Gull River Formation

The Gull River Formation is a geological formation of Middle Ordovician age (Caradoc Stage), which outcrops in Ontario, Canada.^[1] Lithologically, the formation is dominated by light grey to brown limestones and greenish gray dolomites with thin shale and sandstone interlayers.^[2][3]

Gull River Formation
Stratigraphic range: Caradoc ~460.9–449 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Gull River Formation exposed along the shore of Lake St. John, Ramara
Type	Formation
Unit of	Simcoe Group Black River Group
Underlies	Bobcaygeon Formation Coboconk Formation
Overlies	Shadow Lake Formation
Lithology
Primary	Limestone, dolomite
Other	Shale, sandstone
Location
Region	Ontario New York Pennsylvania
Country	Canada United States
Type section
Named for	Gull River
Named by	V. J. Okulitch
Year defined	1939

Fossil content

Invertebrates

Chelicerates

Chelicerates reported from the Gull River Formation
Genus	Species	Presence	Material	Notes	Images
Lunataspis	L. borealis	Upper Member, Kingston, Ontario.[4]	3 specimens (1 adult & 2 juveniles or subadults).[4]	A horseshoe crab.

Flora

Acritarchs

Acritarchs reported from the Gull River Formation
Genus	Species	Presence	Material	Notes	Images
Dicommopalla	D. rissae	Southern Ontario.[5]		Also found in the Bobcaygeon Formation.