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Academic literature on the topic 'Ordovician age'

Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

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Journal articles on the topic "Ordovician age"

1

Sun, Weidong. "The age of the Ordovician-Silurian boundary and the End Ordovician Mass Extinction." Solid Earth Sciences 4, no. 4 (December 2019): 199–200. http://dx.doi.org/10.1016/j.sesci.2019.11.007.

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Sun, Weidong. "The age of the Ordovician-Silurian boundary and the End Ordovician Mass Extinction." Solid Earth Sciences 5, no. 1 (March 2020): 29–30. http://dx.doi.org/10.1016/j.sesci.2019.11.008.

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3

Smith, M. P., and J. S. Peel. "The age of the Danmarks Fjord Member, eastern North Greenland." Rapport Grønlands Geologiske Undersøgelse 132 (December 31, 1986): 7–13. http://dx.doi.org/10.34194/rapggu.v132.7957.

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Conodonts of late Early Ordovician age (late Canadian, early-middle Arenigian) are identified from the Danmarks Fjord Member of the Wandel Valley Formation at its type locality near the head of Danmark Fjord, eastern North Greenland. The identifications confirm recent suggestions of an Early Ordovician age for the member made on lithostratigraphic grounds, and refute earlier opinions that the dolomite was probably of Early Cambrian age.

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Wynne, P. Jane, E. Irving, Daniel J. Schulze, Douglas C. Hall, and Hewart H. Helmstaedt. "Paleomagnetism and age of three Canadian Rocky Mountain diatremes." Canadian Journal of Earth Sciences 29, no. 1 (January 1, 1992): 35–47. http://dx.doi.org/10.1139/e92-005.

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Paleomagnetic results, and age estimates derived from them, arc presented for three diatremes, using as a basis of comparison the combined apparent polar wander (APW) path for North America and Europe of Van der Voo. The Cross diatreme of the Front Ranges of the Canadian Rocky Mountains has yielded a radiometric age of 241 Ma (earliest Triassic) and is hosted by the flat-lying Pennsylvanian Tunnel Mountain Formation. It has normal polarity magnetization and yields a paleopole correctly placed according to its radiometric age on the APW path. The Blackpool diatreme (for which no radiometric age is available), which is located in the Main Ranges of the Rocky Mountains, is known to be post-Late Ordovician because it is hosted by rocks of that age. It also has magnetization of normal polarity and yields a paleopole that, when calculated with respect to present horizontal, is coincident with the latest Cretaceous to Paleocene paleopole for North America. The paleopole, when calculated with respect to bedding, lies on the Middle Ordovician portion of the combined APW path. A clockwise rotation of 10° brings the paleopole into agreement with the latest Ordovician. Hence, from a paleomagnetic standpoint, a latest Cretaceous to Paleocene or latest Ordovician age is possible. The HP pipe (radiometric age 391 ± 5 Ma or Early Devonian), previously studied by D. T. A. Symons and M. T. Lewchuk, is hosted in limestones of Upper Cambrian to Middle Ordovician age. It has reversed polarity and yields a paleopole that, when compared with the combined APW path, suggests an age of mid-Permian, although errors are such that it could be somewhat younger, roughly coeval with the Cross diatreme. We conclude, therefore, that the radiometric age estimated for the HP pipe could be too old by about 130 million years.

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Pharaoh, T. C., T. S. Brewer, and P. C. Webb. "Subduction-related magmatism of late Ordovician age in eastern England." Geological Magazine 130, no. 5 (September 1993): 647–56. http://dx.doi.org/10.1017/s0016756800020951.

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AbstractDeep boreholes show that plutonic and volcanic igneous rocks comprise an important component of the Caledonian basement in eastern England. The isotopic compositions of these rocks reveal that many of them are of late Ordovician age (440–460 Ma), and their geochemical compositions suggest calc–alkaline affinities. The intermediate (diorite-tonalite) plutonic rocks are associated with a prominent northwest–southeast trending belt of aeromagnetic anomalies extending from Derby to St Ives, Hunts., which is interpreted to work the plutonic core of a calc-alkaline magmatic arc. It is inferred that this arc was generated by the subduction of oceanic lithosphere, possibly from the Tornquist Sea, in a south or southwest direction beneath the Midlands Microcraton in late Ordovician times. The age and geochemical composition of concealed Ordovician volcanic rocks in eastern England, and hypabyssal intrusions of the Midlands Minor Intrusive Suite in central England, is compatible with such a hypothesis.

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LOPEZ-SANCHEZ, M. A., A. IRIONDO, A. MARCOS, and F. J. MARTÍNEZ. "A U–Pb zircon age (479 ± 5 Ma) from the uppermost layers of the Ollo de Sapo Formation near Viveiro (NW Spain): implications for the duration of rifting-related Cambro-Ordovician volcanism in Iberia." Geological Magazine 152, no. 2 (August 15, 2014): 341–50. http://dx.doi.org/10.1017/s0016756814000272.

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AbstractThe uppermost metavolcanic layer of the Cambro-Ordovician Ollo de Sapo Formation, the largest accumulation of pre-Variscan igneous rocks in the Iberian Peninsula, have been dated in its northernmost part using U–Pb SHRIMP-RG zircon age techniques at 479.0 ± 4.7 Ma. The age obtained is the youngest age found so far in the metavolcanic facies of Ollo de Sapo Formation and represents the cessation of the rifting-related Cambro-Ordovician Ollo de Sapo volcanism at the northernmost tip of the Iberian Peninsula. Our results show that the Cambro-Ordovician volcanism in the NW of the Iberian Peninsula is not as short-lived as previously thought and confirm the correlation between the Cambro-Ordovician volcanic sequences that crop out in the Central Iberian Zone and the French Southern Armorican Massif. Finally, our study suggests that the cessation of the Cambro-Ordovician volcanism along the Ibero-Armorican Arc was synchronic or, less probably, slightly diachronic with younger ages towards the north (in present-day geographical coordinates).

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7

Peel, John S. "Ordovician gastropods from pebbles in Cretaceous fluvial sandstones in south-east Disko, West Greenland." Bulletin of the Geological Society of Denmark 67 (September 27, 2020): 75–81. http://dx.doi.org/10.37570/bgsd-2019-67-05.

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The gastropods Sinuopea sp. and Lecanospira cf. compacta (Salter 1859) of probable early Ordovician age are described from cherty limestone clasts within fluvial strata of the Cretaceous Atane Formation of south-east Disko, central West Greenland. The record of Sinuopea possibly suggests an earliest Ordovician (Tremadocian) age, slightly older than the Floian–Dapingian age suggested by the oldest known conodont assemblages described from West Greenland. The determinations provide supporting evidence for a former periodic cover of Ordovician strata in the Archaean terrane of south western Greenland, extending deep into the heart of the Laurentian landmass.

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Sweet, Walter C. "Conodonts and biostratigraphy of Upper Ordovician strata along a shelf to basin transect in central Nevada." Journal of Paleontology 74, no. 6 (November 2000): 1148–60. http://dx.doi.org/10.1017/s0022336000017674.

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Conodonts representing 38 species of 26 genera have been identified in samples from Upper Ordovician rocks at three central Nevada localities. Ranges of these species and associated graptolites are used graphically to determine correlation of the strata considered with an evolving composite standard that includes information from Ordovician strata at more than 100 localities in North America. Results indicate that the Hanson Creek Formation at Lone Mountain is latest Edenian through mid-Richmondian in age; that the Ordovician part of the Hanson Creek in the Monitor Range section spans an interval from Maysvillian through Richmondian; and that the upper 29 m of the Vinini Formation at the Vinini Creek locality is of mid-Maysvillian to late Richmondian age. Physical discontinuities in the Ordovician-Silurian boundary interval complicate correlations, but it is now clear that conodonts that range upward into, and have long been considered distinctive of the Lower Silurian, make their debut in central Nevada in an upper segment of the Upper Ordovician Normalograptus persculptus graptolite zone that may be latest Richmondian in age.

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Schmitz, Birger, Kenneth A. Farley, Steven Goderis, Philipp R. Heck, Stig M. Bergström, Samuele Boschi, Philippe Claeys, et al. "An extraterrestrial trigger for the mid-Ordovician ice age: Dust from the breakup of the L-chondrite parent body." Science Advances 5, no. 9 (September 2019): eaax4184. http://dx.doi.org/10.1126/sciadv.aax4184.

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The breakup of the L-chondrite parent body in the asteroid belt 466 million years (Ma) ago still delivers almost a third of all meteorites falling on Earth. Our new extraterrestrial chromite and3He data for Ordovician sediments show that the breakup took place just at the onset of a major, eustatic sea level fall previously attributed to an Ordovician ice age. Shortly after the breakup, the flux to Earth of the most fine-grained, extraterrestrial material increased by three to four orders of magnitude. In the present stratosphere, extraterrestrial dust represents 1% of all the dust and has no climatic significance. Extraordinary amounts of dust in the entire inner solar system during >2 Ma following the L-chondrite breakup cooled Earth and triggered Ordovician icehouse conditions, sea level fall, and major faunal turnovers related to the Great Ordovician Biodiversification Event.

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Molyneux, S. G., and F. Paris. "Late Ordovician Palynomorphs." Journal of Micropalaeontology 4, no. 1 (March 1, 1985): 11–26. http://dx.doi.org/10.1144/jm.4.1.11.

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Abstract. ACRITARCHSOrdovician acritarchs have been recorded in five core samples collected between 2520 ft. and 3000 ft. in Well E1-81, and ten cutting samples taken between 12150 ft. and 13240 ft. in Well J1-81A. All the assemblages recovered are of Late Ordovician age; no Early Ordovician or Middle Ordovician assemblages have been identified.Investigations have so far concentrated on the acritarch assemblages from Well El-81. The highest three Ordovician samples from depths of 2520 to 2550 ft., 2552 to 2557 ft., and 2562 to 2567 ft., yielded similar assemblages which include Veryhachium irroratum, V. cf. lairdii, V. oklahomense?, V. subglobosum, V. trispinosum, Villosacapsula setosapellicula and a new species, Striatotheca sp. A. Navifusa similis? is represented by one specimen in the sample from 2552 to 2557 ft. Another specimen from the same sample is tentatively referred to Aremoricanium syringosagis. Specimens of Baltisphaeridium, Peteinosphaeridium, Leiofusa and Eupoikilofusa occur throughout the interval 2520 to 2567 ft. but are rare. Commonly occurring species include V. irroratum and V. setosapellicula. V. irroratum has been recorded from the Middle Ordovician of North America (Loeblich & Tappan, 1969) and the Caradoc of England (Turner, 1984) but Cramer & Diez (1979) maintain that it has its acme in the Ashgill. V. setosapellicula is common in the Sylvan Shale of Oklahoma (Loeblich, 1970) which is generally understood to be of Ashgill age, but is rare in the Eden Shale (Caradoc) of Indiana (Colbath, 1979) and in the type section of the Caradoc Series in Shropshire, England (Turner, 1984). . . .

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Dissertations / Theses on the topic "Ordovician age"

1

Adiatma, Yoseph Datu. "Did early land plants produce a step-change in atmospheric oxygen centered on the Late Ordovician Sandbian Age ~458 Ma?" The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1546386257035643.

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BONJOUR, JEAN-LUC. "Sedimentation paleozoique initiale dans le domaine centre-armoricain (massif armoricain)." Rennes 1, 1988. http://www.theses.fr/1988REN10132.

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Etude des premiers depots paleozoiques reposant en discordance sur le substratum brioverien en centre armorique. Il s'agit des series rouges initiales (formation du cap de la chevre et formation de pont-rean) organises en prismes sedimentaires et se developpant en domaine continental ou a l'interface avec le domaine marin. L'evolution de la sedimentation se fait dans un cadre tectonique distensif, les niveaux volcanoclastiques interstratifies temoignant de l'instabilite de l'aire de depot. Les donnees petrographiques et geochimiques montrent que le materiel detritique provient du remaniement du brioverien sous-jacent. La couleur rouge est liee a la presente d'hematite authigene et a un phenomene diagenetique precoce. On precise l'age des series par une datation u-pb

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3

Melleton, Jérémie. "Modalités du recyclage de la croûte continentale dans l'orogène varisque par traçage in situ des zircons hérités (mesures U -Pb/LA-MC-ICPMS)." Phd thesis, Université d'Orléans, 2008. http://tel.archives-ouvertes.fr/tel-00388706.

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Ce travail de thèse est essentiellement consacré à l'investigation des populations de zircons et de l'âge des protolithes des formations varisques grâce à une datation U-Pb in situ systématique par le couplage Laser/MC-ICPMS, dans des formations orthodérivées, métasédimentaires et magmatiques tardi-orogéniques du Massif Central français et du domaine Sud armoricain. Cette étude a montré que les populations de zircons sont largement héritées, s'étalant de l'Archéen au Paléozoïque inférieur. L'ensemble des pics d'âges obtenus, ainsi que l'absence d'âge mésoprotérozoïque (1.7-1.1 Ga) accréditent l'affinité gondwanienne de ces formations. Des âges maximum de dépôt sont proposés pour les métasédiments des principales unités définies dans le Massif Central. Ces âges maximum de dépôt sont décroissants suivant l'empilement lithotectonique reconnu. En marge de ce travail, nous avons pu déterminer que les âges de mise en place des granitoïdes du Sillon Houiller (Massif Central) et du golfe du Morbihan se situent aux alentours de 300 Ma. Des âges plus anciens, principalement obtenus sur monazite lors d'études antérieures, ont été réinterprétés comme des âges hérités. L'abondance de zircons hérités d'âge ordovicien et néoprotérozoïque met en évidence la large contribution des métagranites et métasédiments fertiles de ces périodes dans la source des granites tardi-orogéniques varisques. Le granite de Sarzeau expose de plus les traces d'un protolithe silurien. Le recyclage de la croûte continentale est caractérisé par une évolution polycyclique au cours de l'orogénèse varisque, avec tout d'abord l'érosion de formations du craton africain, majoritairement d'âge néoprotérozoïque, puis la superposition des événements magmatiques cambro-ordoviciens et syn-orogéniques varisques.

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Cappello, Mariko. "New radiometric age constraints on the Ordovician-Silurian boundary from Anticosti Island (eastern Canada) and the Siljan district (Sweden)." Thesis, 2019. http://hdl.handle.net/1828/11089.

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The transition from the end of the Ordovician to the beginning of the Silurian Period is characterized by the glaciation of the Gondwana paleocontinent, eustatic sea level change, a perturbation to the global carbon cycle and one of the ve major mass extinctions of the Phanerozoic Eon. Due to signi cant sea level fall, the Ordovician-Silurian (O-S) boundary is often marked by hiatus and exposure in the shallow marine geologic record (e.g., Copper et al. [2013]). Two locations that host stratigraphic succession close to the boudary are Anticosti Basin of Quebec (Canada, e.g., Desrochers et al. [2010]), and the carbonate mounds of the Siljan ring district (Dalarna County, Sweden, e.g., Ebbestad et al. [2015]). The exact timing and dynamics of the glaciation and mass extinction are yet to be understood. Similarly, the interplay between those events and the carbon cycle perturbation are still unclear. As a result, there is a serious need for radiometric age constraints in this crucial part of the Paleozoic Era. The acquisition of more radiometric dates, achieved in this study, aims to address the present dearth of absolute dates close to the boundary. The dates produced in this study represent the first modern geochronologic constraints on the O-S boundary, leveraging the development of the EARTHTIME initiative and the latest U-Pb dating techniques that have improved accuracy and allowed for dating of single zircon crystals at <=0.1% precision level. Here I present two new U-Pb zircon ages obtained via bentonite dating. The first bentonite, 443.61+-0.52 Ma (2, including analytical, tracer calibration and decay constant uncertainties) was collected from the base of the Lousy Cove Member, Ellis Bay Formation (Anticosti Island, Quebec, Canada). The second one, 443.28+-0.50 Ma (including analytical, tracer calibration and decay constant uncertainties) comes from a karstic void within the Boda Core Facies of the Boda Formation (Dalarna County, Sweden). U-Pb geochronology (chemical abrasion, isotope dilution, thermal ionization mass spectrometry: CA-ID-TIMS) on single zircons was used to obtain these ages. These results are the closest radiometric ages to the current O-S boundary (compared to any time constraints in the 2012 Geologic Time Scale) and allow to signifcantly reduce the uncertainty of the current age boundary (443.8+-1.5, Cohen et al. [2018]). Furthermore these absolute ages have been used to make models that explore drivers of Earth system change, such as an end-Ordovician global carbon cycle perturbation.
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Ren, Shuang K. "The Ardlethan Tin Field, New South Wales : breccia pipes and mineralization." Phd thesis, 1989. http://hdl.handle.net/1885/12540.

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The Ardlethan Tin Field is located near the western edge of the Lachlan Fold Belt in New South Wales, Australia. The oldest rocks in the Ardlethan Tin Field are metasedimentary rocks of Ordovician age. They were intruded during late Silurian-early Devonian times by the Mine Granite and the Ardlethan Granite dated at 417+2.5 and 410+2.5 Ma respectively. The latter is strongly fractionated and has three daughter phases: the Garnet-Bearing Quartz Feldspar Porphyry (GQFP), the microgranite and the Mine Porphyry. The GQFP represents a marginal phase, the microgranite a moderately fractionated phase and the Mine Porphyry a late stage strongly fractionated phase. Four breccia pipes, the Mine Granite, Carpathia-Blackreef, Stackpool-Godfrey and the White Crystal Breccia Pipes were formed sequentially in three brecciation events. They are hosted by the Mine Granite. Each brecciation event was followed by hydrothermal alteration, and cassiterite and sulphide mineralization. Fluid exsolution during crystallization of the most fractionated sediment and mafic dykes in the breccia pipes indicates a complex evolutionary history during their formation. The materials in the Mine Granite, Carpathia-Blackreef and the Stackpool-Godfrey Breccia Pipes have moved upward significantly. The White Crystal Breccia Pipe is the only one which has collapsed. The mineralization in the breccia pipes was strongly controlled by permeability. The Mine Granite Breccia Pipe has an impermeable central zone of rock flour-supported breccia and a marginal zone of fragment supported breccia. Mineralization of economic grades only occurs in the marginal zone. A similar situation occurs in the upper levels of the Carpathia-Blackreef and Stackpool-Cioclfrey Breccia Pipes. The White Crystal Breccia Pipe contains no rock flour-supported breccia so that mineralization occurs mainly in the central zone. Cassiterite and sulphide mineralization in the breccia pipes is associated with hydrothermal biotite, sericite, tourmaline, quartz, topaz and chlorite. A common paragenetic sequence observed in all the breccia pipes is early cassiterite deposition with sericite, tourmaline and milky quartz, followed by sulphide deposition with clear quartz, toothy quartz, fluorite and cookeite vug infill and chlorite alteration. An independent event of cosalite mineralization, associated with native bismuth and bismuthinite, occurs in fractures and veins postdating the cassiterite and sulphide mineralization in the Blackreef-Godfrey area. The compositions of biotite, tourmaline, muscovite and chlorite in the Ardlethan Granite are enriched in FeO and depleted in MgO compared to biotite, tourmaline, muscovite and chlorite in fresh Mine Granite. Those in the alteration zones formed during rock-fluid reactions are generally of intermediate compositions. Fluid inclusion microthermometric data indicate that cassiterite and milky quartz deposition in the Ardlethan Tin Field occurred at temperatures between 360 and 31 0°C; sulphide and clear quartz between 270 and 220°C; and toothy quartz, fluorite and cookeite between 200 and 150°C. Coexistence of C02-rich and H20-rich fluid inclusions allowed a minimum pressure estimate of about 450 bars during mineralization. Temperatures calculated from the compositions of the hydrothermal biotite, muscovite and chlorite suggest that biotite alteration occurred between 420 and 360oc, sericite alteration between 330 and 290oc and chlorite alteration mainly between 290 and 1 05oC. These results are in good agreement with the fluid inclusion microthermometry and the paragenesis. The oxygen isotope compositions of milky quartz, clear quartz and toothy quartz are mostly between 11.5 and 13.5 per mil regardless of the wide temperature range of their formation. This suggests a complex evolution in the fluid during mineralization probably due to continued rock-fluid equilibria. The sulphur isotope compositions of the sulphides formed during the main stage mineralization are very close to 0 per mil and the carbon isotope values mostly 4.3+ 1.0 per mil. They either support of milky quartz, clear quartz and toothy quartz are mostly between 11.5 and 13.5 per mil regardless of the wide temperature range of their formation. This suggests a complex evolution in the fluid during mineralization probably due to continued rock-fluid equilibria. The sulphur isotope compositions of the sulphides formed during the main stage mineralization are very close to 0 per mil and the carbon isotope values mostly 4.3+ 1.0 per mil. They either support or permit a interpretation that the fluid responsible for the cassiterite and sulphide mineralization was derived from the Ardlethan Granite and continuously equilibrated with the Mine Granite. The sulphur isotope compositions of the sulphides in association with the cosalite mineralization are > 10.0 per mil and indicate that the cosalite mineralization was an independent event. Thermodynamic study of mineral-fluid equilibria suggests that there were continual changes in temperature, pH and redox conditions as the fluid flowed upwards in the breccia pipes. These changes caused various styles of hydrothcnrwl alteration and cassiterite and sulphide depositions. The brecciation and breccia pipe-hosted cassiterite and sulphide mineralization may be interpreted in terms of a dynamic process involving magma fractionation in the Ardlethan Granite, episodic brecciation, fluid flow, rock -fluid reactions, fluid boiling, alteration and mineral deposition. The process started with the fractionation in the Ardlethan Granite. Accumulated volatiles build up an over-pressure which caused brecciation and formation of the Mine Granite Breccia Pipe. At this stage the Ardlethan Granite was only partially crystallized and the brecciation was followed by the intrusion of a differentiated magma, represented by the Mine Porphyry, which moved the materials in the Mine Granite Breccia Pipe upwards. The continual crystallization in the Ardlethan Granite kept a steady supply of fluid which was channelled into the most permeable marginal zones of the breccia pipe. As the fluid flowed upwards, it cooled, reacted with minerals in the brecciated rocks and boiled. The resultant physico-chemical gradients along the fluid paths caused biotite alteration; cassiterite and milky quartz deposition with sericite and tourmaline alteration: sulphide and clear quartz deposition; toothy quartz, fluorite and ite deposition and chlorite alteration sequentially in zones from depth ro surface. Mineral deposition gradually reduced the permeability of the Mine Granite Breccia Pipe and the fluid flux, caused a slow retreat of t vertical zonations. When the Mine Granite was completely sealed by mineral deposition, fluid accumulation started again at depth and resulted in the brecciation of the Carpathia-Blackreef and the Stackpool frey Breccia Pipes. Similar processes occurred. The White Crystal Breccia Pipe represents the third brecciation event in the Ardlethan Tin Field. Its collapse reflects the depletion of volatiles and completion of crystallization of the Ardlethan Granite.

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Books on the topic "Ordovician age"

1

Balding, G. O. Changes in chloride concentration in water from municipal wells that tap aquifers in rocks of Cambrian and Ordovician age in northeastern Illinois, 1915-84. Urbana, Ill: U.S. Dept. of the Interior, U.S. Geological Survey, 1991.

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Balding, G. O. Changes in chloride concentration in water from municipal wells that tap aquifers in rocks of Cambrian and Ordovician age in northeastern Illinois, 1915-84. Urbana, Ill: U.S. Dept. of the Interior, U.S. Geological Survey, 1991.

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P, Candelaria Magell, Reed Christy L, and SEPM (Society for Sedimentary Geology), eds. Paleokarst, karst-related diagenesis, and reservoir development: Examples from Ordovician-Devonian age strata of West Texas and mid-continent : 1992 field trip guidebook, Permian Basin Section-SEPM (Society for Sedimentary Geology). [Midland, Tex.?]: Permian Basin Section, SEPM, 1992.

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Paleokarst, Karst-Related Diagenesis, and Reservoir Development: Examples from Ordovician-Devonian Age Strata of West Texas and the Mid-Continent : 1. Permian Basin Section Sepm, 1992.

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P, Candelaria Magell, Reed Christy L, and SEPM (Society for Sedimentary Geology). Permian Basin Section, eds. Paleokarst, Karst-related diagenesis, and reservoir development: Examples from Ordovician-Devonian age strata of West Texas and the mid-continent : 1992 field trip guidebook, Permian Basin Section-SEPM, Society for Sedimentary Geology. [Texas]: Permian Basin Section-SEPM, 1992.

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P, Candelaria Magell, Reed Christy L, and SEPM (Society for Sedimentary Geology). Permian Basin Section., eds. Paleokarst, Karst-related diagenesis, and reservoir development: Examples from Ordovician-Devonian age strata of West Texas and the mid-continent : 1992 field trip guidebook, Permian Basin Section-SEPM, Society for Sedimentary Geology. [Texas]: Permian Basin Section-SEPM, 1992.

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P, Candelaria Magell, Reed Christy L, and SEPM (Society for Sedimentary Geology). Permian Basin Section., eds. Paleokarst, Karst-related diagenesis, and reservoir development: Examples from Ordovician-Devonian age strata of West Texas and the mid-continent : 1992 field trip guidebook, Permian Basin Section-SEPM, Society for Sedimentary Geology. [Texas]: Permian Basin Section-SEPM, 1992.

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Paleokarst, Karst-related diagenesis, and reservoir development: Examples from Ordovician-Devonian age strata of West Texas and the mid-continent : 1992 field trip guidebook, Permian Basin Section-SEPM, Society for Sedimentary Geology. [Texas]: Permian Basin Section-SEPM, 1992.

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Sheppard, Charles. 2. Ancient reefs and islands. Oxford University Press, 2014. http://dx.doi.org/10.1093/actrade/9780199682775.003.0002.

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‘Ancient reefs and islands’ illustrates that the present day ecology and organization of species on a reef and their behaviour—basically how a reef works—is the result of a very long heritage. Limestone-deposited structures of the Pre-Cambrian, Cambrian, Ordovician, Carboniferous, Permian, Triassic, and Cretaceous periods, the organisms that created them (including ancestors of today’s sponges and corals), and key extinctions are described along with the three different kinds of coral islands seen around the tropical world: coral cays, islands with a solid limestone core, and volcanic or basaltic islands fringed with coral reef. The future of current reef systems, the effects of ocean changes, and the resulting impact on humanity are considered.

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Book chapters on the topic "Ordovician age"

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Perfilova, O. Yu, A. M. Sazonov, M. L. Makhlaev, and A. A. Vorontsov. "Igneous Rocks of the Kachinsk-Shumikhinsky Magmatic Area of Late Ordovician-Early Silurian Age (East Sayan)." In Geological Tour of Devonian and Ordovician Magmatism of Kuznetsk Alatau and Minusinsk Basin, 149–89. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-29559-2_7.

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Douglas, A. G., J. S. Sinninghe Damsté, J. W. de Leeuw, T. I. Eglinton, and M. G. Fowler. "Distribution and Structure of Hydrocarbons and Heterocyclic Sulfur Compounds Released from Four Kerogens of Ordovician Age by Means of Flash Pyrolysis." In Early Organic Evolution, 267–78. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-76884-2_20.

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Fowler, Martin G. "The Influence of Gloeocapsomorpha prisca on the Organic Geochemistry of Oils and Organic-Rich Rocks of Late Ordovician Age from Canada." In Early Organic Evolution, 336–56. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-76884-2_26.

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Key, Erica, and Patricia H. Cashman. "Insights from the Golconda Summit Area, Nevada: Late Paleozoic Structures, Regional Strike-Slip Offset, and Correlation of the “Comus Formation”." In Late Paleozoic and Early Mesozoic Tectonostratigraphy and Biostratigraphy of Western Pangea, 89–101. SEPM (Society for Sedimentary Geology), 2022. http://dx.doi.org/10.2110/sepmsp.113.08.

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Detailed mapping and reevaluation of biostratigraphic data provide new insights into the regional stratigraphic significance of the Ordovician Comus Formation at its type locality at Iron Point, Edna Mountain, Humboldt County, Nevada. Mapping of the internal stratigraphy of the Comus Formation yielded six new subunits and a previously unrecognized formation that is potentially correlative to the Middle Ordovician Eureka Quartzite. The age designation of the Comus Formation was reexamined, using the most current understanding of Ordovician graptolite biostratigraphy. The species of graptolites found in the Comus strata at Iron Point are Late Ordovician, in contrast to the Middle Ordovician age assignment in previous studies. Structural analyses using the new detailed mapping revealed six deformational events at Iron Point. The first fold set, F1, is west-vergent and likely correlative to mid-Pennsylvanian folds observed nearby at Edna Mountain. The second fold set, F2, records north–south contraction and is likely correlative to Early Permian folds observed at Edna Mountain. The King fault is a normal fault that strikes north and dips east. It truncates the F1 and F2 fold sets and has not been active since the Early Permian. The Silver Coin thrust strikes east, places the Ordovician Vinini Formation over the Comus Formation, truncates the King fault, and is not affected by the F1 and F2 fold sets. Timing of the Silver Coin thrust is unknown, but it is likely post-Early Permian based on crosscutting relationships. The West fault strikes southeast and dips southwest. It truncates the Silver Coin thrust on the west, and the fault surface records several phases of motion. Finally, Iron Point is bounded on the east side by the Pumpernickel fault, a normal fault that strikes north and dips east. The movement on this structure is likely related to Miocene to Recent Basin and Range faulting. Several key findings resulted from this detailed study of the Ordovician rocks at Iron Point. (1) Based on detailed mapping of the internal stratigraphy of the Comus Formation at Iron Point, it is here interpreted to be correlative with the autochthonous Late Ordovician Hanson Creek Formation rather than the well-known “Comus Formation” that hosts Carlin-style gold mineralization in the Osgood Mountains to the north. (2) The Comus Formation at Iron Point is autochthonous, and the Roberts Mountains thrust is not present at Iron Point, either at the surface or in the subsurface. (3) The stratigraphic mismatch between Iron Point and Edna Mountain requires a fault with significant lateral offset between the two areas; its current expression could be the West fault. (4) West- and southwest-vergent structures at Iron Point and Edna Mountain are rotated counterclockwise relative to northwest-vergent structures at Carlin Canyon and elsewhere in northern Nevada. This relationship is consistent with large-scale sinistral slip along the continental margin to the west.

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Riggs, Nancy, Brian McConnell, and John Graham. "Sedimentary provenance of Silurian basins in western Ireland during Iapetus closure." In New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2554(16).

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ABSTRACT Three Silurian basin fills, the Llandovery–Wenlock Croagh Patrick and Killary Harbour–Joyce Country successions and the Ludlow–Pridoli Louisburgh–Clare Island succession, overstep the tectonic contacts between elements of the Grampian (Taconic) accretionary history of the Caledonian-Appalachian orogeny in western Ireland. New U-Pb detrital zircon data from lower strata of these Silurian rocks provide insight into basin evolution and paleogeography. The shallow-marine Croagh Patrick succession unconformably overlies the Clew Bay Complex and the northern part of the Ordovician South Mayo Trough. Two samples have zircon populations dominated by Proterozoic grains typical of the Laurentian margin, with few younger grains. Up to 13% of the grains form a cluster at ca. 950–800 Ma, which is younger than known Grenville magmatism on the local Laurentian margin and older than known magmatism from Iapetan rifting; these may be recycled grains from Dalradian strata, derived from distal Tonian intrusions. The Killary Harbour–Joyce Country succession overlies the structural contact between the Lough Nafooey arc and the Connemara Dalradian block and records a transgressive-regressive cycle. Four samples of the Lough Mask Formation show contrasting age spectra. Two samples from east of the Maam Valley fault zone, one each from above Dalradian and Nafooey arc basement, are dominated by Proterozoic grains with ages typical of a Laurentian or Dalradian source, likely in north Mayo. One sample also includes 8% Silurian grains. Two samples from west of the fault overlie Dalradian basement and are dominated by Ordovician grains. Circa 450 Ma ages are younger than any preserved Ordovician rocks in the region and are inferred to represent poorly preserved arc fragments that are exposed in northeastern North America. Cambrian to late Neoproterozoic grains in association with young Ordovician ages suggest derivation from a peri-Gondwanan source in the late stages of Iapetus closure. The Louisburgh–Clare Island succession comprises terrestrial red beds. It unconformably overlies the Clew Bay Complex on Clare Island and is faulted against the Croagh Patrick succession on the mainland. The Strake Banded Formation yielded an age spectrum dominated by Proterozoic Laurentian as well as Ordovician–Silurian ages. Although the basin formed during strike-slip deformation along the Laurentian margin in Ireland and Scotland, sediment provenance is consistent with local Dalradian sources and contemporaneous volcanism. Our results support ideas that Ganderian continental fragments became part of Laurentia prior to the full closure of the Iapetus Ocean.

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Hodgin, Eben B., Francis A. Macdonald, Paul Karabinos, James L. Crowley, and Douglas N. Reusch. "A reevaluation of the tectonic history of the Dashwoods terrane using in situ and isotope-dilution U-Pb geochronology, western Newfoundland." In New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2554(10).

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ABSTRACT Synthesis of the Ordovician Taconic orogeny in the northern Appalachians has been hindered by along-strike variations in Laurentian, Gondwanan, and arc-generated tectonic elements. The Dashwoods terrane in Newfoundland has been interpreted as a peri-Laurentian arc terrane that collided with the Laurentian margin at the onset of the Taconic orogeny, whereas along strike in New England, the More-town terrane marks the leading edge of peri-Gondwanan arcs. The peri-Laurentian affinity of the Dashwoods terrane hinges on the correlation of its oldest metasedimentary rocks with upper Ediacaran to Lower Ordovician rift-drift deposits of the Laurentian Humber margin in western Newfoundland. Here, we report U-Pb dates and trace-element geochemistry on detrital zircons from metasedimentary rocks in the southern Dashwoods terrane that challenge this correlation and provide new insights into the Taconic orogeny. Based on age and trace-element geochemistry of detrital zircons analyzed by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) and chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS), we identified ca. 462–445 Ma sedimentary packages with a mixed provenance consisting of Laurentian, Gondwanan, and arc-derived Cambrian–Ordovician sources. These deposits overlap in age with Upper Ordovician strata of the Badger Group of the Exploits subzone, which also contain Laurentian detritus. We infer dominantly east-directed transport of Laurentian detritus from the Taconic collision zone across a postcollisional arc–back-arc complex at ca. 462–455 Ma followed by dominantly west-directed transport of detritus from the Red Indian Lake arc at ca. 455–445 Ma. Our analysis of zircon inheritance from Dashwoods igneous rocks suggests that 1500–900 Ma Laurentian crystalline basement of the Humber margin is an unlikely source of Dashwoods inherited zircon. Instead, a more cosmopolitan Laurentian inheritance may be best explained as sourced from subducted Laurentian sediment. Our results demonstrate that the sampled metasedimentary units from the southern Dashwoods terrane do not correlate with rift-drift strata of the Humber margin as previously proposed, nor with the basement of the Moretown terrane; yet, these Middle to Upper Ordovician successions suggest the potential for an alternative plate-tectonic model in which the Taconic orogeny may have been initiated by collision of Gondwanan arc terranes that closed the main tract of the Iapetus Ocean along the Baie Verte–Brompton Line.

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Baird, Graham B., Fawna J. Korhonen, and Kevin R. Chamberlain. "Pressure-temperature-deformation-time path for the Seve Nappe Complex, Kebnekaise Massif, Arctic Swedish Caledonides." In New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2554(12).

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ABSTRACT The Seve Nappe Complex in the Scandinavian Caledonides records a range of peak metamorphic conditions and timings. To better understand pressure-temperature-deformation-time differences throughout the complex and possible tectonic scenarios, metamorphosed mafic rocks within the Tarfala Valley of the Kebnekaise Massif (Sweden) were investigated using integrated petrologic and geochronologic techniques. Thermodynamic modeling of two samples using domainal and whole-rock compositions integrated with mineral chemistry, mineral textures, and titanite and zircon U-Pb geochronology constrained a portion of the pressure-temperature (P-T) path. Peak metamorphic conditions of 590–660 °C and 9.7–10.5 kbar were followed by near-isothermal decompression or a subsolidus clockwise P-T path. Amphibolite units in the valley record retrograde conditions at 450–550 °C at less than 7.5 kbar, although mineral modes and textures are most consistent with pressures <4 kbar. The majority of titanite growth occurred due to the introduction of hydrous fluids during cooling and following exhumation to midcrustal levels. U-Pb ages of retrograde titanite define a spread from ca. 480 to 449 Ma, and the oldest age is interpreted to constrain the timing of retrogression following exhumation. This interpretation is supported by a U-Pb zircon crystallization age of 481 ± 7 Ma for a metamorphosed intermediate to felsic synkinematic dike hosted in one of the amphibolite units. These results indicate that the Kebnekaise region records Early Ordovician deformation and metamorphism that was of lower grade compared to other Seve Nappe Complex locations to the south. The tectonic history of these rocks includes metamorphism and exhumation during the Cambrian–Ordovician pre-Scandian event, followed by thrusting of the Seve Nappe Complex and neighboring rocks onto Baltica during the Silurian Scandian orogeny.

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Martens, Uwe C., and Roberto S. Molina Garza. "Mexico: Basement framework and pre-Cretaceous stratigraphy." In Southern and Central Mexico: Basement Framework, Tectonic Evolution, and Provenance of Mesozoic–Cenozoic Basins, 1–27. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2546(01).

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ABSTRACT Provenance determinations of sediment deposited in circum–Gulf of Mexico basins rely on understanding the geologic elements present in the basement provinces located from northeast Mexico to Honduras. Relevant geologic features of these provinces are herein summarized in text and pictorial form, and they include the Huizachal-Peregrina uplift, western Gulf of Mexico, Huayacocotla, Zapoteco, Mixteca, Xolapa, Juchatengo, Cuicateco, Mixtequita, south-central Chiapas, southeast Chiapas, western Guatemala, central Guatemala, Maya Mountains, and the Chortis block. We recognized basement elements of local character that serve as fingerprints for specific source areas. However, many elements are ubiquitous, such as 1.4–0.9 Ga, high-grade metamorphic rocks that occur both as broad exposures and as inliers in otherwise reworked crust. Xenocrystic and detrital zircon of Mesoproterozoic age is very common and hence not diagnostic of provenance. Neoproterozoic rocks are very scarce in Mexican basement provinces. However, Ediacaran–Cambrian detrital zircon grains are found in Mexican Paleozoic strata; these were possibly derived from distant sources in Gondwana and Pangea. Ordovician–Silurian magmatism is present in approximately half the provinces; magmatic detrital zircon of such age is somewhat informative in terms of provenance. More useful populations are detrital zircon grains with Ordovician–Silurian metamorphic overgrowth, which seem to be mainly sourced from the Mixteca region or the southern Chiapas Massif. Devonian basement has only been discovered in the Maya Mountains of Belize, and detrital zircon of such age seems to be characteristic of that source. A similar case can be made about Carboniferous zircon and the Acatlán Complex, Middle Pennsylvanian zircon and Juchatengo plutons, and Late Triassic zircon and the basement exposed in central Guatemala. In all these cases, the age and geographic extent of the zircon source are restricted and serve as a distinct fingerprint. Plutons of Permian–Early Triassic age are widespread, and detrital zircon grains from them are rather nonspecific indicators of source area. Future dating of detrital white mica using 40Ar-39Ar could help in recognizing Carboniferous–Triassic schist from more restricted schist occurrences such as west Cuicateco (Early Cretaceous) and central Guatemala (Late Cretaceous).

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Schmitz, Birger, Martin Schmieder, Shiyong Liao, Ellinor Martin, and Fredrik Terfelt. "Impact-crater ages and micrometeorite paleofluxes compared: Evidence for the importance of ordinary chondrites in the flux of meteorites and asteroids to Earth over the past 500 million years." In From the Guajira Desert to the Apennines, and from Mediterranean Microplates to the Mexican Killer Asteroid: Honoring the Career of Walter Alvarez. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.2557(18).

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ABSTRACT Although the ~200 impact craters known on Earth represent only a small fraction of the craters originally formed, the available data suggest an excess of craters by one order of magnitude, in number, in the interval ca. 470–440 Ma during the Ordovician. Most of these “excess” craters may be related to the breakup of the L-chondrite parent body (LCPB) in the asteroid belt at 465.8 ± 0.3 Ma. This is the only obvious peak in the crater-age record that can currently be attributed to an asteroid breakup and shower event. Spatial crater densities in regions with high potential for crater preservation (e.g., Canada and Scandinavia) support a one order-of-magnitude increase in the flux of large (>0.1 km) impactors following the LCPB breakup. A similar pattern as seen in the cratering record is emerging in studies of the flux of micrometeoritic chrome spinel through the Phanerozoic, with so far only one major spike in the flux, and associated with the LCPB breakup. Similarly, the record of K-Ar and (U-Th)/He gas retention ages of recently fallen meteorites only locates one major breakup, the LCPB event, during the Phanerozoic. On the other hand, astronomical backtracking studies of the orbits of asteroid family members indicate ~70 major family-forming breakups within the past ~540 m.y., which apparently have not left any clear imprint in Earth’s geological record. The chrome-spinel grains recovered in our studies dominantly represent large micrometeorites (>300 µm) and as such are also representative of the flux of larger meteorites to Earth. An observed, nearly constant flux of ordinary chondritic chrome-spinel grains throughout the Phanerozoic, except after the LCPB event, indicates that the present situation—with a clear dominance of ordinary chondritic matter in the large (>500 µm) micrometeorite and macroscopic meteorite fractions—has prevailed at least for the last 500 m.y. This is also supported by generally high ratios in our samples of chrome-spinel grains from ordinary chondrites compared to other types of spinel-bearing meteorites. The chrome-spinel data together with the abundance of fossil meteorites (1–21 cm in diameter) on the Ordovician seafloor also sets an upper limit at one order of magnitude on the increase in flux of large (>0.1-km-diameter) L-chondritic projectiles to Earth following the LCPB. Such an increase would not stand out in the global cratering record if ordinary chondritic impactors had only represented a small fraction of all Phanerozoic impactors. We argue that the origin of impactors delivered to Earth during the past 500 m.y. has mirrored the flux of large micrometeorites and meteorites, with ordinary chondrites being an important or, most likely, the dominant (in numbers) component throughout.

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Bradley, Mark A., L. Page Anderson, Nathan Eck, and Kevin D. Creel. "Chapter 16: Giant Carlin-Type Gold Deposits of the Cortez District, Lander and Eureka Counties, Nevada." In Geology of the World’s Major Gold Deposits and Provinces, 335–53. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.16.

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Abstract The Cortez district is in one of the four major Carlin-type gold deposit trends in the Great Basin province of Nevada and contains three giant (>10 Moz) gold orebodies: Pipeline, Cortez Hills, and Goldrush, including the recently discovered Fourmile extension of the Goldrush deposit. The district has produced >21 Moz (653 t) of gold and contains an additional 26 Moz (809 t) in reserves and resources. The Carlin-type deposits occur in two large structural windows (Gold Acres and Cortez) of Ordovician through Devonian shelf- and slope-facies carbonate rocks exposed through deformed, time-equivalent lower Paleozoic siliciclastic rocks of the overlying Roberts Mountains thrust plate. Juxtaposition of these contrasting Paleozoic strata occurred during the late Paleozoic Antler orogeny along the Roberts Mountains thrust. Both upper and lower plate sequences were further deformed by Mesozoic compressional events. Regional extension, commencing in the Eocene, opened high- and low-angle structural conduits for mineralizing solutions and resulted in gold deposition in reactive carbonate units in structural traps, including antiforms and fault-propagated folds. The Pipeline and Cortez Hills deposits are located adjacent to the Cretaceous Gold Acres and Jurassic Mill Canyon granodioritic stocks, respectively; although these stocks are genetically unrelated to the later Carlin-type mineralization event, their thermal metamorphic aureoles may have influenced ground preparation for later gold deposition. Widespread decarbonatization, argillization, and silicification of the carbonate host rocks accompanied gold mineralization, with gold precipitated within As-rich rims on fine-grained pyrite. Pipeline and Cortez Hills also display deep supergene oxidation of the hypogene sulfide mineralization. Carlin-type mineralization in the district is believed to have been initiated in the late Eocene (>35 Ma) based on the age of late- to postmineral rhyolite dikes at Cortez Hills. The Carlin-type gold deposits in the district share common structural, stratigraphic, alteration, and ore mineralogic characteristics that reflect common modes of orebody formation. Ore-forming fluids were channeled along both low-angle structures (Pipeline, Goldrush/Fourmile) and high-angle features (Cortez Hills), and gold mineralization was deposited in Late Ordovician through Devonian limestone, limy mudstone, and calcareous siltstone. The Carlin-type gold fluids are interpreted to be low-salinity (2–3 wt % NaCl equiv), low-temperature (220°–270°C), and weakly acidic, analogous to those in other Carlin-type gold deposits in the Great Basin. The observed characteristics of the Cortez Carlin-type gold deposits are consistent with the recently proposed deep magmatic genetic model. Although the deposits occur over a wide geographic area in the district, it is possible that they initially formed in greater proximity to each other and were then spatially separated during Miocene and post-Miocene regional extension.

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Conference papers on the topic "Ordovician age"

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Sheffield, Sarah L., William Ausich, and Colin D. Sumrall. "NEW ORDOVICIAN-AGE HOLOCYSTITES FROM ANTICOSTI ISLAND, QUEBEC." In GSA Annual Meeting in Denver, Colorado, USA - 2016. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016am-280869.

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Cappello, Marikò, Jon Husson, Blair Schoene, Kristin Bergmann, Seth Finnegan, and David S. Jones. "RADIOMETRIC AGE CONSTRAINTS ON THE ORDOVICIAN-SILURIAN BOUNDARY FROM EASTERN CANADA AND SWEDEN." In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-321432.

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Zinke, Sally G., and Steven A. Tedesco. "Integrated approach in exploring for Dolomite breccias of Middle Ordovician Age, Eastern U.S." In SEG Technical Program Expanded Abstracts 1996. Society of Exploration Geophysicists, 1996. http://dx.doi.org/10.1190/1.1826330.

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Kopylov, I. S. "BITUMINOLOGICAL INDICATORS PROSPECTS OF OIL AND GAS POTENTIAL IN THE WESTERN OF THE SIBERIAN PLATFORM." In Проблемы минералогии, петрографии и металлогении. Научные чтения памяти П. Н. Чирвинского. ПЕРМСКИЙ ГОСУДАРСТВЕННЫЙ НАЦИОНАЛЬНЫЙ ИССЛЕДОВАТЕЛЬСКИЙ УНИВЕРСИТЕТ, 2022. http://dx.doi.org/10.17072/chirvinsky.2022.133.

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Comprehensive geochemical studies were carried out in the west of the Si-berian platform in the basin of the river. Podkamennaya Tunguska. According to the bituminological indicators in the terrigenous-carbonate rocks of the Middle-Upper Cambrian and Ordovician age of the hypergenesis zone, 62 anomalies were estab-lished. In structural and tectonic terms, 38 bituminological anomalies are confined to local positive structures, which can be considered promising for oil and gas explora-tion

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Stackelberg, Paul E., Zoltan Szabo, and Bryant C. Jurgens. "RADIUM MOBILITY AND THE AGE OF GROUNDWATER IN DRINKING-WATER SUPPLIES FROM THE CAMBRIAN-ORDOVICIAN AQUIFER SYSTEM." In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-294558.

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Avila, Teresa D., Matthew R. Saltzman, Elizabeth M. Griffith, and John Olesik. "REFINING THE AGE OF THE MIDDLE-LATE ORDOVICIAN INFLECTION POINT IN SEAWATER 87SR/86SR USING CONODONT APATITE." In GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-333067.

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Paktovsky, Yuri Germanovich. "The problem of diamond content of the Pomyanennovskaya suite (South Cis-Tyman, Perm Region)." In Проблемы минералогии, петрографии и металлогении. Научные чтения памяти П. Н. Чирвинского. ПЕРМСКИЙ ГОСУДАРСТВЕННЫЙ НАЦИОНАЛЬНЫЙ ИССЛЕДОВАТЕЛЬСКИЙ УНИВЕРСИТЕТ, 2022. http://dx.doi.org/10.17072/chirvinsky.2022.199.

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The polymictic composition of the rocks of the Pomyanennovskaya suite indicates their difference from the quartz rocks of the Upper Ordovician in the South Cis-Tyman, which is the basis of the method of relative «lithochronology» for the «mute» sections of the Early Paleozoic in the region. According to the lithological criterion, the rocks of the Pomyanennovskaya suite can be correctly distinguished from the composition of the Polyudovskaya suite (O3pl) into a local stratigraphic taxon, possibly comparable in age to the Alkesvozhskaya sequence (Є3–O1) of the Northern Urals. The diamond content of the Pomyanennovskaya suite indicates the possibility of the existence of intermediate Precambrian reservoirs in the Urals.

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Stackelberg, Paul E., Zoltan Szabo, and Bryant C. Jurgens. "RADIUM MOBILITY AND THE AGE OF GROUNDWATER IN PUBLIC-DRINKING-WATER SUPPLIES FROM THE CAMBRIAN-ORDOVICIAN AQUIFER SYSTEM." In 52nd Annual North-Central GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018nc-311452.

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Bunyon, Enock Q., and Adam Schoonmaker. "GEOCHEMICAL STUDY OF LIKELY CAMBRIAN OR ORDOVICIAN AGE ROCKS OF THE AVERY BROOK FORMATION AND AN UNNAMED TONALITE NEAR CAUCOMGOMOC LAKE, NORTHERN MAINE." In 54th Annual GSA Northeastern Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019ne-328512.

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Zhang, Shunxin. "CONODONTS AS A TOOL IN ESTABLISHING THE AGE AND STRATIGRAPHIC POSITION OF UPPER ORDOVICIAN PETROLEUM SOURCE ROCK INTERVALS ACROSS HUDSON BAY PLATFORM, CANADA." In GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-330999.

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Reports on the topic "Ordovician age"

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Fallas, K. M., and W. Matthews. Age dating of a bentonite in the Duo Lake Formation, western Mackenzie Mountains, Northwest Territories. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/328830.

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In the Misty Creek Embayment of the western Mackenzie Mountains, Duo Lake Formation locally includes minor volcanic deposits associated with Marmot Formation volcanism. A bentonite layer from an outcrop of graptolitic shale found in NTS map area 106-B, in the upper part of the Duo Lake Formation, was sampled for U-Pb zircon dating. Analytical results yielded a dominant population of grains with a concordia age of 439.8 ± 3.0 Ma, interpreted as the age of deposition. Minor inherited zircon populations yielded ages ranging from approximately 1200 to 2850 Ma. Observed graptolites from the same outcrop likely range from Middle Ordovician to Early Silurian and are compatible with the interpreted U-Pb age of the bentonite. Previously known Middle and Late Ordovician volcanic activity in the Misty Creek Embayment is here expanded to include Early Silurian activity, and serves as a proxy for the timing of active extensional tectonism in the basin.

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Cecile, M. P., B. S. Norford, G. S. Nowlan, and T. T. Uyeno. Lower Paleozoic stratigraphy and geology, Richardson Mountains, Yukon (with stratigraphic and paleontological appendices). Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329454.

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The Richardson Trough was a rift basin on the southern margin of an ancestral Iapetus Ocean. It was part of a complex paleogeography that included at least two major rift basins on western Franklinian and northern Cordilleran continental shelves. This paleogeography included the Ogilvie Arch, Porcupine Platform, Blackstone 'supra-basin', Babbage Basin, Husky Lakes Arch, Richardson Trough, Mackenzie Arch, Lac des Bois Platform, and the White Mountains and Campbell uplifts. The Richardson Trough was the failed arm of a triple rift system that formed when an early Paleozoic Iapetus Ocean developed north of the trough. The Richardson Trough displays a classic 'steer's head' profile with two rift fill cycles. The first features late early to middle late Cambrian rifting and late late Cambrian to late Early Ordovician post-rift subsidence; the second, late Early Ordovician to early Silurian rifting and late early Silurian to early Middle Devonian post-rift subsidence. Lower Paleozoic strata exposed in the Richardson Trough range in age from middle Cambrian to early Middle Devonian and are similar to strata in their sister rift, the Misty Creek Embayment. Before this study, the stratigraphic units defined for the Richardson Trough were the Slats Creek Formation and the Road River Formation. Here, the Slats Creek Formation and a new Road River Group are recognized. In order, this group consists of the middle and/or late Cambrian to Early Ordovician Cronin Formation; the early Early Ordovician to latest early Silurian Mount Hare Formation; the early Silurian to late Silurian Tetlit Formation; and the late Silurian to early Middle Devonian Vittrekwa Formation. These Road River Group strata are unconformably overlain by the late Middle to Late Devonian Canol Formation (outcrop) and by the Early Devonian Tatsieta Formation (subsurface).

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Bingham-Koslowski, N., S. Zhang, and T. McCartney. Lower Paleozoic strata in the Labrador-Baffin Seaway (Canadian margin) and Baffin Island. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/321827.

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Lower Paleozoic strata occur offshore Labrador (Middle to Upper Ordovician), offshore Baffin Island in western Davis Strait (Upper Ordovician), as well as onshore Baffin Island (Cambrian to Silurian). Paleozoic carbonate rocks (limestone and dolostone units) dominate with occurrences of siliciclastic strata found in the offshore Labrador subsurface (in the Freydis B-87 well) and in outcrop on Baffin Island. In the Labrador-Baffin Seaway, Lower Paleozoic strata primarily exist as isolated erosional remnants, where historically, minimal effort has been made to correlate Paleozoic outliers due to their lateral discontinuity coupled with inconsistent age data. The Lower Paleozoic of the Labrador-Baffin Seaway and Baffin Island can be viewed as two subsets that do not appear to be correlatable: the southern Lower Paleozoic of the Labrador margin and the northern Lower Paleozoic of the southeastern Baffin Shelf and onshore Baffin Island.

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VandenBerg, R. D., P. B. Kabanov, K E Dewing, and E. A. Atkinson. Geological and geochemical data from the Canadian Arctic Islands, part XVIII: XRF and TOC data, and formation tops in exploration wells from the Devonian clastic wedge and underlying strata, Northwest Territories and Nunavut. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329642.

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This collection of data comprises new XRF data, TOC data, and a new table of formation tops for the lower portion of the Devonian clastic wedge (Weatherall, Cape de Bray and Blackley formations sensu Embry and Klovan, 1976) and the underlying basinal and carbonate-platform strata of variable Ordovician to Lower-Middle Devonian age. Main results include ED-XRF data for 15 well sections within the N.W.T. jurisdiction of the SW Arctic Archipelago. These XRF data were obtained in 2018- 2020 through non-destructive measurements of drillhole cutting samples using a Bruker Tracer IV instrument. Testing of these samples has been restricted to preserve them for future study as they are irreplaceable. The goal of using the non destructives XFR has given us a methodology that does not harm these samples. We find this to be a reasonable method when data is required but no destructive testing is permitted, such as in these legacy wells. Reading acquisition procedure and instrument calibrations are discussed herein. These XRF logs cover cumulatively 12,538 m of well sections, which is the best attainable physical coverage for these strata in the absence of representative cores. For each section surveyed with XRF, we provide graphical striplogs with geophysical logs, descriptive lithology, XRF elemental logs, biostratigraphic data, and, selectively, synthetic seismograms and TOC data. Scientific discussion based on these results is a subject of a separate paper-in-preparation, (Kabanov, P. 2020.)

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Gill, S. B., S. J. Piercey, and C. A. Devine. Preliminary mineralogy of barite-associated sulphide mineralization in the Ordovician Zn-Pb-Cu-Ag-Au Lemarchant volcanogenic massive sulphide deposit, Newfoundland and Labrador. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2013. http://dx.doi.org/10.4095/292708.

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Mueller, C., S. J. Piercey, M. G. Babechuk, and D. Copeland. Stratigraphy and lithogeochemistry of the Goldenville horizon and associated rocks, Baie Verte Peninsula, Newfoundland. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328990.

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The Goldenville horizon in the Baie Verte Peninsula is an important stratigraphic horizon that hosts primary (Cambrian to Ordovician) exhalative magnetite and pyrite and was a chemical trap for younger (Silurian to Devonian) orogenic gold mineralization. The horizon is overlain by basaltic flows and volcaniclastic rocks, is intercalated with variably coloured argillites and cherts, and underlain by mafic volcaniclastic rocks; the entire stratigraphy is cut by younger fine-grained mafic dykes and coarser gabbro. Lithogeochemical signatures of the Goldenville horizon allow it to be divided into high-Fe iron formation (HIF; &gt;50% Fe2O3), low-Fe iron formation (LIF; 15-50% Fe2O3), and argillite with iron minerals (AIF; &lt;15% Fe2O3). These variably Fe-rich rocks have Fe-Ti-Mn-Al systematics consistent with element derivation from varying mineral contributions from hydrothermal venting and ambient detrital sedimentation. Post-Archean Australian Shale (PAAS)-normalized rare earth element (REE) signatures for the HIF samples have negative Ce anomalies and patterns similar to modern hydrothermal sediment deposited under oxygenated ocean conditions. The PAAS-normalized REE signatures of LIF samples have positive Ce anomalies, similar to hydrothermal sediment deposited under anoxic to sub-oxic conditions. The paradoxical Ce behaviour is potentially explained by the Mn geochemistry of the LIF samples. The LIF have elevated MnO contents (2.0-7.5 weight %), suggesting that Mn from hydrothermal fluids was oxidized in an oxygenated water column during hydrothermal venting, Mn-oxides then scavenged Ce from seawater, and these Mn-oxides were subsequently deposited in the hydrothermal sediment. The Mn-rich LIF samples with positive Ce anomalies are intercalated with HIF with negative Ce anomalies, both regionally and on a metre scale within drill holes. Thus, the LIF positive Ce anomaly signature may record extended and particle-specific scavenging rather than sub-oxic/redox-stratified marine conditions. Collectively, results suggest that the Cambro-Ordovician Taconic seaway along the Laurentian margin may have been completely or near-completely oxygenated at the time of Goldenville horizon deposition.

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Fallas, K. M., and R. B. MacNaughton. Bedrock mapping and stratigraphic studies in the Mackenzie Mountains, Franklin Mountains, Colville Hills, and adjacent areas of the Northwest Territories, Geo-mapping for Energy and Minerals program 2009-2019. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/326093.

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The Geo-mapping for Energy and Minerals (GEM) program provided an opportunity to update bedrock geological maps for nearly 92 000 km2 of the northwestern portion of the mainland area of the Northwest Territories. Twenty-four new maps (at the scale of 1:100 000 or 1:250 000) cover a region from the Colville Hills southwestward into the Mackenzie Mountains, including areas of significant mineral and energy resource potential. New mapping was informed by archived Geological Survey of Canada data, notably from Operation Norman (1968-1970), as well as by public-domain industry data. Maps incorporate numerous stratigraphic revisions that postdate Operation Norman, including GEM program innovations affecting Neoproterozoic (specifically Tonian and Ediacaran), Cambrian, and Ordovician units. In this paper, the mapping effort and stratigraphic revisions are documented, a preliminary treatment of structural geology is provided, and related subsurface studies are summarized. Following GEM, GIS-enabled bedrock maps will be available for a swath of territory stretching from the edge of the Selwyn Basin, near the Yukon border, to the Brock Inlier in the northeastern portion of the mainland area of the Northwest Territories.

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Chidsey, Thomas C., David E. Eby, Michael D. Vanden Berg, and Douglas A. Sprinkel. Microbial Carbonate Reservoirs and Analogs from Utah. Utah Geological Survey, July 2021. http://dx.doi.org/10.34191/ss-168.

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Multiple oil discoveries reveal the global scale and economic importance of a distinctive reservoir type composed of possible microbial lacustrine carbonates like the Lower Cretaceous pre-salt reservoirs in deepwater offshore Brazil and Angola. Marine microbialite reservoirs are also important in the Neoproterozoic to lowest Cambrian starta of the South Oman Salt Basin as well as large Paleozoic deposits including those in the Caspian Basin of Kazakhstan (e.g., Tengiz field), and the Cedar Creek Anticline fields and Ordovician Red River “B” horizontal play of the Williston Basin in Montana and North Dakota, respectively. Evaluation of the various microbial fabrics and facies, associated petrophysical properties, diagenesis, and bounding surfaces are critical to understanding these reservoirs. Utah contains unique analogs of microbial hydrocarbon reservoirs in the modern Great Salt Lake and the lacustrine Tertiary (Eocene) Green River Formation (cores and outcrop) within the Uinta Basin of northeastern Utah. Comparable characteristics of both lake environments include shallowwater ramp margins that are susceptible to rapid widespread shoreline changes, as well as compatible water chemistry and temperature ranges that were ideal for microbial growth and formation/deposition of associated carbonate grains. Thus, microbialites in Great Salt Lake and from the Green River Formation exhibit similarities in terms of the variety of microbial textures and fabrics. In addition, Utah has numerous examples of marine microbial carbonates and associated facies that are present in subsurface analog oil field cores.

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Jackson, G. D. Bedrock geology, northwest part of Nuluujaak Mountain, Baffin Island, Nunavut, part of NTS 37-G/5. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/314670.

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The map area lies about 40 km northwest of Baffinland's iron mine. Dykes of unit mAnA3 within unit mAnA2 suggest that unit mAnA2 predates unit mAnA3. Unit nAMqf, basal Mary River Group unit, includes regolith material from units mAnA2 and mAnA3. Unit mAnAm may include some dykes of unit nAMb. The Mary River Group was deposited in a volcanic-arc environment, yielding zircon U-Pb ages mostly in the range of 2.88 to 2.72 Ga. Iron-formation (unit nAMi) is approximately 276 m thick locally, with oxide facies (unit nAMio) being most abundant. The quartzite triangle west of 'Iron lake' (unofficial name) may be a small horst. The main east-west-trending synclinal fold, including the area around 'Iron lake' and the no. 4 ore deposit, is upright, nearly isoclinal, and plunges mostly easterly at both ends with small scale anticlines and synclines in the middle. Magnetite constitutes about 75% of high-grade iron deposits in the north limb, whereas hematite predominates in south-limb deposits. K-Ar and Rb-Sr ages indicate middle Paleoproterozoic overprinting. Central Borden Fault Zone was active at ca. 1.27 Ga and during or after Ordovician time. Note: please be aware that the information contained in CGM 408 is based on legacy data from the 1960-1990s and that it has been superseded by regional-scale information contained in CGM 403.

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Mueller, C., S. J. Piercey, M. G. Babechuk, and D. Copeland. Stratigraphy and lithogeochemistry of rocks from the Nugget Pond Deposit area, Baie Verte Peninsula, Newfoundland. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328989.

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Stratigraphic and lithogeochemical data were collected from selected drill core from the Nugget Pond gold deposit in the Betts Cove area, Newfoundland. The stratigraphy consists of a lower unit of basaltic rocks that are massive to pillowed (Mount Misery Formation). This is overlain by sedimentary rocks of the Scrape Point Formation that consist of lower unit of turbiditic siltstone and hematitic cherts/iron formations (the Nugget Pond member); the unit locally has a volcaniclastic rich-unit at its base and grades upwards into finer grained volcaniclastic/turbiditic rocks. This is capped by basaltic rocks of the Scrape Point Formation that contain pillowed and massive mafic flows that are distinctively plagioclase porphyritic to glomeroporphyritic. The mafic rocks of the Mount Misery Formation have island arc tholeiitic affinities, whereas Scrape Point Formation mafic rocks have normal mid-ocean ridge (N-MORB) to backarc basin basalt (BABB) affinities. One sample of the latter formation has a calc-alkalic affinity. All of these geochemical features are consistent with results and conclusions from previous workers in the area. Clastic sedimentary rocks and Fe-rich sedimentary rocks of the Scrape Point Formation have features consistent with derivation from local, juvenile sources (i.e., intra-basinal mafic rocks). The Scrape Point Formation sedimentary rocks with the highest Fe/Al ratios, inferred to have greatest amount of hydrothermally derived Fe, have positive Ce anomalies on Post-Archean Australian Shale (PAAS)-normalized trace element plots. These features are consistent with having formed via hydrothermal venting into an anoxic/ sub-oxic water column. Further work is needed to test whether these redox features are a localized feature (i.e., restricted basin) or a widespread feature of the late Cambrian-early Ordovician Iapetus Ocean, as well as to delineate the role that these Fe-rich sedimentary rocks have played in the localization of gold mineralization within the Nugget Pond deposit.

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