Bethel Shale Member (wall of Great Onyx Cave, Flint Ridge, Mammoth Cave National Park, Kentucky, USA) 1 : 無料・フリー素材/写真
Bethel Shale Member (wall of Great Onyx Cave, Flint Ridge, Mammoth Cave National Park, Kentucky, 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 | Bethel Shale Member exposed in the wall of Great Onyx Cave.Great Onyx Cave is located in the northern part of Flint Ridge in Mammoth Cave National Park, Kentucky, USA. It has 8 miles worth of mapped passages. Geologically, Great Onyx Cave is part of the Mammoth Cave System, but it has become erosively separated from it (although an air flow connection with the Mammoth Cave System has been identified). Great Onyx Cave is the downstream continuation of the Salt Cave section of the system.The walls of Great Onyx Cave are limestones of the Paoli Member, shales of the Bethel Member, and limestones of the Beaver Bend Member of the Girkin Formation (lower Upper Mississippian). The travertine speleothem-rich areas of Great Onyx Cave are wet and occur where a cap of overlying Big Clifty Sandstone is absent. The dry portions of the cave are below an intact Big Clifty Sandstone "caprock", and include the giant canyon passage areas and the gypsum speleothem areas.The main cave passage of Great Onyx Cave is called Edwards Avenue, developed at Level B in the Mammoth Cave System. Level B passages formed about 2 to 4 million years ago during the Pliocene. Edwards Avenue is a giant canyon passage. Canyon passages are tall and narrow, and form in the vadose zone (above the water table). Giant canyon passages (a.k.a. rectangular passages) are much larger and can form in either the vadose or phreatic zone (at or below the water table). They are usually more than half-way filled with sediments and breakdown. Famous examples of giant canyon passages in Mammoth Cave park include Main Cave, Audubon Avenue, Broadway Avenue, and Sandstone Avenue.This cave is sometimes accessible to the general public by guided lantern tours during boreal summer months. This photo was taken during a field trip in June 2011 as part of a cave geology course at Mammoth Cave park.The above photo shows some travertine speleothem (stalactites and coralloids) attached to the ceiling. The rock wall at the bottom of the picture is limestone of the uppermost Paoli Member (Girkin Formation). The grayish-colored, recessed area above that is the entire Bethel Shale Member (also part of the Girkin Formation). The ceiling here is limestone of the basal Beaver Bend Member of the Girkin Formation. |
| 撮影日 | 2011-06-16 15:02:25 |
| 撮影者 | James St. John |
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