Straparollus planodorsatus (fossil gastropod) (Maxville Limestone, Mississippian; Pleasant Valley Limestone Quarry, Muskingum County, Ohio, USA) 3 : 無料・フリー素材/写真
Straparollus planodorsatus (fossil gastropod) (Maxville Limestone, Mississippian; Pleasant Valley Limestone Quarry, Muskingum County, Ohio, USA) 3 / 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 | Straparollus planodorsatus (Meek & Worthen, 1860) - fossil gastropods from the Mississippian of Ohio, USA. (millimeter scale)The Maxville Limestone is the only Middle to Late Mississippian-aged stratigraphic unit in Ohio. Its outcrop belt is not extensive - it principally occurs in Muskingum County and Perry County in eastern and southeastern Ohio. The Maxville Formation can also be found as cobbles and pebbles in the basal Sharon Formation (Lower Pennsylvanian), which disconformably overlies Ohio's Mississippian rocks. Paleohills, or erosional outliers, of Maxville Limestone have also been identified.Seen above are weathered-out fossils from the Maxville Limestone at a quarry in western Muskingum County, Ohio. The quarry targets Maxville Limestone and crushes it for use as road gravel, fill, rip-rap, and erosion-control blocks. The Maxville here is an erosional outlier that is described in Stout (1918).The exposed stratigraphy at this quarry includes basal Pennsylvanian sedimentary rocks disconformably overlying Mississippian Maxville Limestone:1) ~4 to 5 feet of fissile black shale with smooth, slightly shiny concretions (paleopebbles?)2) Sharon Conglomerate - quartz-pebble conglomerate3) Black shale4) Gray, non-fissile claystone with lumpy iron oxide concretions5) Unconformity with minor paleotopography6) Maxville Limestone - mostly lime mudstone (micritic limestone) with occasional lenses or pockets of fossil shell hash; some thin shale interbeds; one small apparent sandstone lens (= relatively thin, gray, clay-rich interval with sandy-silty grains); occasional coarsely-crystalline/coarse-grained limestone intervals with finely laminated argillaceous limestone; some slickenlined surfaces seen in the incompetent clay-rich intervals. Observed fossils include brachiopods (Composita subquadrata atrypids), bivalves, gastropods (Straparollus planodorsatus and Bellerophon sublaevis), and crinoids (even calyx material). Straparollus gastropods are common in the argillaceous intervals - they are compacted and compressed. One Straparollus fossil snail was seen with a healed shell fracture/break.Notable Pennsylvanian float samples in the section: a Lepidodendron tree trunk with nice, diamond-shaped leaf scars and a coarse-grained rip-up clast breccia.The fossils shown here are compressed Straparollus planodorsatus snails (this species is also known as Straparollus similis). 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. Most marine snails are herbivores (algae grazers) or predators/carnivores. 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.Classification: Animalia, Mollusca, Gastropoda, EuomphalidaeStratigraphy: shaly limestone in the Maxville Limestone, Meramecian to Chesterian, Middle to Upper MississippianLocality: Pleasant Valley Limestone Quarry (spoils pile at the southwestern end of the quarry), southwest of Dillon Lake, Hopewell Township, western Muskingum County, eastern Ohio, USA (~vicinity of 39° 58' 49.64" North latitude, 82° 08' 05.74" West longitude)-------------------------Reference cited:Stout (1918) - Geology of Muskingum County. Geological Survey of Ohio, Fourth Series, Bulletin 21. 351 pp. |
| 撮影日 | 2018-10-03 17:22:08 |
| 撮影者 | James St. John |
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