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Tremadocian
The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from to million years ago. The base of the Tremadocian is defined as the First appearance datum, first appearance of the conodont species ''Iapetognathus fluctivagus'' at the Global Boundary Stratotype Section and Point (GSSP) section on Newfoundland (island), Newfoundland. Naming The Tremadocian is named after the village Tremadog, Tremadoc in Wales. The name was proposed by Adam Sedgwick in 1846 (as "Tremadoc group"). GSSP The GSSP for the beginning of the Tremadocian is the Green Point section () in Gros Morne National Park, in western Newfoundland (island), Newfoundland. It is defined as the First appearance datum, first appearance of the conodont species ''Iapetognathus fluctivagus''. This horizon can be found 101.8 m above the Greenpoint section datum within bed number 23. The boundary lies within the Broom Point Member, of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Ordovician
The Early Ordovician is the first epoch of the Ordovician period, corresponding to the Lower Ordovician series of the Ordovician system. It began after the Age 10 of the Furongian epoch of the Cambrian and lasted from to million years ago, until the Dapingian age of the Middle Ordovician. It includes Tremadocian and Floian ages. History International Commission on Stratigraphy (ICS) appointed working groups on the boundaries of the Ordovician subdivisions in 1974. The boundaries were established by the fauna of conodonts and/or graptolites. In 1995, the Subcommission on Ordovician Stratigraphy, with the support of 90% majority of voting members, adopted the division of the Ordovician system into three series: Lower, Middle and Upper. In the same year, it was decided to divide each of the three series into two global stages. ''Tetragraptus approximatus'' zone was chosen as the base of the upper stage of the Lower Ordovician by 95% of the votes. Before the adoption of the in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iapetognathus Fluctivagus
''Iapetognathus fluctivagus'' is a species of denticulate cordylodan conodonts belonging to the genus '' Iapetognathus''. It existed during the Tremadocian Age ( million years ago) of the Ordovician. It is an important index fossil in biostratigraphy. Description Like other members of the genus, ''Iapetognathus fluctivagus'' had ramiform (branching) array of elements (apparatus). It is believed that the ramiform apparatus in ''Iapetognathus fluctivagus'' evolved from the coniform (cone-like) apparatus of '' Iapetonudus ibexensis''. It can be readily distinguished from other conodonts existing during the same age by the sideward orientation of the major teeth-like projections (denticulate processes). Taxonomy ''Iapetognathus fluctivagus'' is classified under the genus '' Iapetognathus''. It belongs to the cordylodan family Cordylodontidae of the order Proconodontida (Cavidonti). It was first described in 1999 by paleontologists Robert S. Nicoll, James F. Miller, Godfrey S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period Megaannum, Ma (million years ago) to the start of the Silurian Period Ma. The Ordovician, named after the Celtic Britons, 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 (geology), rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed Stratum, 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 per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Floian
The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician series. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The lower boundary is defined as the first appearance of the graptolite species '' Tetragraptus approximatus''. History and naming The base of this stage was ratified by the International Commission on Stratigraphy (ICS) in 2002. The Floian Stage is named after Flo, a village in Västergötland, southern Sweden. The name "Floan" was proposed in 2004, but the ICS adapted Floian as the official name of the stage. GSSP The GSSP of the Floian is the lower Tøyen Shale in Diabasbrottet Quarry () which is an outcrop of a shale-dominated stratigraphic succession. The lower boundary of the Floian is defined as the first appearance of '' Tetragraptus approximatus'' which is about 2.1 above the Cambrian strata. Radiometric dating has set the Tremad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tremadog
Tremadog (formerly Tremadoc) is a village in the Community (Wales), community of Porthmadog, in Gwynedd, north west Wales; about north of Porthmadog town centre. It was a urban planning, planned settlement, founded by William Madocks, who bought the land in 1798. The centre of Tremadog was complete by 1811 and remains substantially unaltered. Tremadog hosted an unofficial National Eisteddfod event in 1872. Planning By mid-1805, Madocks had already built some houses on the site of Tremadog, for he wrote to the Post-Master at Caernarfon informing him that letters addressed to Pentre-Gwaelod should be delivered to the new houses he had built on Traeth Mawr, near Tan-yr-Allt. Pentre-Gwaelod translates as Bottom Village, but Madocks had grander plans, for aldermen and a mayor had been appointed, and he corrected the word "village" in a letter written soon afterward to read "borough". He planned it himself, perhaps with some help from architectural friends and architectural bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gros Morne National Park
Gros Morne National Park is a Canadian national park and World Heritage Site located on the west coast of Newfoundland. At , it is the second largest national park in Atlantic Canada after Torngat Mountains National Park, which has an area of . The park takes its name from Newfoundland's second-highest mountain peak (at ) located within the park. Its French meaning is "large mountain standing alone," or more literally "great sombre." Gros Morne is a member of the Long Range Mountains, an outlying range of the Appalachian Mountains, stretching the length of the island's west coast. It is the eroded remnants of a mountain range formed 1.2 billion years ago. In 1987, the park was awarded World Heritage Site status by UNESCO because "The park provides a rare example of the process of continental drift, where deep ocean crust and the rocks of the earth's mantle lie exposed." The Gros Morne National Park Reserve was established in 1973, and was made a national park on Octo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Boundary Stratotype Section And Point
A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted by the International Commission on Stratigraphy, a part of the International Union of Geological Sciences. Most, but not all, GSSPs are based on paleontological changes. Hence GSSPs are usually described in terms of transitions between different faunal stages, though far more faunal stages have been described than GSSPs. The GSSP definition effort commenced in 1977. As of 2024, 79 of the 101 stages that need a GSSP have a ratified GSSP. Rules A geologic section has to fulfill a set of criteria to be adapted as a GSSP by the ICS. The following list summarizes the criteria: * A GSSP has to define the lower boundary of a geologic stage. * The lower boundary has to be defined using a primary mar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Green Point, Newfoundland
Green Point is located 12 km north of the town of Rocky Harbour in Gros Morne National Park,Gros Morne National Park: Visitor information (2007) Retrieved August 18, 2008 from http://www.pc.gc.ca/pn-np/nl/grosmorne/visit/visit4_e.asp#04 on the west coast of Newfoundland (island), Newfoundland. It is the home to a small summer fishing community and a drive-in campground. In 2000, Green Point was designated the Global Boundary Stratotype Section and Point, Global Stratotype Section and Point (GSSP) representing the division between the Cambrian and the Ordovician systems.Cooper, R. A., Nowlan, G. S., and Williams, S. H. (2001). Global Stratotype Section and Point for Base of the Ordovician System. ''Episodes'', 24(1). Retrieved August 18, 2008, from http://www.stratigraphy.org/Tremadocian.pdf Geology In 2000, the cliffs at Green Point were approved as the Global Stratotype Section and Point for the base of the Ordovician system by the International Union of Geological Sciences. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
First Appearance Datum
First appearance datum (FAD) is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. FADs are determined by identifying the geologically oldest fossil discovered, to date, of a particular species. A related term is last appearance datum (LAD), the last appearance of a species in the geologic record. FADs are frequently used to designate segments in the geologic time scale. A given FAD can be used to define a Global Boundary Stratotype Section and Point (GSSP). For example, the beginning of the Tremadocian Stage of the Ordovician Period is marked by the first appearance of the conodont ''Iapetognathus fluctivagus'' in the geologic record. This occurs in bed 23 of the rock formation known as the Green Point section, located in western Newfoundland, as well as in geologically correlated strata in many parts of the world. However, diachronous FADs can be problematic for correlating chronostratigraphic units, particular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Green Point Formation
The Green Point Formation is a geologic formation in Newfoundland and Labrador. It preserves fossils dating back to the Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ... period. See also * List of fossiliferous stratigraphic units in Newfoundland and Labrador References * Ordovician Newfoundland and Labrador Cambrian southern paleotemperate deposits Ordovician southern paleotemperate deposits Geologic formations of Newfoundland and Labrador Limestone formations of Canada Shale formations of Canada Conglomerate formations of Canada Siltstone formations of Canada Chert formations {{Newfoundland-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Commission On Stratigraphy
The International Commission on Stratigraphy (ICS), sometimes unofficially referred to as the International Stratigraphic Commission, is a daughter or major subcommittee grade scientific organization that concerns itself with stratigraphy, stratigraphical, geology, geological, and chronology, geochronological matters, worldwide. It is the largest subordinate body of the International Union of Geological Sciences (IUGS). The ICS is essentially a permanent working committee, working subcommittee, which meets far more regularly than the quadrennial meetings scheduled by the IUGS, when it meets as a congress or committee, membership of the whole. Aims One of its main aims, a project begun in 1974, is to establish a multidisciplinary standard and global geologic time scale that will ease paleontology, paleontological and geobiology, geobiological comparisons region to region by benchmarks with stringent and rigorous strata criteria called Global Boundary Stratotype Section and Points ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
