Strophomenid brachiopod (Marblehead Member, Columbus Limestone, Middle Devonian; lakehore outcrop near Marblehead Lighthouse, Ottawa County, Ohio, USA) 1 : 無料・フリー素材/写真
Strophomenid brachiopod (Marblehead Member, Columbus Limestone, Middle Devonian; lakehore outcrop near Marblehead Lighthouse, Ottawa County, Ohio, USA) 1 / 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 | Strophomenid brachiopod 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. 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.The thick-bedded Columbus Limestone is overlain by the thin-bedded Delaware Limestone. 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 is a major, continent-wide unconformity representing the Tippecanoe-Kaskaskia megasequence boundary (a type I sequence boundary).Seen here is a fossil strophomenid brachiopod in Ohio's Marblehead Peninsula. Brachiopods are sessile, benthic, filter-feeding, marine invertebrate. They first appear in Cambrian rocks and were abundant in Earth's oceans throughout the Paleozoic. They were also common in Mesozoic oceans, but are scarce in modern oceanic biotas. Brachiopods have two shells, called valves, that are usually calcareous (made of calcite - CaCO3 - calcium carbonate). Each shell of a brachiopod is bilaterally symmetrical, unlike each shell of a bivalve (clam).Classification: Animalia, Brachiopoda, Articulata (a.k.a. Rhynchonelliformea), StrophomenidaStratigraphy: Marblehead Member, Columbus Limestone, Eifelian Stage, lower Middle DevonianLocality: lakeshore outcrop near Marblehead Lighthouse, far-eastern Marblehead Peninsula, far-eastern Ottawa County, far-northern Ohio, USA (vicinity of 41° 32’ 11.14” North latitude, 82° 42’ 41.44” West longitude) |
| 撮影日 | 2007-06-11 17:02:04 |
| 撮影者 | James St. John |
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