Gravel Point Formation

{{Short description|Geological formation}}

{{Infobox rockunit

| name = Gravel Point Formation

| image = Fossiliferous limestone (Gravel Point Formation, Middle Devonian; near South Point, west of Charlevoix, Michigan, USA) 8.jpg

| caption = Fossiliferous limestone from the Gravel Point Formation

| type = Geological formation

| age = {{fossil range|Givetian|Givetian|Middle Devonian (Givetian)}}

| period = Devonian

| prilithology = Limestone

| otherlithology =

| namedfor =

| namedby =

| region = Michigan

| country = United States

| coordinates =

| unitof = Traverse Group

| subunits =

| underlies =

| overlies =

| thickness =

| extent =

| area =

| map =

| map_caption =

}}

The Gravel Point Formation is a geologic formation in western Michigan, United States. It preserves fossils dating back to the middle Devonian period and correlates with the Long Lake Limestone and Alpena Limestone.{{Cite journal |last=Mohan |first=Joseph |date=November 2013 |title=A Paleoenvironmental Analysis of the Middle Devonian Gravel Point Formation, Western Michigan |url=https://www.researchgate.net/publication/297469834 |journal=The Professional Geologist |volume=50 |issue=6 |pages=12–16}}

Description

The Michigan Basin was a shallow marine shelf during the middle Devonian, located between 30º South and 20º North latitude in central Laurasia. According to stratigraphic and paleontological examination, the sediments of the Gravel Point Formation were deposited in a shallow lagoonal reef environment.

Fossil content

=Vertebrates=

==Acanthodians==

class="wikitable" align="center"
colspan="6" align="center" | Acanthodians of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Gyracanthus

|G. sp.

|South Point (Gravel Point), Little Traverse Bay, Charlevoix County.{{Cite journal |last1=Stack |first1=Jack |last2=Sallan |first2=Lauren |date=2018-09-20 |title=An examination of the Devonian fishes of Michigan |url=https://www.researchgate.net/publication/327778213 |journal=PeerJ |volume=6 |issue=2 |pages=e5636 |doi=10.7717/peerj.5636|pmid=30258725 |s2cid=52843222 |doi-access=free |pmc=6151260 }}

|A single specimen (UMMP 1329).

| A gyracanthid.

|File:Gyracanthus NT small.jpg

==Bony fish==

class="wikitable" align="center"
colspan="6" align="center" | Bony fish of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
?Onychodus

|?O. sp.

|South Point (Gravel Point), Little Traverse Bay, Charlevoix County.

|A single specimen (UMMP 14370).

| An onychodontiform.

|File:OnychodusDB15.jpg

==Placoderms==

class="wikitable" align="center"
colspan="6" align="center" | Placoderms of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Holonemiid

|

|South Point (Gravel Point), Little Traverse Bay, Charlevoix County.

|A single specimen (UMMP 3129).

|

|

=Invertebrates=

Several species of ostracods, an unidentified arthropod 'hook', crinoid columnals and several species of polychaetes and scolecodonts are known from the formation.

==Brachiopods==

class="wikitable" align="center"
colspan="6" align="center" | Brachiopods of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Atrypa

|A. corrugata

|

|

|

|

Douvillina

|D. sp.

|Lower part of the formation.

|2 specimens.{{Cite journal |last=Imbrie |first=John |date=1959 |title=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 |hdl=2246/1258 |url=https://digitallibrary.amnh.org/handle/2246/1258 |language=en-US}}

|

|

Heteralosia

|H. sp. B

|

|2 pedicle valves.

|

|

Leptalosia

|L. radicans

|

|

|Also found in the Norway Point, Alpena, Four Mile Dam, Genshaw, Arkona and Hungry Hollow formations.

|

Longispina

|L. emmetensis

|

|

|Also found in the Alpena Limestone and Four Mile Dam Formation.

|

rowspan=2|Mucrospirifer

|M. latus

|

|

|A spiriferid.

|

M. sp.

|

|

|A spiriferid.

|

Oligorhachis

|O. oligorhachis

|

|

|Also found in the Four Mile Dam Formation.

|

rowspan=2|Orthopleura

|O. sp. A

|"Large Atrypa zone".

|One specimen (U.S.N.M. no. 124258).

|

|

O. sp. B

|"Upper Blue shale".

|One specimen (U.S.N.M. no. 124280).

|

|

rowspan="3"|Pentamerella

|P. aftonensis

|Gorbut Member.

|

|

|

P. alpenensis

|

|

|Also found in the Alpena Limestone and Four Mile Dam Formation.

|

P. sp. D

|

|A small collection of large shells (the largest being 38 millimeters).

|

|

Pholidostrophia

|P. geniculata

|

|

|Also found in the Alpena, Widder and Hungry Hollow formations.

|

Pseudoatrypa

|P. keslingi

|

|

|

|

Schuchertella

|S. anomala

|

|

|Possibly also found in the Four Mile Dam Formation.

|

rowspan="6" |Strophodonta

|S. costata

|

|

|A strophomenid.

|

S. cf. S. erotica

|

|

|A strophomenid.

|

S. erratica

|

|

|Also found in the Alpena Limestone and Four Mile Dam Formation.

|

S. fissicosta

|Upper part of the formation.

|

|Also found in the Four Mile Dam Formation.

|

S. nanus

|

|

|Also found in the Alpena Limestone and Four Mile Dam Formation.

|

S. titan titan

|

|

|Also known from the Alpena Limestone.

|

Truncalosia

|T. gibbosa

|

|

|Also found in the Alpena, Genshaw, Norway Point, Petoskey and Potter Farm formations, the Arkona Shale and the Hamilton Group.

|

Tylothyris

|T. subvaricosa

|

|{{Cite journal |last1=Rogers |first1=Frederick S. |last2=Pitrat |first2=Charles W. |date=May 1987 |title=Distribution of Tylothyris (Brachiopoda) and its occurrence in the Traverse Group (Middle Devonian) of Michigan |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/distribution-of-tylothyris-brachiopoda-and-its-occurrence-in-the-traverse-group-middle-devonian-of-michigan/DBF58D3D881A40ECE487E3EA5C448553 |journal=Journal of Paleontology |language=en |volume=61 |issue=3 |pages=494–507 |doi=10.1017/S0022336000028651 |s2cid=130922140 |issn=0022-3360|url-access=subscription }}

|Also found in the Cedar Valley, Milwaukee, Mineola, Bell, Rockport Quarry, Ferron Point, Genshaw, Alpena, Norway Point and Potter Farm formations.

|

==Bryozoans==

class="wikitable" align="center"
colspan="6" align="center" | Bryozoans of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Fenestellapolypore

|F. magnifica

|

|

| A fenestellid.

|

==Cnidarians==

class="wikitable" align="center"
colspan="6" align="center" | Cnidarians of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
rowspan=2|Aulocystis

|A. alectiformis

|

|{{Cite journal |last=Watkins |first=J. Lloyd |date=1959 |title=Middle Devonian Auloporid Corals from the Traverse Group of Michigan |url=https://www.jstor.org/stable/1300915 |journal=Journal of Paleontology |volume=33 |issue=5 |pages=793–808 |jstor=1300915 |issn=0022-3360}}

|Also found in the Alpena Limestone.

|

A. fenestrata

|6 specimens.

|

|Also found in the Alpena Limestone.

|

rowspan="2" |Aulopora

|A. conferta

|

|

|Also found in the Bell, Ferron Point, Genshaw, Alpena, Four Mile Dam, Potter Farm, Petoskey and Hungry Hollow formations.

|

A. socialis

|Upper part of the formation.

|

|

|

Favosites

|F. mammilatus

|

|

| A tabulate coral.

|

rowspan=2|Pachyphragma

|P. concentricum

|

|

|Also found in the Ferron Point, Four Mile Dam and Alpena formations.

|

P. erectum

|

|

|Also found in the Potter Farm and Petoskey formations.

|

==Sponges==

class="wikitable" align="center"
colspan="6" align="center" | Sponges of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Parallelopora

|P. winchelli

|

|

| A stromatoporoid.

|

==Tentaculitans==

class="wikitable" align="center"
colspan="6" align="center" | Tentaculitans of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Tentaculites

|T. sp.

|

|

| A tentaculitid.

|File:TentaculitidDevonian.jpg

==Trilobites==

{{Paleobiota-key-compact}}

class="wikitable" align="center"
colspan="6" align="center" | Trilobites of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Ancyropyge

|A. romingeri

|"Longispina emmetensis zone".{{Cite journal|last=Stumm|first=Erwin|date=1953|title=Trilobites of the Devonian Traverse Group of Michigan|url=https://deepblue.lib.umich.edu/bitstream/handle/2027.42/48269/ID108.pdf?sequence=2|journal=University of Michigan Press - Museum of Paleontology}}

|

|

|

Dechenella

|D. (Basidechenella) pulchra

|

|

|Also found in the Alpena Limestone and Dock Street clay of the Four Mile Dam Formation.

|

Eldredgeops

|E. rana alpenensis

|

|

|Originally reported as Phacops rana alpenensis. Also found in the Alpena Limestone.

|File:Phacops rana.jpg

rowspan=2|Greenops

|G. aequituberculatus

|

|

|Also found in the Norway Point and Four Mile Dam formations.

|

G. traversensis

|

|

|Also found in the Dock Street clay of the Four Mile Dam Formation.

|

style="background:#f3e9f3;" |Phacops

|style="background:#fbdddb;" |P. rana alpenensis

|style="background:#fbdddb;" |

|style="background:#fbdddb;" |

|style="background:#fbdddb;" |Reassigned to the genus Eldredgeops.

|style="background:#fbdddb;" |

Proetus

|P. (Crassiproetus) traversensis

|

|

| Also found in the Four Mile Dam Formation.

|

=Flora=

Algal colonies are known from the formation.

==Acritarchs==

class="wikitable" align="center"
colspan="6" align="center" | Acritarchs of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Lophosphaeridium

|L. sp.

|

|

|

|

Tasmanites

|T. sp.

|

|

|

|

==Plants==

class="wikitable" align="center"
colspan="6" align="center" | Plants of the Gravel Point Formation
GenusSpeciesPresence

!Material

NotesImages
Ancyrospora

|A. sp.

|

|Miospores.

|

|

See also

{{Portal|Earth sciences|Michigan|Paleontology}}

References

{{reflist}}

  • {{cite web|title= Fossilworks: Gateway to the Paleobiology Database|author= ((Various Contributors to the Paleobiology Database))|url= https://www.fossilworks.org|access-date= 17 December 2021|archive-date= 25 March 2022|archive-url= https://web.archive.org/web/20220325060448/http://www.fossilworks.org/cgi-bin/bridge.pl?action=home|url-status= live}}

Category:Devonian Michigan

Category:Devonian southern paleotemperate deposits

Category:Limestone formations of the United States

Category:Long stubs with short prose

{{Michigan-geologic-formation-stub}}