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

Stratigraphy of the Devonian deposits of the northern part of the Lower Peninsula of Michigan, showing the Thunder Bay Limestone[1]
Thunder Bay Limestone | |
---|---|
Stratigraphic range: | |
Type | Geological formation |
Unit of | Traverse Group[1] |
Sub-units | Partidge Point Member, Potter Farm Member, and Norway Point Member |
Underlies | Kettle Point Formation and Squaw Bay Limestone |
Overlies | Potter Farm Formation[1] |
Location | |
Region | ![]() |
Country | ![]() |
Fossil content
Conodonts
Conodonts reported from the Thunder Bay Limestone | |||||
---|---|---|---|---|---|
Genus | Species | Presence | Material | Notes | Images |
Icriodus | I. cymbiformis | [2] | Also found in the Detroit River, Traverse, Antrim, Ferron Point, Genshaw, Alpena and Norway Point formations. | ||
I. expansus | [2] | 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 | [2] | Also found in the Traverse, Bell, Ferron Point, Genshaw, Newton Creek, Alpena, Four Mile Dam,,Norway Point and Potter Farm formations. | |||
Polygnathus | P. varcus | [2] | Also found in the Traverse, Antrim, Alpena, Four Mile Dam and Norway Point formations. | ||
Placoderms
Placoderms reported from the Thunder Bay Limestone | |||||
---|---|---|---|---|---|
Genus | Species | Presence | Material | Notes | Images |
Ptyctodus | P. sp. | "Northeast shore of Partridge Point, 6.4 kilometers south of Alpena".[1] | A tooth plate (UMMP 3023).[1] | A ptyctodontid. | ![]() |
Brachiopods
Brachiopods reported from the Thunder Bay Limestone | |||||
---|---|---|---|---|---|
Genus | Species | Presence | Material | Notes | Images |
Pentamerella | P. proteus | [3] | |||
Spinulicosta | S. mutocosta | [3] | Also found in the Bell, Rockport Quarry, Ferron Point, Four Mile Dam, Beebe School and Potter Farm formations. | ||
Cnidarians
Cnidarians reported from the Thunder Bay Limestone | |||||
---|---|---|---|---|---|
Genus | Species | Presence | Material | Notes | Images |
Syringopora | S. ehlersi | Bluffs on northeast shore of Partridge Point, 4 miles south of Alpena, Alpena County.[4] | A tabulate coral. | ![]() | |
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.[5] | A crinoid. | ||
Gennaeocrinus | G. romingeri | Bluffs on northeast shore of Partridge Point, 4 miles south of Alpena, Alpena County.[5] | A crinoid. | ||
Trilobites
Trilobites reported from the Thunder Bay Limestone | |||||
---|---|---|---|---|---|
Genus | Species | Presence | Material | Notes | Images |
Dechenella | D. (Basidechenella) reimanni | Alpena County, Michigan.[6] | |||
D. (Basidechenella) sp. C | Alpena County, Michigan.[6] | A single specimen.[6] | |||
Dipleura | D. dekayi | Partridge Point on Thunder Bay, about 4 miles south of Alpena.[6] | Also found in the Norway Point Formation. | ![]() | |
Greenops | G. alpenensis | Alpena County, Michigan.[6] | |||
Phacops | P. iowensis | Alpena County, Michigan.[6] | Also found in the Potter Farm and Petoskey formations. | ||
Proetus | P. (Crassiproetus) alpenensis | [6] | Also found in the Potter Farm Formation. | ||
References
- Stack, Jack; Sallan, Lauren (2018-09-20). "An examination of the Devonian fishes of Michigan". PeerJ. 6 (2). doi:10.7717/peerj.5636.
- Orr, R. William (1971). "Conodonts from Middle Devonian Strata from the Michigan Basin".
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(help) - 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".
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: Cite journal requires|journal=
(help) - Watkins, J. Lloyd (1959). "Middle Devonian Auloporid Corals from the Traverse Group of Michigan". Journal of Paleontology. 33 (5): 793–808. ISSN 0022-3360.
- 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. XIX (11): 143–155.
- Stumm, Erwin (1953). "Trilobites of the Devonian Traverse Group of Michigan" (PDF). University of Michigan Press - Museum of Paleontology.
- Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 17 December 2021.
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