Becscie Formation Explained
The Becscie Formation is a geologic formation in Quebec. It preserves fossils dating back to the early Silurian period.
Description
The Becscie Formation is 80 to 85 meters thick. 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).
Fossil content
| Arthropods |
|---|
| Genus | Species | Presence | Material | Notes | Images |
|---|
| Anticostibolbina | | Chabot Member. | | A beyrichiacean ostracod. | |
| Bolbineossia | | Chabot Member. | | A beyrichiacean ostracod. | |
| Conbathella | | Chabot Member. | | A beyrichiacean ostracod. | |
| Herrmannina | H. selwyni | Lower Becscie Formation. | | An ostracod | |
| Zygobursa | | Chabot Member. | | A beyrichiacean ostracod. | |
|
| Brachiopods |
|---|
| Genus | Species | Presence | Material | Notes | Images |
|---|
| Becscia | B. scissura | | "Occurs commonly in lenses and clusters". | An atrypid. | |
| Biparetis | | | | Elsewhere known from the early Silurian, but locally rare. | |
| Brachyprion | | Occurs sparsely in the Chabot Member. | | | |
| Eospirigerina | E. sp. | Fox Point Member. | | An unnamed species, represents earliest known Silurian species of this Ordovician genus. | |
| Hesperorthis | | Fox Point Member. | | An orthide. | |
| Isorthis (Ovalella) | | Fox Point Member. | | An orthide. | |
| Koigia | | | | An athyridid, originally reported as Hindella. | |
| Leptaena | | Fox Point Member bedding plane. | | | |
| Mendacella | M. udauberis | Fox Point Member, rare in the Chabot Member. | | An orthide. | |
| Saukrodictya | | Fox Point Member. | | An orthide. | |
| Virgiana | V. barrandei | Only in the Chabot Member.[2] | | A large-shelled pentameride. | |
| Viridita | V. becsciensis | Fox Point Member. | "Holotype, YPM 10341, and paratype, YPM 35519". | | |
| V. lenticularis | Near the top of the Fox Point Member, and the Chabot Member. | | | |
| Zygospiraella | Z. cf. Z. planoconvexa | Lower Becscie Formation, rare taxon in the lower Chabot Member. | | | |
|
| Corals |
|---|
| Genus | Species | Presence | Material | Notes | Images |
|---|
| Acidolites | A. arctatus | [4] | | A heliolitid. | |
| A. compactus | | | A heliolitid. | |
| A. lindströmi | | | A heliolitid. | |
| Nanonphyllum | N. pelagicum | Common in the Chabot Member. | | A colonial rugose coral. | |
| Paleofavosites | | More common towards the upper part of the Fox Point Member. | | A heliolitid tabulate coral. | |
| Palaeophyllum | | Common in the Chabot Member. | | | |
| Propora | | More common towards the upper part of the Fox Point Member. | | A heliolitid tabulate coral. | |
|
| Crinoids |
|---|
| Genus | Species | Presence | Material | Notes | Images |
|---|
| Alopocrinus | | Fox Point and Chabot members. | | | |
| Becsciecrinus | | Fox Point and Chabot members. | | | |
| Dendrocrinus | | Chabot Member. | | | |
| Eumyelodactylus | | Fox Point Member. | | | |
| Euspirocrinus | | Fox Point Member. | | | |
| Protaxocrinus | | Fox Point Member. | | | |
| Xenocrinus | | Chabot Member. | | | |
|
| Sponges |
|---|
| Genus | Species | Presence | Material | Notes | Images |
|---|
| Clathrodictyon | C. boreale | Fox Point and Chabot members. | "A single small, spheroidal specimen". | A stromatoporoid. | |
| Ecclimadictyon | E. macrotuberculatum | Chabot Member. | | A stromatoporoid. | |
| Pachystylostroma | | Very top of the Chabot Member. | | A stromatoporoid. | |
|
See also
References
Notes and References
- 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 . 10.1127/0078-0421/2014/0040 . 0078-0421.
- Jin . Jisuo . Copper . Paul . Late Ordovician and Early Silurian pentamerid brachiopods of Anticosti Island, Québec, Canada . Palaeontographica Canadiana.
- Ross . June Phillips . 1960 . Larger Cryptostome Bryozoa of the Ordovician and Silurian, Anticosti Island, Canada: Part I . Journal of Paleontology . 34 . 6 . 1057–1076 . 1300852 . 0022-3360.
- Dixon . O. A. . January 1986 . The heliolitid coral Acidolites in Ordovician–Silurian rocks of eastern Canada1 . Journal of Paleontology . en . 60 . 1 . 26–52 . 10.1017/S002233600002148X . 130759173 . 0022-3360.
- Book: Ruedemann, Rudolf . Graptolites of North America . 1947 . Geological Society of America . 978-0-8137-1019-8 . en.
Canada