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Arenig

February 16, 2024

For the mountains in Wales, see Arenigs.

In geology, the Arenig (or Arenigian) is a time interval during the Ordovician period and also the suite of rocks which were deposited during this interval.

Arenig Fawr, the mountain which lends its name to the geological series

History edit

The term was first used by Adam Sedgwick in 1847 with reference to the "Arenig Ashes and Porphyries" in the neighbourhood of Arenig Fawr, in Merioneth, North Wales. The rock-succession in the Arenig district has been recognized by W. G. Fearnsides (“On the Geology of Arenig Fawr and Moel Llanfnant", Q.J.G.S. vol. lxi., 1905, pp. 608–640, with maps). The above succession is divisible into:

  1. A lower series of gritty and calcareous sediments, the "Arenig Series" as it is now understood;
  2. A middle series, mainly volcanic, with shale, the "Llandeilo Series"; and
  3. The shale and limestones of the Bala or Caradoc Stage.

It was to the middle series (2) that Sedgwick first applied the term "Arenig". In the typical region and in North Wales generally the Arenig series appears to be unconformable upon the Cambrian rocks; this is not the case in South Wales.[1]

The Arenig series is represented in North Wales by the Garth Grit and Ty Obry beds, by the Shelve series of the Corndon district, the Skiddaw Slates of the Lake District, the Ballantrae Group of Ayrshire, and by the Ribband Series of slates and shale in Wicklow and Wexford. It may be mentioned here that the "Llanvirn" Series of H. Hicks was equivalent to the bifidus[clarification needed] shale and the Lower Llandeilo Series.[1]

Geochronology edit

In the geologic timescale, the Arenig or Arenigian refers to an age of the Early Ordovician epoch, between 477.7 and 470 million years ago, contemporary with the Floian of the ICS,[2] based on a section in Sweden (Diabasbrottet quarry) and with the same boundaries. The Arenig and Floian rocks are the upper part of the Lower Ordovician and follow the Tremadocian (Gasconadian in North America) which is the lower part. Either is followed by the Middle Ordovician ICS Dapingian or by the Llanvirnian of older chronologies. The Arenig and equivalent Floian are represented in North America by the upper three stages of the Canadian which is followed by the Middle Ordovician Whiterockian which is the lower part of the now shortened Chazyan.

Events edit

The Arenig rocks were deposited during a sudden worldwide rise in sea level resulting in widespread marine transgression. The early Ordovician surge in marine diversity also began around this time.[3]

Brachiopod fauna edit

Incertae sedis brachiopods of the Floian[4]
  • Eurorthisina
  • Tegulella
Acrotretida of the Floian[4]
  • Acanthambonia
  • Cyrbasiotreta
  • Eoconulus
  • Issedonia
  • Karnotreta
  • Lurgiticoma
  • Multispinula
  • Mylloconotreta
  • Numericoma
  • Orthisocrania
  • Polylasma
  • Pomeraniotreta
  • Pseudocrania
  • Scaphelasma
  • Schizotreta
  • Torynelasma
Lingulida of the Floian[4]
  • Acanthorthis
  • Aulonotreta
  • Dictyobolus
  • Ectenoglossa
  • Elliptoglossa
  • Monobolina
  • Paldiskites
  • Paterula
  • Pseudolingula
  • Quasithambonia
  • Rafanoglossa
  • Volborthia
Orthida of the Floian[4]
  • Acanthorthis
  • Acanthotoechia
  • Anchigonites
  • Angusticardinia
  • Anomalorthis
  • Antigonambonites
  • Apomatella
  • Astraborthis
  • Crossiskenidium
  • Dalmanella
  • Desmorthis
  • Diparelasma
  • Eodiorthelasma
  • Eosotrematorthis
  • Estlandia
  • Euorthisina
  • Famatinorthis
  • Fasciculina
  • Ferrax
  • Ffynnonia
  • Fistulogonites
  • Glossorthis
  • Glypterina
  • Hesperonomiella
  • Incorthis
  • Jaanussonites
  • Ladogiella
  • Lomatorthis
  • Monorthis
  • Munhella
  • Nereidella
  • Neumania
  • Nocturneilla
  • Notoscaphidia
  • Oligorthis
  • Orthambonites
  • Orthidiella
  • Orthidium
  • Orthis
  • Oslogonites
  • Panderina
  • Paralenorthis
  • Paurorthina
  • Paurorthis
  • Phragmorthis
  • Platystrophia
  • Platytoechia
  • Polytoechia
  • Pomatotrema
  • Prantlina
  • Productorthis
  • Progonambonites
  • Protohesperonomia
  • Protoskenidiodes
  • Pseudomimella
  • Raunites
  • Rhynchorthis
  • Shoshonorthis
  • Sinorthis
  • Taphrorthis
  • Tarfaya
  • Treioria
  • Trematorthis
  • Valcourea
  • Virgoria
Paternida of the Floian
  • Dictyonites
Pentamerida of the Floian
  • Acanthorthis
  • Acanthoglypha
  • Boreadocamara
  • Camerella
  • Doloresella
  • Hesperotrophia
  • Idiostrophia
  • Imbricatia
  • Karakulina
  • Liricamera
  • Lycophoria
  • Porambonites
  • Rectotrophia
  • Rosella
  • Rugostrophia
  • Stenocamara
  • Syntrophia
  • Syntrophinella
  • Xenelasma

Strophomenida edit

Strophomenida of the Floian
  • Acanthorthis
  • Ahtiella
  • Aporthophyla
  • Borua
  • Calyptolepta
  • Christiania
  • Ingria
  • Leptestia
  • Petroria
  • Plectambonites
  • Reinversella
  • Schedophyla
  • Taffia
  • Tourmakeadia
Trimerellida of the Floian
  • Dinobolus

Cephalopoda edit

Actinocerida
  • Metactinoceras
  • Ordosoceras
  • Polydesmia

Upper edit

The following is a list of Actinocerid genera whose fossils are geochronologically found first in upper Arenig strata. These genera may survive into later portions of the Arenig stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included.

Orthocerida edit

Orthocerids of the Floian[5]
Barrandeocerida of the Floian[5]
Ellesmerocerida of the Floian[5]
Endocerida
  • Campendoceras
  • Dartonoceras
  • Kaipingoceras
  • Kugeloceras
  • Lobosiphon
  • Manitouoceras
  • Mcqueenoceras
  • Mysticoceras
  • Notocycloceras
  • Oderoceras
  • Parapiloceras
  • Phragmosiphon
  • Platysiphon
  • Pliendoceras
  • Retroclitendoceras
  • Stenosiphon
  • Subpenhsioceras
  • Utoceras
  • Yorkoceras
  • Vaginoceras
  • Chisiloceras
  • Cyrtovaginoceras
  • Tallinnoceras
  • Juaboceras
  • Penhsioceras
  • Ventrolobendoceras
Lower

The following is a list of Endocerid genera whose fossils are geochronologically found first in lower Arenig strata. These genera may survive into later portions of the Arenig stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included.

Upper

The following is a list of Endocerid genera whose fossils are geochronologically found first in upper Arenig strata. These genera may survive into later portions of the Arenig stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included.

Intejocerida of the Floian
Oncocerids of the Floian
Nautiloids of the Floian
Tarphycerida
  • Deltoceras
  • Pseudancistroceras
  • Seelyoceras
Lower
Upper

Trilobite fauna edit

Trilobites of the Floian[6]
Agnostida of the Floian'[6]
Asaphida of the Floian[6]
 
Asaphus
Corynexichida of the Floian[6]
Lichida of the Floian[6]
Odontopleurida of the Floian[6]
Phacopida of the Floian
 
Colpocoryphe grandis
Proetida of the Floian
Ptychopariida of the Floian[6]

External links edit

    References edit

    1. ^ a b   One or more of the preceding sentences incorporates text from a publication now in the public domain: Howe, John Allen (1911). "Arenig Group". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 2 (11th ed.). Cambridge University Press. p. 452.
    2. ^ ICS; see Ordovician
    3. ^ . Archived from the original on 2007-11-13. Retrieved 2007-12-11.
    4. ^ a b c d Sepkoski, Jack (2002). . Bulletins of American Paleontology. 364: 560. Archived from the original on 14 October 2004. Retrieved 27 April 2008.
    5. ^ a b c Sepkoski, Jack (2002). . Bulletins of American Paleontology. 364: 560. Archived from the original on 7 May 2008. Retrieved 17 April 2008.
    6. ^ a b c d e f g Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (entry on trilobita)". Bulletins of American Paleontology. 364: 560. Retrieved 19 April 2008.

    February 16, 2024
    arenig, mountains, wales, geology, time, interval, during, ordovician, period, also, suite, rocks, which, were, deposited, during, this, interval, fawr, mountain, which, lends, name, geological, series, contents, history, geochronology, events, brachiopod, fau. For the mountains in Wales see Arenigs In geology the Arenig or Arenigian is a time interval during the Ordovician period and also the suite of rocks which were deposited during this interval Arenig Fawr the mountain which lends its name to the geological series Contents 1 History 2 Geochronology 3 Events 4 Brachiopod fauna 4 1 Strophomenida 5 Cephalopoda 5 1 Upper 5 2 Orthocerida 6 Trilobite fauna 7 External links 8 ReferencesHistory editThe term was first used by Adam Sedgwick in 1847 with reference to the Arenig Ashes and Porphyries in the neighbourhood of Arenig Fawr in Merioneth North Wales The rock succession in the Arenig district has been recognized by W G Fearnsides On the Geology of Arenig Fawr and Moel Llanfnant Q J G S vol lxi 1905 pp 608 640 with maps The above succession is divisible into A lower series of gritty and calcareous sediments the Arenig Series as it is now understood A middle series mainly volcanic with shale the Llandeilo Series and The shale and limestones of the Bala or Caradoc Stage It was to the middle series 2 that Sedgwick first applied the term Arenig In the typical region and in North Wales generally the Arenig series appears to be unconformable upon the Cambrian rocks this is not the case in South Wales 1 The Arenig series is represented in North Wales by the Garth Grit and Ty Obry beds by the Shelve series of the Corndon district the Skiddaw Slates of the Lake District the Ballantrae Group of Ayrshire and by the Ribband Series of slates and shale in Wicklow and Wexford It may be mentioned here that the Llanvirn Series of H Hicks was equivalent to the bifidus clarification needed shale and the Lower Llandeilo Series 1 Geochronology editIn the geologic timescale the Arenig or Arenigian refers to an age of the Early Ordovician epoch between 477 7 and 470 million years ago contemporary with the Floian of the ICS 2 based on a section in Sweden Diabasbrottet quarry and with the same boundaries The Arenig and Floian rocks are the upper part of the Lower Ordovician and follow the Tremadocian Gasconadian in North America which is the lower part Either is followed by the Middle Ordovician ICS Dapingian or by the Llanvirnian of older chronologies The Arenig and equivalent Floian are represented in North America by the upper three stages of the Canadian which is followed by the Middle Ordovician Whiterockian which is the lower part of the now shortened Chazyan Events editThe Arenig rocks were deposited during a sudden worldwide rise in sea level resulting in widespread marine transgression The early Ordovician surge in marine diversity also began around this time 3 Brachiopod fauna editIncertae sedis brachiopods of the Floian 4 Eurorthisina TegulellaAcrotretida of the Floian 4 Acanthambonia Cyrbasiotreta Eoconulus Issedonia Karnotreta Lurgiticoma Multispinula Mylloconotreta Numericoma Orthisocrania Polylasma Pomeraniotreta Pseudocrania Scaphelasma Schizotreta Torynelasma Lingulida of the Floian 4 Acanthorthis Aulonotreta Dictyobolus Ectenoglossa Elliptoglossa Monobolina Paldiskites Paterula Pseudolingula Quasithambonia Rafanoglossa Volborthia Orthida of the Floian 4 Acanthorthis Acanthotoechia Anchigonites Angusticardinia Anomalorthis Antigonambonites Apomatella Astraborthis Crossiskenidium Dalmanella Desmorthis Diparelasma Eodiorthelasma Eosotrematorthis Estlandia Euorthisina Famatinorthis Fasciculina Ferrax Ffynnonia Fistulogonites Glossorthis Glypterina Hesperonomiella Incorthis Jaanussonites Ladogiella Lomatorthis Monorthis Munhella Nereidella Neumania Nocturneilla Notoscaphidia Oligorthis Orthambonites Orthidiella Orthidium Orthis Oslogonites Panderina Paralenorthis Paurorthina Paurorthis Phragmorthis Platystrophia Platytoechia Polytoechia Pomatotrema Prantlina Productorthis Progonambonites Protohesperonomia Protoskenidiodes Pseudomimella Raunites Rhynchorthis Shoshonorthis Sinorthis Taphrorthis Tarfaya Treioria Trematorthis Valcourea Virgoria Paternida of the FloianDictyonitesPentamerida of the FloianAcanthorthis Acanthoglypha Boreadocamara Camerella Doloresella Hesperotrophia Idiostrophia Imbricatia Karakulina Liricamera Lycophoria Porambonites Rectotrophia Rosella Rugostrophia Stenocamara Syntrophia Syntrophinella Xenelasma Strophomenida edit Strophomenida of the FloianAcanthorthis Ahtiella Aporthophyla Borua Calyptolepta Christiania Ingria Leptestia Petroria Plectambonites Reinversella Schedophyla Taffia Tourmakeadia Trimerellida of the FloianDinobolusCephalopoda editActinoceridaMetactinoceras Ordosoceras PolydesmiaUpper edit The following is a list of Actinocerid genera whose fossils are geochronologically found first in upper Arenig strata These genera may survive into later portions of the Arenig stage or even into later geological stages This list should not be thought of in terms of the lifespan of the genera included Leurorthoceras Nybyoceras Actinoceras Wutinoceras Ormoceras Adamsoceras Georgina Orthocerida edit Orthocerids of the Floian 5 EobactritesBarrandeocerida of the Floian 5 PlectocerasEllesmerocerida of the Floian 5 Amsleroceras Apocrinoceras Avoceras Bakeroceras Baltoceras Catoraphinoceras Cochlioceras Copiceras Clelandoceras Cumberloceras Cyclostomiceras Cyrtobaltoceras Desioceras Diaphoroceras Diastoloceras Dwightoceras Dyscritoceras Ectocycloceras Endorioceras Eocyckistomiceras Eothinoceras Hemichoanella Irianoceras Kyminoceras Lawrenceoceras Meikeloceras Microbaltoceras Monogonoceras Ogygoceras Pictetoceras Protocycloceras Quebecoceras Rangeroceras Rhabdiferous Rioceras Rudolfoceras Smithvilloceras Somalinautilus Somalinautilus Somalinautilus Vassaroceras Veneficoceras Ventroloboceras EndoceridaCampendoceras Dartonoceras Kaipingoceras Kugeloceras Lobosiphon Manitouoceras Mcqueenoceras Mysticoceras Notocycloceras Oderoceras Parapiloceras Phragmosiphon Platysiphon Pliendoceras Retroclitendoceras Stenosiphon Subpenhsioceras Utoceras Yorkoceras Vaginoceras Chisiloceras Cyrtovaginoceras Tallinnoceras Juaboceras Penhsioceras Ventrolobendoceras LowerThe following is a list of Endocerid genera whose fossils are geochronologically found first in lower Arenig strata These genera may survive into later portions of the Arenig stage or even into later geological stages This list should not be thought of in terms of the lifespan of the genera included Allopiloceras Choreanoceroides Escharendoceras Lebetoceras Loxochoanella Sewardoceras Telleroceras Clitendoceras Coreanoceras Cotteroceras Piloceras Endoceras Proterovaginoceras Cyrtendoceras Anthoceras Chaohuceras Proterocameroceras Thylacoceras UpperThe following is a list of Endocerid genera whose fossils are geochronologically found first in upper Arenig strata These genera may survive into later portions of the Arenig stage or even into later geological stages This list should not be thought of in terms of the lifespan of the genera included Allocotoceras Cassinoceras Chihlioceras Cyclocyrtendoceras Cyptendoceras Kirkoceras Lobendoceras Najaceras Protocyclendoceras Yehlioceras Nanno Dideroceras Lobocyclendoceras Meniscoceras Paracyclendoceras Cacheoceras Perkinsoceras Williamsoceras Manchuroceras Schmidtoceras Intejocerida of the FloianBajkaloceras Evencoceras Intejoceras RossocerasOncocerids of the FloianPhthanoncoceras ValhallocerasNautiloids of the FloianButtsoceras Centroonoceras Gangshanoceras Geisonoceras Glenisteroceras Michelinoceras Orthoceras Oxfordoceras Rhynchorthoceras Stereoplasmoceras Tajaroceras Wardoceras TarphyceridaDeltoceras Pseudancistroceras SeelyocerasLowerAlaskoceras Moreauoceras Pilotoceras Shumardoceras Pycnoceras Campbelloceras Aphetoceras UpperAethoceras Bentoceras Centrotarphyceras Clytoceras Cycloplectoceras Eichwaldoceras Eurystomites Hardmanoceras Holmiceras Pionoceras Trocholitoceras Wichitoceras Tarphyceras Litoceras Curtoceras Arkoceras Estonioceras TragocerasTrilobite fauna editTrilobites of the Floian 6 Canningella Gogoella Macrogrammus Priceaspis ThymurusAgnostida of the Floian 6 Galbagnostus GeragnostellaAsaphida of the Floian 6 nbsp AsaphusPhthanoncoceras Ampyx Ampyxoides Anebolithus Asaphus Aspidaeglina Australopyge Bergamia Bohemopyge Borogothus Bumastides Ceratolithus Cloacaspis Cnemidopyge Degamella Dionide Dionidella Ellipsotaphrus Falanapis Famatinolithus Globampyx Gog Hanchungolithus Hoekaspis Hungioides Hunnebergia Isocolus Isoteloides Lachnostoma Lannacus Lapidaria Liomegalaspides Megalaspidella Megalaspides Mendolaspis Merlinia Microparia Mioptychopyge Myttonia Ningkianolithus Niobides Ogmasaphus Ogyginus Ogygiocaris Opipeuter Parabasilicus Paraptychopyge Plesiomegalaspis Presbynileus Pricyclopyge Psilacella Psilocara Ptychopyge Rhombampyx Robergiella Seleneceme Stapeleyella Taihungshania Thysanopyge Trigonocercella Tungtzuella Zhenganites Zuninaspis Corynexichida of the Floian 6 Bumastus Dysplanus Ectillaenus Panderia Phillipsinella Pseudocalymene Theamataspis Lichida of the Floian 6 Apatolichas Autoloxolichas Lichakephalina Metopolichas Odontopleurida of the Floian 6 Phthanoncoceras Ceratocephala Diacanthaspis Selenopeltis Phacopida of the Floian nbsp Colpocoryphe grandisBathycheilus Calymenella Ceraurinella Colobinion Colpocoryphe Cybelopsis Cybelurus Diaphanometopus Dindymene Eccoptochile Ectenonotus Encrinurella Encrinuroides Evropeites Gyrometopus Heliomeroides Kanoshia Kawina Kolymella Lehua Lyrapyge Neseuretus Nieszkowskia Ormathops Ovalocephalus Placoparia Platycoryphe Pliomeridius Pliomerops Protoencrinurella Protopliomerella Pseudocybele Pterygometopus Strotactinus Sycophantia Synhomalonotus Toletanaspis Xystocrania Proetida of the FloianAcidiphorus Bathyuriscops Benthamaspis Biolgina Bolbocephalus Carolinites Celmus Ceratopeltis Decoroproetus Dimeropygiella Eleutherocentrus Goniophrys Goniotelina Grinnellaspis Ischyrophyma Ischyrotoma Lutesvillia Oenonella Petigurus Rananasus Raymondaspis Telephina Ptychopariida of the Floian 6 Anaximander Annamitella Balnibarbi Bulnibarbi dubious discuss Bvalbardites Circulocrania Endymionia Etheridgaspis Furcalithus Gymnostomix Lacorsalina Leioshumardia Lordshillia Nambeetella Novakella Oopsites Peraspis Phorocephala Porterfieldia Prosopiscus Pytine Sagavia Selenoharpes Stegnopsis Stenorhachis Svalbardites Tasmanocephalus Turgicephalus YinpanolithusExternal links editpalaeosReferences edit a b nbsp One or more of the preceding sentences incorporates text from a publication now in the public domain Howe John Allen 1911 Arenig Group In Chisholm Hugh ed Encyclopaedia Britannica Vol 2 11th ed Cambridge University Press p 452 ICS see Ordovician Palaeos Paleozoic Ordovician The Arenig Age Archived from the original on 2007 11 13 Retrieved 2007 12 11 a b c d Sepkoski Jack 2002 A compendium of fossil marine animal genera entry on brachiopoda Bulletins of American Paleontology 364 560 Archived from the original on 14 October 2004 Retrieved 27 April 2008 a b c Sepkoski Jack 2002 A compendium of fossil marine animal genera entry on cephalopoda Bulletins of American Paleontology 364 560 Archived from the original on 7 May 2008 Retrieved 17 April 2008 a b c d e f g Sepkoski Jack 2002 A compendium of fossil marine animal genera entry on trilobita Bulletins of American Paleontology 364 560 Retrieved 19 April 2008 Retrieved from https en wikipedia org w index php title Arenig amp oldid 1182434077, wikipedia, wiki, book, books, library,

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