Queenston Shale

Queenston Formation Stratigraphic range: Maysvillian to Richmondian PreЄ Є O S D C P T J K Pg N
Queenston Formation exposed at the Cheltenham Badlands
Type	Geological formation
Underlies	Cataract Group and Clinton Formation
Overlies	Cincinnati Group/Georgian Bay Formation / Carlsbad Formation / Oswego Formation
Thickness	Up to 300 m (980 ft)
Lithology
Primary	Shale
Other	Siltstone, sandstone, limestone, gypsum
Location
Region	Southern Ontario Western New York
Country	Canada  United States
Type section
Named for	Queenston, Ontario
Named by	J. F. Caley
Year defined	1940

The Queenston Formation is a geological formation of Upper Ordovician age (Maysvillian to Richmondian Stage), which outcrops in Ontario, Canada (along the northern and eastern flanks of the Niagara Escarpment, as well as east of Ottawa) and New York, United States (just south of Lake Ontario). A typical outcrop of the formation is exposed at Bronte Creek just south of the Queen Elizabeth Way. The formation is a part of the Queenston Delta clastic wedge, formed as an erosional response to the Taconic Orogeny. Lithologically, the formation is dominated by red and grey shales with thin siltstone, limestone and sandstone interlayers. As materials, comprising the clastic wedge, become coarser in close proximity to the Taconic source rocks, siltstone and sandstone layers are predominant in New York.

The formation is wedge-shaped, thick (up to 300 metres (980 ft) below Lake Erie), and laterally extensive, outcropping from Western New York to Cabot Head. It thins from southeast to northwest at around 0.6 metres per kilometre and has a dip of 3° to the south-southwest.

The formation is the topmost Ordovician layer in Southern Ontario and is unconformably overlain by the Lower Silurian rocks of the Cataract Group. At its base it has a conformable gradational contact with underlying beds of the Georgian Bay Formation in Southern Ontario, the Carlsbad Formation near Ottawa, and the Oswego Formation in New York.