Gun River Formation

Gun River Formation
Stratigraphic range: Early Silurian (Llandovery)
Type	Geological formation
Sub-units	Lachute Member Innomée Member Sandtop Member Macgilvray Member
Underlies	Menier Formation[1]
Overlies	Merrimack Formation[1]
Thickness	85 to 100 meters[1]
Location
Region	Quebec
Country	Canada
Type section
Named by	Schuchert and Twenhofel[1]
Year defined	1910[1]

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

Description

The formation is divided into 4 members (from the base up): the Lachute, Innommée, Sandtop and Macgilvray members. The formation was deposited some 40–80 km offshore from the stable Laurentian craton, underwater at depths of 30 to 60 meters.[1]

Fossil content

Vertebrates

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Conodonts
Genus	Species	Presence	Material	Notes	Images
Anticostiodus	A. fahraeusi	Anticosti Island.[2]
	A. boltoni	Anticosti Island.[2]
Icriodella	I. deflecta			Probably instead belongs to the Jupiter Formation.[1]

Invertebrates

Brachiopods
Genus	Species	Presence	Material	Notes	Images
Brachyprion		Sandtop and Macgilvray Members.[1]		A strophomenid.
Coolinia		Sandtop and Macgilvray Members.[1]
Fenestrirostra	F. glacialis	Lowermost part of the formation.[3]		A rhynchonellidalso found in the Merrimack Formation.
	F. pyrrha	Lachute Member.[1]		A rhynchonellid.
'Gotatrypa'	'G.' sp.	Innommée Member.[1]
Hyattidina		Sandtop to Macgilvray Members.[1]		An athyrid.
Joviatrypa		Uppermost Macgilvray Member.[1]
Kulumbella	K. xacta	Upper Macgilvray Member.[4][5]		A pentamerid.
Mendacella		Innommée Member.[1]		A dalmanellid.
Meristina		Innommée Member.[1]
Pentamerus	P. palaformis	Top of the formation (uppermost Macgilvray Member).[1][4]		Also found in the Jupiter Formation.
Stegerhynchus		[1]
Stricklandia	S. gwelani	Top of the formation (Macgilvray Member).[1][4]		Also found in the Jupiter Formation.
	S. sp.	Innommée Member.[4]	A509 (7 broken valves on a slab).[4]	Also found in the uppermost Merrimack Formation.
Sypharatrypa	S. sp.	Innommée Member.[1]

Bryozoans
Genus	Species	Presence	Material	Notes	Images
Phaenopora	P. superba			Also found in the Becscie Formation.[6]
Ptilodictya	P. canadensis		USNM 143039.[6]
	P. sulcata		USNM 143039, 143050; YPM 3063/98, 3063/104.[6]

Corals
Genus	Species	Presence	Material	Notes	Images
Acidolites	A. arctatus	[7]		A heliolitid.
Brachyelasma		[1]
Crassilasma		[1]
Helicelasma		[1]
Palaearaea		Cap aux Goélands (Uppermost Macgilvray Member).[1]	Small colonies.[1]	The only rugosan coral known from the formation, also found in the Menier formation.
Paleofavosites	P. capax		Multiple colonies.[8]	A tabulate coral.

Crinoids
Genus	Species	Presence	Material	Notes	Images
Dendrocrinus		[1]
Eumyelodactylus		Macgilvray Member.[1]
Laurocrinus		Macgilvray Member.[1]
Stupatocrinus		Macgilvray Member.[1]

Graptolites
Genus	Species	Presence	Material	Notes	Images
Paraclimacograptus	P. cf. innuitus	Deeper water facies of the Sandtop Member.[1]

Sponges
Genus	Species	Presence	Material	Notes	Images
Camptodictyon		[1]		A stromatoporoid.
Clathrodictyon		[1]		A stromatoporoid.

See also

• List of fossiliferous stratigraphic units in Quebec

References

1. Copper, Paul; Long, Darrel G. F.; Jin, Jisuo (2012). "The Early Silurian Gun River Formation of Anticosti Island, eastern Canada: A key section for the mid-Llandovery of North America". Newsletters on Stratigraphy. 45 (3): 263. doi:10.1127/0078-0421/2012/0024. ISSN 0078-0421.
2. Zhang, Shunxin; Barnes, Christopher R. (July 2000). "Anticostiodus, a new multielement conodont genus from the Lower Silurian, Anticosti Island, Quebec". Journal of Paleontology. 74 (4): 662–669. doi:10.1666/0022-3360(2000)074<0662:AANMCG>2.0.CO;2. ISSN 0022-3360. S2CID 59056082.
3. Jin, Jisuo; Caldwell, W. G. E.; Copper, Paul (March 1990). "Evolution of the Early Silurian rhynchonellid brachiopod Fenestrirostra in the Anticosti Basin of Quebec". Journal of Paleontology. 64 (2): 214–222. doi:10.1017/s0022336000018370. ISSN 0022-3360. S2CID 132248649.
4. Jin, Jisuo; Copper, Paul. "Late Ordovician and Early Silurian pentamerid brachiopods of Anticosti Island, Québec, Canada". Palaeontographica Canadiana.
5. Jin, Jisuo; Copper, Paul (May 1998). "Kulumbella and Microcardinalia (Chiastodoca) new subgenus, Early Silurian divaricate stricklandiid brachiopods from Anticosti Island, eastern Canada". Journal of Paleontology. 72 (3): 441–453. doi:10.1017/s0022336000024185. ISSN 0022-3360. S2CID 132809506.
6. "Larger Cryptostome Bryozoa of the Ordovician and Silurian, Anticosti Island, Canada". www.jstor.org. SEPM Society for Sedimentary Geology. JSTOR 1300852. Retrieved 2022-09-18.
7. 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.
8. Lee, Dong-Jin; Noble, James P. A. (July 1990). "Reproduction and life strategies in the Paleozoic tabulate coral Paleofavosites capax (Billings)". Lethaia. 23 (3): 257–272. doi:10.1111/j.1502-3931.1990.tb01452.x. ISSN 0024-1164.

• Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Archived from the original on 25 March 2022. Retrieved 17 December 2021.