Last updated Stromatoporoid at Fisk Quarry, Isle La Motte, VermontChazy fossils (rhaphanocrinus gemmeus), New York State Museum, 1902
The Chazy Reef Formation is a mid-Ordovician limestone deposit in northeastern North America.
The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago (Mya) to the start of the Silurian Period 443.8 Mya.
North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere; it is also considered by some to be a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.
It consists of some of the oldest reef systems built by a community of organisms[1] rather than the deposit of a limited range of similar organisms, such as Stromatolite mounds deposited by ancient cyanobacteria. The reef structure was formed largely by cryptostome and trepostome bryozoa, some of the oldest known bryozoans, but corals made an early appearance, and stromatoporoids.
A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Many reefs result from abiotic processes, but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae.
Stromatolites or stromatoliths are layered mounds, columns, and sheet-like sedimentary rocks that were originally formed by the growth of layer upon layer of cyanobacteria, a single-celled photosynthesizing microbe. Fossilized stromatolites provide records of ancient life on Earth. Lichen stromatolites are a proposed mechanism of formation of some kinds of layered rock structure that are formed above water, where rock meets air, by repeated colonization of the rock by endolithic lichens.
Bryozoa are a phylum of aquatic invertebrate animals. Typically about 0.5 millimetres (0.020 in) long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia. Most marine species live in tropical waters, but a few occur in oceanic trenches, and others are found in polar waters. One class lives only in a variety of freshwater environments, and a few members of a mostly marine class prefer brackish water. Over 4,000 living species are known. One genus is solitary and the rest are colonial.
The formation is named for the small town of Chazy, New York, where the reef was noted by James Hall in Palaeontology of New York (vol. I, 1847) and the fossils first studied by the Canadian paleontologist Elkanah Billings (1858, 1859).[2] The reef extends from Tennessee to Quebec[3] and Newfoundland, but its most easily studied outcropping is at Goodsell Ridge, Isle La Motte, the northernmost island in Lake Champlain; there, gentle uplift has tilted the sediments: the bedding planes now dip slightly to the north, revealing sequences of horizons in exposed rock. The black limestone of Isle La Motte takes a polish, revealing the white "bird's-eye"[4] markings of embedded fossil shells, notably the spirals formed by sliced gastropod shells. Rock of the Chazy Formation was quarried from the nineteenth century at the Fisk Quarry, Isle La Motte, the oldest quarry in Vermont.[5] Portions of the exposed reef on several islands in Lake Champlain were dedicated as the Chazy Fossil ReefNational Natural Landmark in 2009.[6]
Chazy is a town in northeastern Clinton County, New York, in the United States. The population was 4,284 at the 2010 census. The closest city is Plattsburgh, 14 miles (23 km) to the south. Chazy is 8 miles (13 km) south of the Canada–United States border. The ZIP code is 12921 and it is in area code 518.
Elkanah Billings is often referred to as Canada's first paleontologist. Billings was born on a farm by the Rideau River outside Bytown (Ottawa), now known as Billings Estate. His parents were named Lamira and Braddish Billings. His family included an older sister named Sabra and an older brother Maj Braddish Billings Jr, who practised as an architect and served in the North-West Rebellion. His brother W. Ross Billings also practised as an architect. His younger siblings were Samuel, Sarah and Charles. He was originally educated in law and in 1845, he was called to the Canadian bar. In 1852, he founded the journal the Canadian Naturalist . He continued to practise law until 1856, when he was hired to be the first paleontologist for Geological Survey of Canada (GSC). In his lifetime, he identified 1065 new species and 61 new genera, including Aspidella, the first documented fossil of the Ediacaran biota.
Tennessee is a state located in the southeastern region of the United States. Tennessee is the 36th largest and the 16th most populous of the 50 United States. Tennessee is bordered by Kentucky to the north, Virginia to the northeast, North Carolina to the east, Georgia, Alabama, and Mississippi to the south, Arkansas to the west, and Missouri to the northwest. The Appalachian Mountains dominate the eastern part of the state, and the Mississippi River forms the state's western border. Nashville is the state's capital and largest city, with a 2017 population of 667,560. Tennessee's second largest city is Memphis, which had a population of 652,236 in 2017.
The system formed in warm tropical waters of the Iapetus Ocean, in low latitudes of the Southern Hemisphere. The site was in shallow waters of a continental shelf: the continental craton of Laurentia lay to the west, beyond the lagoon system that formed behind the protective reef. The time was some 480-450Ma (million years ago), at a period when global paleoclimate was so warm that the planet was all but ice-free. Atmospheric carbon dioxide was fourteen to sixteen times more plentiful than it is today.
The Iapetus Ocean was an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale. The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia. The ocean disappeared with the Acadian, Caledonian and Taconic orogenies, when these three continents joined to form one big landmass called Euramerica. The "southern" Iapetus Ocean has been proposed to have closed with the Famatinian and Taconic orogenies, meaning a collision between Western Gondwana and Laurentia.
The Southern Hemisphere is the half of Earth that is south of the Equator. It contains all or parts of five continents, four oceans and most of the Pacific Islands in Oceania. Its surface is 80.9% water, compared with 60.7% water in the case of the Northern Hemisphere, and it contains 32.7% of Earth's land.
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water known as a shelf sea. Much of the shelves were exposed during glacial periods and interglacial periods.
The Chazy Reef Formation, which built up vertically from a muddy base catching fine dark silt as it grew, began as mounds deposited by bryozoans that stabilized a muddy bottom, then built up into the water column to such an extent that the connected mounds modified their surrounding environment (Mehrtens). As the reef aged, it began to offer an increasing variety of ecological niches, which fostered the first rich local biodiversity that has characterized all reef systems ever since. One dominant reef-building organism took the place of another, in a slowly evolving faunal succession.
Biodiversity refers to the variety and variability of life on Earth. Biodiversity typically measures variation at the genetic, species, and ecosystem level. Terrestrial biodiversity is usually greater near the equator, which is the result of the warm climate and high primary productivity. Biodiversity is not distributed evenly on Earth, and is richest in the tropics. These tropical forest ecosystems cover less than 10 percent of earth's surface, and contain about 90 percent of the world's species. Marine biodiversity is usually highest along coasts in the Western Pacific, where sea surface temperature is highest, and in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time, but will be likely to slow in the future.
The Chazy Reef Formation has given its name to the contemporaneous mid-Ordovician faunal stage, the Chazyan.
Notes
↑ P.E. Raymond of Harvard called it “the oldest coral reef in the world” (Raymond 1924), though coral rubble was not in fact the primary reef building material.
↑ Percy E. Raymond, "The Trilobites of the Chazy Limestone", Annals of the Carenegie Museum3.2 (1905): "...the forty years which have elapsed since the distinguished Canadian paleontologist, Elkanah Billings, published his descriptions of Chazy fossils".
Raymond, P.E. 1924. "The oldest coral reef" Report of the Vermont State Geologist, no. 14, pp 72–77.
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