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Chepultepec Formation
The Chepultepec Formation, is an Early Ordovician-age geological formation in the Appalachian regions of Eastern North America. Also known as the Chepultepec Dolomite, it is a unit of the Upper Knox Group, overlying the Copper Ridge Dolomite and underlying the Longview- Kingsport-Mascot sequence. The Chepultepec Formation is a primarily limestone and dolomite formation, the earliest formation of the Ordovician period in its area. Further north, it is equivalent to the Stonehenge Formation of the Beekmantown Group. The formation was first described from Allgood, Alabama, and has also been found in Tennessee and Virginia. Allgood was originally named "Chepultepec", providing its name to the formation as well. In Virginia, the Chepultepec Formation has a habit of forming large natural arches, including Natural Tunnel in Scott County and Natural Bridge in Rockbridge County. See also * List of fossiliferous stratigraphic units in Virginia * Paleontology in Virginia * Carbonate-ho ... [...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] |
Dolomite (rock)
Dolomite (also known as dolomite rock, dolostone or dolomitic rock) is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite, CaMg(CO3)2. It occurs widely, often in association with limestone and evaporites, though it is less abundant than limestone and rare in Cenozoic rock beds (beds less than about 66 million years in age). The first geologist to distinguish dolomite rock from limestone was Belsazar Hacquet in 1778. Most dolomite was formed as a magnesium replacement of limestone or of lime mud before lithification. The geological process of conversion of calcite to dolomite is known as dolomitization and any intermediate product is known as dolomitic limestone. The "dolomite problem" refers to the vast worldwide depositions of dolomite in the past geologic record in contrast to the limited amounts of dolomite formed in modern times. Recent research has revealed sulfate-reducing bacteria living in anoxic conditions precipitate dolomite which ind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician Geology Of Tennessee
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian Perio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonate-hosted Lead-zinc Ore Deposits
Carbonate-hosted lead-zinc ore deposits are important and highly valuable concentrations of lead and zinc sulfide ores hosted within carbonate (limestone, marl, dolomite) formations and which share a common genetic origin. These ore bodies range from 0.5 million tonnes of contained ore, to 20 million tonnes or more, and have a grade of between 4% combined lead and zinc to over 14% combined lead and zinc. These ore bodies tend to be compact, fairly uniform plug-like or pipe-like replacements of their host carbonate sequences and as such can be extremely profitable mines. This classification of ore deposits is also known as Mississippi Valley Type or ''MVT'' ore deposits, after a number of such deposits along the Mississippi River in the United States, where such ores were first recognised; these include the famed Southeast Missouri Lead District of southeastern Missouri, and deposits in northeast Iowa, southwest Wisconsin, and northwest Illinois. Similarly Irish-type carbonat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleontology In Virginia
Paleontology in Virginia refers to paleontological research occurring within or conducted by people from the U.S. state of Virginia. The geologic column in Virginia spans from the Cambrian to the Quaternary. During the early part of the Paleozoic, Virginia was covered by a warm shallow sea. This sea would come to be inhabited by creatures like brachiopods, bryozoans, corals, and nautiloids. The state was briefly out of the sea during the Ordovician, but by the Silurian it was once again submerged. During this second period of inundation the state was home to brachiopods, trilobites and entire reef systems. During the mid-to-late Carboniferous the state gradually became a swampy environment. During the Triassic, the state was covered vegetated by horsetails and trees. Dinosaurs roamed the area, leaving behind both bones and footprints. Many fishes from local lakes were preserved during the Jurassic. Virginia was covered by seawater again during the Cretaceous, when belemnites a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Fossiliferous Stratigraphic Units In Virginia
This article contains a list of fossil-bearing stratigraphic units in the state of Virginia, U.S. Sites See also * Paleontology in Virginia References * {{DEFAULTSORT:Fossiliferous stratigraphic units in Virginia Virginia 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 Virginia Virginia geography-related lists United States geology-related lists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rockbridge County, Virginia
Rockbridge County is a county in the Shenandoah Valley on the western edge of the Commonwealth of Virginia. As of the 2020 census, the population was 22,650. Its county seat is the city of Lexington. Rockbridge County completely surrounds the independent cities of Buena Vista and Lexington. The Bureau of Economic Analysis combines the independent cities of Buena Vista and Lexington with Rockbridge County for statistical purposes. History Rockbridge County was established in October 1777, from parts of now neighboring Augusta and Botetourt counties, and the first county elections were held in May 1778. Rockbridge County was named for Natural Bridge, a notable landmark in the southern portion of the county. Rockbridge County was formed during an act of assembly intended to reduce the amount of travel to the nearest courthouse, and to ensure trials were held fairly, and among friends rather than strangers. The first court session in Rockbridge County was held at the home of S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Bridge (Virginia)
Natural Bridge is a geological formation in Rockbridge County, Virginia, comprising a natural arch with a span of . It is situated within a gorge carved from the surrounding mountainous limestone terrain by Cedar Creek, a small tributary of the James River. Consisting of horizontal limestone strata, Natural Bridge is the remains of the roof of a cave or tunnel through which the Cedar Creek once flowed. Natural Bridge has been designated a Virginia Historic Landmark and a National Historic Landmark. Since 2016, the bridge and its surroundings have been managed by the Commonwealth of Virginia as Natural Bridge State Park. Geology Rocks in the area are limestones and dolomites from the Ordovician Period, which implies deposition about 470 million years ago. The carbonates of the Natural Bridge occur within the Chepultepec Formation, making the buttress of the bridge, and the Beekmantown Formation, deposited conformably over the Chepultepec and comprising the span and the uppe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scott County, Virginia
Scott County is a county located in the southwestern part of the U.S. state of Virginia. As of the 2020 census, the population was 21,576. Its county seat is Gate City. Scott County was formed by an act of the General Assembly on November 24, 1814, from parts of Washington, Lee, and Russell Counties and was named for Virginia born General Winfield Scott. Scott County is part of the Kingsport–Bristol–Bristol, TN-VA Metropolitan Statistical Area, which is a component of the Johnson City–Kingsport–Bristol, TN-VA Combined Statistical Area, commonly known as the " Tri-Cities" region. The County Administrator is Freda Russell Starnes. History The early settlers found evidence of a former native village at the mouth of Stony Creek on the Clinch river. Thomas McCulloch was the first white settler within the county, in 1769. Daniel Boone commanded several forts located here in 1774 during Dunmore's War, and several more were built in successive years. Even so, the Chickamau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Tunnel State Park
Natural Tunnel State Park is a Virginia state park, centered on the Natural Tunnel, a massive naturally formed cave that is so large it is used as a railroad tunnel. It is located in the Appalachian Mountains near Duffield in Scott County, Virginia. The Natural Tunnel, which is up to wide and high, began to form more than a million years ago when groundwater bearing carbonic acid percolated through crevices and slowly dissolved limestone and dolomite bedrock. A small river, which is now called Stock Creek, was diverted underground and it continued to erode the tunnel over many millennia. The walls of the tunnel show evidence of prehistoric life. Many fossils have been found in the creek bed and in the tunnel walls. Geology The tunnel passes through Purchase Ridge, which is made of the Ordovician Chepultepec Limestone and is near the axis of the Purchase Ridge syncline. It lies between the Clinchport Thrust Fault and the Hunter Valley Thrust Fault, on the Hunter Valley Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arch
An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it. Arches may be synonymous with vaults, but a vault may be distinguished as a continuous arch forming a roof. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture, and their systematic use started with the ancient Romans, who were the first to apply the technique to a wide range of structures. Basic concepts An arch is a pure compression form. It can span a large area by resolving forces into compressive stresses, and thereby eliminating tensile stresses. This is sometimes denominated "arch action". As the forces in the arch are transferred to its base, the arch pushes outward at its base, denominated "thrust". As the rise, i. e. height, of the arch decreases the outward thrust increases. In order to preserve arch action and prevent collapse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allgood, Alabama
Allgood, formerly known as Chepultepec, is a town in Blount County, Alabama, United States. At the 2020 census, the population was 548. History One source said the town's name comes from a family of homesteaders from South Carolina who settled in the area in the early 19th century. However, another states that the original name of the village, Chepultepec, probably named for the Battle of Chapultepec in the Mexican–American War, was changed to "Allgood" in December 1915. A local lime manufacturer believed he was not getting repeat business because of the difficulty in spelling the name of the village and persuaded the local postmaster to change the name, with the postmaster giving the village his own name of Allgood. The town was formally incorporated in 1959. In 2010, it became the first locality in Alabama to achieve a Hispanic plurality. Geography Allgood is located in south-central Blount County at (33.904216, −86.516428). It is in the Murphree Valley, with Straight Moun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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