Gun River Formation

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

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]

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

• Earth sciences portal
• Canada portal
• Paleontology portal

• List of fossiliferous stratigraphic units in Quebec