilobite fossils are isolated parts of the head (cranidium and free cheeks), individual thoracic segments, or separated pygidia. The name "trilobite" was introduced in 1771 by Johann Ernst Immanuel Walch and refers to the tripartite division of the trilobite body - it has a central axial lobe that runs longitudinally from the head to the tail, plus two side lobes (pleural lobes).Trilobites are the state fossil in Ohio - they are most common in Upper Ordovician limestones and shales in the Cincinnati area of southwestern Ohio. Seen here is a much older, Cambrian-aged Ohio trilobite. It comes from a core drilled from 1987 to 1989 in northeastern Warren County, Ohio. The core was intended to be a stratigraphic reference section from the Upper Ordovician to Precambrian basement rocks. Instead of encountering igneous or metamorphic rocks below the Cambrian sedimentary cover, the core unexpectedly penetrated a thick, late Precambrian-aged sedimentary succession, which has been interpreted as a rift-basin fill. The rift fill sedimentary rocks were a new stratigraphic formation now called the Middle Run Formation (see photos elsewhere in the OGS core 2627 photo album). This trilobite comes from the Cambrian part of the core, in the Eau Clair Formation. It is a partial cephalon of "Cedaria" woosteri (formerly identified as Cedaria cf. Cedaria woosteri).Classification: Animalia, Arthropoda, Trilobita, Polymerida, CedariidaeStratigraphy: Eau Claire Formation, upper Middle CambrianLocality: 2821 feet deep (= feet below the surface well site), Ohio Division of Geological Survey core # 2627, American Aggregates Corporation limestone quarry (now flooded), just northeast of the town of Lytle, northwestern Wayne Township, northeastern Warren County, southwestern Ohio, USA---------------------------------Info. at:Babcock et al. (2014) - Cambrian (Guzhangian Stage) trilobites from Ohio, USA, and modification of the Cedaria Zone as used in Laurentia. Geologiska Föreningens i Stockholm Förhandlingar [GFF] 136: 6-15. |
| 撮影日 | 2014-04-06 17:08:45 |
| 撮影者 | James St. John |
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