Thunder Bay Limestone Explained

Thunder Bay Limestone
Type:	Geological formation
Period:	Devonian
Unitof:	Traverse Group
Subunits:	Partidge Point Member, Potter Farm Member, and Norway Point Member
Underlies:	Kettle Point Formation and Squaw Bay Limestone
Overlies:	Potter Farm Formation

The Thunder Bay Limestone is a geologic formation in Michigan. It preserves fossils dating back to the Devonian period.

Fossil content

Vertebrates

Conodonts

Conodonts reported from the Thunder Bay Limestone
Genus	Species	Presence	Material	Notes	Images
Icriodus	I. cymbiformis		^[1]	Also found in the Detroit River, Traverse, Antrim, Ferron Point, Genshaw, Alpena and Norway Point formations.
	I. expansus			Also found in the Detroit River, Traverse, Antrim, Lucas, Anderdon, Dundee, Bell, Ferron Point, Genshaw, Alpena, Potter Farm and Norway Point formations.
	I. latericrescens latericrescens			Also found in the Traverse, Bell, Ferron Point, Genshaw, Newton Creek, Alpena, Four Mile Dam,,Norway Point and Potter Farm formations.
Polygnathus	P. varcus			Also found in the Traverse, Antrim, Alpena, Four Mile Dam and Norway Point formations.

Placoderms

Invertebrates

Brachiopods

Brachiopods reported from the Thunder Bay Limestone
Genus	Species	Presence	Material	Notes	Images
Pentamerella	P. proteus		^[2]
Spinulicosta	S. mutocosta			Also found in the Bell, Rockport Quarry, Ferron Point, Four Mile Dam, Beebe School and Potter Farm formations.

Echinoderms

Echinoderms reported from Thunder Bay Limestone
Genus	Species	Presence	Material	Notes	Images
Corocrinus	C. pettyesi	Bluffs on northeast shore of Partridge Point, 4 miles south of Alpena, Alpena County.^[4]		A crinoid.
Gennaeocrinus	G. romingeri	Bluffs on northeast shore of Partridge Point, 4 miles south of Alpena, Alpena County.		A crinoid.

Trilobites

Trilobites reported from the Thunder Bay Limestone
Genus	Species	Presence	Material	Notes	Images
Dechenella	D. (Basidechenella) reimanni	Alpena County, Michigan.^[5]
	D. (Basidechenella) sp. C	Alpena County, Michigan.	A single specimen.
Dipleura	D. dekayi	Partridge Point on Thunder Bay, about 4 miles south of Alpena.		Also found in the Norway Point Formation.
Greenops	G. alpenensis	Alpena County, Michigan.
Phacops	P. iowensis	Alpena County, Michigan.		Also found in the Potter Farm and Petoskey formations.
Proetus	P. (Crassiproetus) alpenensis			Also found in the Potter Farm Formation.

See also

• List of fossiliferous stratigraphic units in Michigan

References

• Web site: Fossilworks: Gateway to the Paleobiology Database. ((Various Contributors to the Paleobiology Database)). 17 December 2021.

Notes and References

1. Orr . R. William . 1971 . Conodonts from Middle Devonian Strata from the Michigan Basin . en-US.
2. Imbrie . John . 1959 . Brachiopods of the Traverse group (Devonian) of Michigan. Part 1, Dalmanellacea, Pentameracea, Strophomenacea, Orthotetacea, Chonetacea, and Productacea. Bulletin of the AMNH; v. 116, article 4 . en-US.
3. Watkins . J. Lloyd . 1959 . Middle Devonian Auloporid Corals from the Traverse Group of Michigan . Journal of Paleontology . 33 . 5 . 793–808 . 0022-3360.
4. Kesling . Robert V. . 1964 . Two New Crinoids of the Family Periechocrinitidae from the Middle Devonian Thunder Bay Limestone of Michigan . Contributions from the Museum of Paleontology, University of Michigan . en-US . XIX . 11 . 143–155.
5. Stumm. Erwin. 1953. Trilobites of the Devonian Traverse Group of Michigan. University of Michigan Press - Museum of Paleontology.