Fossiliferous limestone (Columbus Limestone, Middle Devonian; Olentangy River at Lazarus Run confluence, Delaware County, Ohio, USA) 4 : 無料・フリー素材/写真
Fossiliferous limestone (Columbus Limestone, Middle Devonian; Olentangy River at Lazarus Run confluence, Delaware County, Ohio, USA) 4 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
|---|---|
| 説明 | Fossiliferous limestone in the Devonian of Ohio, USA.The Columbus Limestone is a significant carbonate unit in the Devonian of central and northern Ohio. It's actually part of a much more widespread sheet of Devonian carbonates that extends from New York State to the Midwest. The Columbus Limestone represents deposition in a subtropical, shallow-water, carbonate platform environment. The rocks are principally micritic limestones, fossiliferous wackestones, and fossiliferous packstones. Some chert nodules are present in the unit, but were not observed at the locality shown above. Fossils are typical Paleozoic shallow marine invertebrates - favositid corals, rugose corals, stromatoporoids, brachiopods, crinoids, blastoids, bryozoans, trilobites, bivalves, gastropods, cephalopods, rostroconchs, and tentaculites. Microfossils include conodonts and charophyte oogonia. Other fossils in the Columbus Limestone include vertebrates (fish), land plants (rare), and trace fossils. Some fossil horizons in the Columbus Limestone are partially silicified.At the locality shown above, the thick-bedded Columbus Limestone (= at & above water level) is overlain by the thin-bedded Delaware Limestone (not really visible here). The contact is a prominent disconformity (a type II sequence boundary). Biostratigraphic studies have shown that one conodont biozone is missing at the Columbus-Delaware contact in central Ohio, probably representing ~1 to 3 million years. The base of the Columbus Limestone (not visible here) is a major, continent-wide unconformity representing the Tippecanoe-Kaskaskia megasequence boundary (a type I sequence boundary).The prominent, straight fractures seen above are joints. Joints are fractures in rocks along which there has been no differential displacement - they are quite common. If offset has occurred, then the fracture is called a fault.Stratigraphy: uppermost Columbus Limestone, Eifelian Stage, lower Middle DevonianLocality: riverbank outcrop along the eastern side of the Olentangy River, just upstream from the Lazarus Run-Olentangy River confluence, western side of Chapman Road, south of the town of Delaware, central Delaware County, central Ohio, USA (~40º 14’ 00.22” North latitude, ~83º 03’ 39.70” West longitude) |
| 撮影日 | 2016-04-03 19:29:47 |
| 撮影者 | James St. John |
| タグ | |
| 撮影地 |