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Becscie Formation

The Becscie Formation is a geologic formation in Quebec. It preserves fossils dating back to the early Silurian period.

Becscie Formation
Stratigraphic range: Early Silurian
TypeGeological formation
Sub-units
  • Fox Point Member (lower)
  • Chabot Member (upper)
UnderliesGun River Formation
OverliesEllis Bay Formation
Thickness80 to 85 meters
Location
Region Quebec
Country Canada

Description

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The Becscie Formation is 80 to 85 meters thick.[1] It overlies the Ordovician-Silurian boundary on Anticosti Island, marking a major oceanic and climatic changeover from the glacial sea-level lowstand and interglacial highstand cycles of the underlying Ellis Bay Formation to the more stable warming climate of the earliest Silurian, and extends approximately parallel to an ancient coastline some 200 km east to west.[1] The formation is divided into two members, a lower Fox Point Member (spanning the Viridita lenticularis Biozone), and an upper Chabot Member (spanning the Virgiana barrandei Biozone).[1]

Fossil content

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Arthropods
Genus Species Presence Material Notes Images
Anticostibolbina Chabot Member.[1] A beyrichiacean ostracod.
Bolbineossia Chabot Member.[1] A beyrichiacean ostracod.
Conbathella Chabot Member.[1] A beyrichiacean ostracod.
Herrmannina H. selwyni Lower Becscie Formation.[1] An ostracod
Zygobursa Chabot Member.[1] A beyrichiacean ostracod.
Brachiopods
Genus Species Presence Material Notes Images
Becscia B. scissura "Occurs commonly in lenses and clusters".[1] An atrypid.[1]
Biparetis Elsewhere known from the early Silurian, but locally rare.[1]
Brachyprion Occurs sparsely in the Chabot Member.[1]
Eospirigerina E. sp. Fox Point Member.[1] An unnamed species, represents earliest known Silurian species of this Ordovician genus.
Hesperorthis Fox Point Member.[1] An orthide.[1]
Isorthis (Ovalella) Fox Point Member.[1] An orthide.[1]
Koigia An athyridid, originally reported as Hindella.[1]
Leptaena Fox Point Member bedding plane.[1]
Mendacella M. udauberis Fox Point Member, rare in the Chabot Member.[1] An orthide.[1]
Saukrodictya Fox Point Member.[1] An orthide.[1]
Virgiana V. barrandei Only in the Chabot Member.[1][2] A large-shelled pentameride.[1]
Viridita V. becsciensis Fox Point Member.[2] "Holotype, YPM 10341, and paratype, YPM 35519".[2]
V. lenticularis Near the top of the Fox Point Member,[1] and the Chabot Member.[2]
Zygospiraella Z. cf. Z. planoconvexa Lower Becscie Formation, rare taxon in the lower Chabot Member.[1]
Bryozoans
Genus Species Presence Material Notes Images
Phaenopora P. superba Fox Point and Chabot Members.[1] "Extends into the overlying Gun River Formation"[3]
Corals
Genus Species Presence Material Notes Images
Acidolites A. arctatus [4] A heliolitid.
A. compactus [4] A heliolitid.
A. lindströmi [4] A heliolitid.
Nanonphyllum N. pelagicum Common in the Chabot Member.[1] A colonial rugose coral.
Paleofavosites More common towards the upper part of the Fox Point Member.[1] A heliolitid tabulate coral.[1]
Palaeophyllum Common in the Chabot Member.[1]
Propora More common towards the upper part of the Fox Point Member.[1] A heliolitid tabulate coral.[1]
Crinoids
Genus Species Presence Material Notes Images
Alopocrinus Fox Point and Chabot members.[1]
Becsciecrinus Fox Point and Chabot members.[1]
Dendrocrinus Chabot Member.[1]
Eumyelodactylus Fox Point Member.[1]
Euspirocrinus Fox Point Member.[1]
Protaxocrinus Fox Point Member.[1]
Xenocrinus Chabot Member.[1]
Gastropods
Genus Species Presence Material Notes Images
Hormotoma Eastern side of Anticosti Island.[1] A hormotomid.
Subulites Eastern side of Anticosti Island.[1] A soleniscid.
Graptolites
Genus Species Presence Material Notes Images
Climacograptus C. typicalis var. atlanticus [5]
Sponges
Genus Species Presence Material Notes Images
Clathrodictyon C. boreale Fox Point and Chabot members.[1] "A single small, spheroidal specimen".[1] A stromatoporoid.[1]
Ecclimadictyon E. macrotuberculatum Chabot Member.[1] A stromatoporoid.
Pachystylostroma Very top of the Chabot Member.[1] A stromatoporoid.

See also

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References

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  1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av Copper, Paul; Jin, Jisuo (2014-04-01). "The revised Lower Silurian (Rhuddanian) Becscie Formation, Anticosti Island, eastern Canada records the tropical marine faunal recovery from the end-Ordovician Mass Extinction". Newsletters on Stratigraphy. 47 (1): 61–83. doi:10.1127/0078-0421/2014/0040. ISSN 0078-0421.
  2. ^ a b c d Jin, Jisuo; Copper, Paul. "Late Ordovician and Early Silurian pentamerid brachiopods of Anticosti Island, Québec, Canada". Palaeontographica Canadiana.
  3. ^ Ross, June Phillips (1960). "Larger Cryptostome Bryozoa of the Ordovician and Silurian, Anticosti Island, Canada: Part I". Journal of Paleontology. 34 (6): 1057–1076. ISSN 0022-3360. JSTOR 1300852.
  4. ^ a b c Dixon, O. A. (January 1986). "The heliolitid coral Acidolites in Ordovician–Silurian rocks of eastern Canada1". Journal of Paleontology. 60 (1): 26–52. doi:10.1017/S002233600002148X. ISSN 0022-3360. S2CID 130759173.
  5. ^ Ruedemann, Rudolf (1947). Graptolites of North America. Geological Society of America. ISBN 978-0-8137-1019-8.


 

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