| Four Mile Dam Formation | |
|---|---|
| Stratigraphic range: | |
 Vertebrate remains from the Four Mile Dam Formation. | |
| Type | Geological formation |
| Unit of | Traverse Group [1] |
| Lithology | |
| Primary | Limestone |
| Location | |
| Region |  Michigan |
| Country |  United States |
| Type section | |
| Named by | Cooper & Warthin [2] |
| Year defined | 1941 [2] |
The Four Mile Dam Formation, also called the Four Mile Dam Limestone, is a geologic formation in Michigan. It preserves fossils dating back to the middle Devonian period.
| Acanthodians reported from the Four Mile Dam Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Presence | Material | Notes | Images |
| 'Acanthodii' | Unidentified | "Two partial fin spines (JS 120, JS 121)". [1] | "Distinct from named acanthodians ( Gyracanthus , Machaeracanthus , and Oracanthus ) and chondrichthyans ( Tamiobatis and Acondylacanthus ) reported from Michigan". [1] |  | |
| Conodonts reported from the Four Mile Dam Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Presence | Material | Notes | Images |
| Acodina | A. formosa | [3] | Also found in the Detroit River, Traverse, Dundee, Bell, Alpena and Norway Point formations. | ||
| Belodella | B. devonicus | [3] | Also found in the Detroit River, Traverse, Antrim, Alpena and Norway Point formations. | ||
| Icriodus | I. latericrescens latericrescens | [3] | Also found in the Traverse, Bell, Ferron Point, Genshaw, Newton Creek, Alpena, Norway Point, Potter Farm and Thunder Bay formations. | ||
| Ozarkodina | O. willsi | [3] | Also found in the Detroit River, Traverse, Antrim, Dundee, Alpena and Norway Point formations. | ||
| Polygnathus | P. varcus | [3] | Also found in the Traverse, Antrim, Alpena, Norway Point and Thunder Bay formations. | ||
| Placoderms reported from the Four Mile Dam Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Presence | Material | Notes | Images |
| ?Macropetalichthys | ?M. sp. | "A partial head shield (32M)". [1] | A petalichthyid. |  | |
| ?Mylostoma | ?M. sp. | 39 specimens, including potential juveniles. [1] |  | ||
| 'Placodermi' | Unidentified | "One specimen of an armour plate (JS 4)". [1] |  | ||
| Protitanichthys | P. rockportensis | "One specimen of an armor fragment (JS 101)". [1] | A coccosteid. | ||
Color key
| Notes Uncertain or tentative taxa are in small text; |
| Brachiopods reported from the Four Mile Dam Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Presence | Material | Notes | Images |
| Douvillina | D. distans | Four Mile Dam, Thunder Bay River, Alpena County, Michigan. [4] | Also found in the Hungry Hollow Formation and Logansport Formation. | ||
| Leptalosia | L. radicans | Four Mile Dam, Thunder Bay River, Alpena County, Michigan. [4] | Also found in the Norway Point, Gravel Point, Alpena and Genshaw formations. | ||
| Longispina | L. emmetensis | Dock Street clay member. [4] | Also found in the Alpena Limestone and Gravel Point Formation. | ||
| Megastrophia | M. gibbosa | Four Mile Dam, Thunder Bay River, Alpena County, Michigan. [4] | Also found in the Hungry Hollow Formation and Logansport Formation. | ||
| Oligorhachis | O. oligorhachis | Four Mile Dam, Thunder Bay River, Alpena County, Michigan. [4] | Also found in the Gravel Point Formation. | ||
| Pentamerella | P. alpenensis | Dock Street clay member. [4] | Also found in the Alpena Limestone and Gravel Point Formation. | ||
| P. sp. C | Dock Street clay. [4] | A complete specimen. [4] | |||
| Protoleptostrophia | P. lirella | Dock Street clay member. [4] | Also found in the Norway Point Formation and Alpena Limestone. | ||
| Schuchertella | S. anomala | Possibly the Dock Street clay member. [4] | Also found in the Gravel Point Formation. | ||
| S. sp. | Four Mile Dam, Thunder Bay River, Alpena County, Michigan. [4] | ||||
| Spinulicosta | S. mutocosta | Four Mile Dam, Thunder Bay River, Alpena County, Michigan. [4] | Also found in the Bell, Rockport Quarry, Ferron Point, Beebe School, Thunder Bay and Potter Farm formations. | ||
| Strophodonta | S. erratica | Dock Street clay member. [4] | Also found in the Alpena Limestone and Gravel Point Formation. | ||
| S. fissicosta | Dock Street clay member. [4] | Also found in the upper Gravel Point Formation. | |||
| S. nanus | Dock Street clay member. [4] | Also found in the Alpena Limestone and Gravel Point Formation. | |||
| S. paula | Dock Street clay member. [4] | Also found in the Alpena Limestone. | |||
| S. sp. B | Dock Street clay member and overlying crystalline limestone beds. [4] | Several specimens. [4] | |||
| Rhipidomella | R. penelope traversensis | Thunder Bay River, Alpena County, Michigan. [4] | |||
| Corals reported from the Four Mile Dam Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Presence | Material | Notes | Images |
| Aulocystis | A. cooperi | [5] | Also found in the Plum Brook shale, Silica shale and Potter Farm Formation. | ||
| A. jacksoni | Dock Street clay member. [5] | Also found in the Silica Shale, Ferron Point Formation, Petoskey Formation, Hungry Hollow Formation, Widder Shale, Wanakah shale and Centerfield Limestone. | |||
| Aulopora | A. conferta | [5] | Also found in the Bell, Ferron Point, Gravel Point, Genshaw, Alpena, Potter Farm, Petoskey and Hungry Hollow formations. | ||
| A. gregaria | [5] | Also found in the Genshaw Formation, Alpena Limestone and Petoskey Formation. | |||
| Pachyphragma | P. concentricum | Dock Street clay member. [5] | Also found in the Ferron Point Formation, Gravel Point Formation and Alpena Limestone. | ||
| Gastropods reported from the Four Mile Dam Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Presence | Material | Notes | Images |
| Anematina | A. conica | Upper limestone unit. [2] | An elasmonematid. | ||
| A. mellaria | Upper limestone unit. [2] | An elasmonematid, very rare in the Four Mile Dam Limestone. | |||
| Bembexia | B. (Genuspira) nodosa | Upper limestone unit. [2] | About 35 specimens. [2] | An eotomariid and the most abundant gastropod in the formation. | |
| Dictyobembix | D. bella | Upper limestone unit. [2] | 5 specimens. [2] | An eotomariid. | |
| Mourlonia | M. lirata | Upper limestone unit. [2] | An eotomariid. | ||
| Murchisonia | M. (Murchisonia) subulata | Upper limestone unit. [2] | A murchisoniid, extremely rare in the formation. | ||
| Naticopsis | N. sp. | Upper limestone unit. [2] | A neritopsid, extremely rare in the formation. | ||
| Palaeoscurria? | P.? sp. | Upper limestone unit. [2] | 3 poorly preserved ventral molds. [2] | A metoptomatid. | |
| Platyceras | P. (Platyceras) bartlettense | Dock Street Clay Member. [2] | A platyceratid. | ||
| P. (Euthyrachis) indianense | Dock Street Clay Member. [2] | A platyceratid. | |||
| P. (Orthonychia) variabilis | Upper limestone unit. [2] | A platyceratid. | |||
| Pseudozygopleuridae? Genus A | Genus A sp. A | Upper limestone unit. [2] | Relatively numerous steinkerns. [2] | ||
| Pseudozygopleuridae? Genus B | Genus B sp. B | Upper limestone unit. [2] | One very poorly preserved steinkern with a few small shell patches (YPM 23684). [2] | ||
| Spiroscala | S. sp. | Upper limestone unit. [2] | One specimen (UMMP 47377). [2] | An eotomariid. | |
| Straparollus | S. (Philoxene) sp. | Upper limestone unit. [2] | 3 poorly preserved specimens. [2] | An euomphalid. | |
| Trepospira | T. (Angyomphalus) bella | Upper limestone unit. [2] | A raphistomatid, very rare in the Four Mile Dam Limestone. | ||
| Turbinilopsis | T. anacarina | Upper limestone unit. [2] | Abundant specimens. [2] | An anomphalid. | |
| Sponges reported from the Four Mile Dam Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Presence | Material | Notes | Images |
| Anostylostroma | A. anacolumna | On Thunder Bay River. [6] | A stromatoporoid. | ||
| Trilobites reported from the Four Mile Dam Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Presence | Material | Notes | Images |
| Cordania | C. rara | [7] | |||
| Dechenella | D. (Monodechenella) macrocephala | [7] | Also found in the Hamilton Group. | ||
| D. (Basidechenella) rowi | [7] | Also known from the Hamilton Group. | |||
| Eldredgeops | E. rana | [7] | Originally reported as Phacops rana. Also found in the Hamilton, Hungry Hollow, Widder, Plum Brook, Prout, Ten Mile Creek, Alpena, Norway Point and Gravel Point formations. |  | |
| Greenops | G. aequituberculatus | Dock Street clay member. [7] | Also found in the Norway Point and Gravel Point formations. | ||
| G. traversensis | Dock Street clay member. [7] | Also found in the Gravel Point Formation. | |||
| Phacops | P. rana | [7] | Reassigned to the genus Eldredgeops . | ||
| Proetus | P. (Crassiproetus) traversensis | [7] | Also known from the Gravel Point Formation. | ||
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The Traverse Group is a geologic group in Michigan, Indiana and Ohio comprising middle Devonian limestones with calcareous shale components. Its marine fossils notably include Michigan's state stone, the Petoskey stone, among other corals and records of ancient marine life. A range of trilobites has also been found in the Traverse Group.
The Gravel Point Formation is a geologic formation in western Michigan. It preserves fossils dating back to the middle Devonian period and correlates with the Long Lake Limestone and Alpena Limestone.
The Norway Point Formation is a geologic formation in Michigan. It preserves fossils dating back to the middle Devonian period.
The Thunder Bay Limestone is a geologic formation in Michigan. It preserves fossils dating back to the Devonian period.
The Georgian Bay Formation is a geologic formation in Michigan and Ontario. It preserves fossils dating back to the Ordovician period. The type locality of the formation is on East Meaford Creek, south shore of Nottawasaga Bay, Georgian Bay.
The Ludlowville Formation is a geologic formation in New York, Ohio and Pennsylvania. It dates to the Devonian period.
The Sharps Formation is a geologic formation in South Dakota. It preserves fossils dating back to the Paleogene.
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The Luning Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period.
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The Campbellton Formation is a geologic formation in New Brunswick. It preserves fossils dating back to the latest Pragian and Emsian of the Devonian period.
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