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Paha Sapa Limestone
The Pahasapa Formation is a geological unit of primarily limestone and dolomite that is exposed in the Black Hills of South Dakota and northeastern Wyoming, and underlies parts of Nebraska, in the United States. Also referred to as the Pahasapa Limestone (especially in older publications and outside South Dakota), this unit is analogous to the Madison Limestone, the Lodgepole Limestone, and the Burlington Limestone, other Mississippian-aged limestones and dolomites in the midwestern United States. Some recent literature has grouped stretches of the Pahasapa into the Madison Group. The formation is of local importance, as it contains the Madison aquifer, and two of the ten longest caves in the world. Lithology The Pahasapa consists mainly of grey massive limestone and dolomite. The limestone has been classified as primary dolo-sparitic, with some micrite, using the Folk classification, and as skeletal wackestone using the Dunham classification. The central Black Hills Pahasapa is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formation (stratigraphy)
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness (geology), thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crinoid
Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths as great as . Adult crinoids are characterised by having the mouth located on the upper surface. This is surrounded by feeding arms, and is linked to a U-shaped gut, with the anus being located on the oral disc near the mouth. Although the basic echinoderm pattern of fivefold symmetry can be recognised, in most crinoids the five arms are subdivided into ten or more. These have feathery pinnules and are spread wide to gather planktonic particles from the water. At some stage in their lives, most crinoids have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleontology In South Dakota
Paleontology in South Dakota refers to paleontological research occurring within or conducted by people from the U.S. state of South Dakota. South Dakota is an excellent source of fossils as finds have been widespread throughout the state. During the early Paleozoic era South Dakota was submerged by a shallow sea that would come to be home to creatures like brachiopods, cephalopods, corals, and ostracoderms. Local sea levels rose and fall during the Carboniferous and the sea left completely during the Permian. During the Triassic, the state became a coastal plain, but by the Jurassic it was under a sea where ammonites lived. Cretaceous South Dakota was also covered by a sea that was home to mosasaurs. The sea remained in place after the start of the Cenozoic before giving way to a terrestrial mammal fauna including the camel ''Poebrotherium'', three-toed horses, rhinoceroses, saber-toothed cat, and titanotheres. During the Ice Age glaciers entered the state, which was home to mammot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Fossiliferous Stratigraphic Units In South Dakota
This article contains a list of fossil-bearing stratigraphic units in the state of South Dakota, U.S. Sites See also * Paleontology in South Dakota References * {{DEFAULTSORT:Fossiliferous stratigraphic units in South Dakota South Dakota Stratigraphic units A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize ... Stratigraphy of South Dakota South Dakota geography-related lists United States geology-related lists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speleothem
A speleothem (; ) is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful paleoclimatic proxies. Chemical and physical characteristics More than 300 variations of cave mineral deposits have been identified. The vast majority of speleothems are calcareous, composed of calcium carbonate (CaCO3) minerals (calcite or aragonite). Less commonly, speleothems are made of calcium sulfate (gypsum or mirabilite) or opal. Speleothems of pure calcium carbonate or calcium sulfate are translucent and colorless. The presence of iron oxide or copper provides a reddish brown color. The presence of manganese oxide can create darker colors such as black or dark brown. Speleothems can also be brown d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jewel Cave National Monument
Jewel Cave National Monument contains Jewel Cave, currently the third longest cave in the world, with of mapped passageways. It is located approximately west of the town of Custer in Black Hills of South Dakota. It became a national monument in 1908. History Frank and Albert Michaud, two local prospectors, discovered the cave in 1900, when they felt cold air blowing out of a small hole in a canyon. It is unknown whether any previous inhabitants of the area were aware of the natural cave opening, which was not large enough for a person to enter.Jewel Cave brochure; National Park Service; GPO, WDC After enlarging the cave entrance with dynamite, the Michaud brothers found a cavern lined with calcite crystals, which led them to name it "Jewel Cave". The brothers tried to capitalize on the discovery, widening the opening, building walkways inside, and opening it to tourists. Although their venture was unsuccessful, news of the discovery eventually reached Washington. President Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Speleological Society
The National Speleological Society (NSS) is an organization formed in 1941 to advance the exploration, conservation, study, and understanding of caves in the United States. Originally headquartered in Washington D.C., its current offices are in Huntsville, Alabama. The organization engages in the research and scientific study, restoration, exploration, and protection of caves. It has more than 10,000 members in more than 250 grottos. History The Speleological Society of the District of Columbia (SSDC) was formed on May 6, 1939 by Bill Stephenson. In the fall of 1940, the officers of the SSDC drafted a proposed constitution that would transform the SSDC into the National Speleological Society. On January 24, 1941, Stephenson sent a letter to all members of the SSDC announcing that "on January 1 the Society was reorganized as a national organization." The New England Grotto was the first NSS Grotto. It was chartered in 1941 with Clay Perry as president and Ned Anderson as vice pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wind Cave National Park
Wind Cave National Park is an American national park located north of the town of Hot Springs in western South Dakota. Established on January 3, 1903 by President Theodore Roosevelt, it was the sixth national park in the U.S. and the first cave to be designated a national park anywhere in the world. The cave is notable for its calcite formations known as boxwork, as well as its frostwork. Approximately 95 percent of the world's discovered boxwork formations are found in Wind Cave. The cave is recognized as the densest cave system in the world, with the greatest passage volume per cubic mile. Wind Cave is the seventh longest cave in the world with of explored cave passageways () and the third longest cave in the United States. Above ground, the park includes the largest remaining natural mixed-grass prairie in the United States. Origin of name The passages in the park are said to "breathe" as air continually moves into or out of them, equalizing the atmospheric pressure of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dolomitized
Dolomitization is a geological process by which the carbonate mineral dolomite is formed when magnesium ions replace calcium ions in another carbonate mineral, calcite. It is common for this mineral alteration into dolomite to take place due to evaporation of water in the sabkha area. Dolomitization involves substantial amount of recrystallization. This process is described by the stoichiometric equation: :2 CaCO3(calcite) + Mg2+ ↔ CaMg(CO3)2(dolomite) + Ca2+ Dolomitization depends on specific conditions which include low Ca:Mg ratio in solution, reactant surface area, the mineralogy of the reactant, high temperatures which represents the thermodynamic stability of the system, and the presence of kinetic inhibitors such as sulfate. If the kinetic inhibitors and high temperatures are compatible, then dolomitization can take place in saline environments above thermodynamic and kinetic saturation with respect to dolomite. This type of environment includes, freshwater and seawat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentremites
''Pentremites'' is an extinct genus of blastoid echinoderm belonging to the family Pentremitidae. Description These stalked echinoderms averaged a height of about but occasionally ranged up to about 3 times that size. They, like other blastoids, superficially resemble their distant relatives, the crinoids or ''sea lilies'', having a near-identical, planktivore, planktivorous lifestyle living on the sea floor attached by a stalk. As with all other blastoids, species of ''Pentremites'' trapped food floating in the currents by means of tentacle-like appendages. ''Pentremites'' species lived in the early to middle Carboniferous, from 360.7 to 314.6 Ma. Its fossils are known from North America. References * ''Fossils'' (Smithsonian Handbooks) by David Ward (paleontologist), David Ward (Page 190) Blastozoa genera Carboniferous echinoderms of North America Fossils of Georgia (U.S. state) Paleozoic life of Alberta Paleozoic life of the Northwest Territories Paleozoic life of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euomphalus
''Euomphalus'' is a genus of fossil marine gastropods known to have lived from the Silurian to the Middle Permian.J.B.Knight,et al 1960. Treatise on Invertebrate Paleontology, Part I, Mollusca 1, ch on systematic descriptions. Geol Soc of America and Univ Kansas Press.(in Czech) Pek I., Vašíček Z., Roček Z., Hajn. V. & Mikuláš R.: ''Základy zoopaleontologie''. - Olomouc, 1996. 264 pp., . Description ''Euomphalus'' is characterized by a closely coiled shell with a depressed to slightly elevated spire and a channel-bearing angulation (a selenizone) on the upper surface of the whorls. The lower surface of the whorls is rounded to angular. ''Amphiscapha'', '' Philoxene'', and '' Straparollus'' are among similar related genera. '' Serpulospira'', also related, differs in having a broadly open spiral in the adult form. Taxonomy ''Euomphalus'' is the type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the famil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bellerophon (genus)
''Bellerophon'' is a genus of extinct paleozoic marine molluscs of uncertain position (Gastropoda or Monoplacophora) in the family Bellerophontidae. The genus was named after Bellerophon, the ancient Greek hero. ''Bellerophon'' is the type genus of the family Bellerophontidae. Shell description The genus is characterised by a shell which is globose, convolute, and planispiral (symmetrically coiled). The shell of ''Bellerophon'' superficially resembles that of a miniature cephalopod (e.g. ''Nautilus'' or an ammonite), except that septa are lacking. The shell of ''Bellerophon'' is often a couple of centimeters in maximum dimension. The external surface is smooth, ornamented only by growth lines. There is a low crest or ridge running along the midline of the shell. Many specimens of ''Bellerophon'' show something resembling a "waterline" about halfway up the shell, suggesting that a large amount of the mantle and foot were exposed and covered the outside of the shell, as in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
