Embayment Megagroup

Stratigraphic range: Eocene–Cretaceous
Type| Mega Group
Sub-units|

* Mounds Gravel, Grover Gravel
* Wilcox Formation
* Porters Creek Formation
* Clayton Formation
* Owl Creek Formation
* McNairy Formation
* Post Creek Formation

Thickness| upto ~1000'
Lithology
Primary| Sandstone, Clay
Other| Siltstone, Lignite
Location
Region|

* Alabama
* Arkansas
* Illinois
* Kentucky
* Mississippi
* Missouri
* Tennessee

Country|  United States
Extent| Gulf Coast Plain to Southern Illinois

The Embayment Mega Group is found from the Gulf of Mexico north to southern Illinois.

## Stratigraphy

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### Mounds Gravel

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The Mounds Gravel is found in southern Illinois. It is composed of chert and quarts pebbles.[1]

### Grover Gravel

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The Grover Gravel (Rubey, 1952) is found in western Illinois. Named for Grover, Missouri. It is composed of chert pebbles, quartz pebbles, as well as a matrix of quartz sand.[1]

### Willcox Formation

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The Wilcox Formation is a sand formation that is part of the Embayment Megagroup. It runs from southern Illinois to the State of Mississippi. It thickens moving southward, starting at about ~20' thick in outcrops in Illinois to 250' thick in Mississippi.[2]

### Porters Creek Formation

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The Porters Creek is found in southern Illinois. It is massive in nature and lacks bedding or has weak bedding surfaces. it is composed of over 80 percent montmorillonite. This clay is mined commercially in Pulaski County, Illinois.

### Clayton Formation

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The Clayton Formation is made up of clay. The clay is green to buff in color and is silty throughout. At the formation's base it becomes sandy with pebbles. The pebbles are made of chert and are black or white in color.[2]

### Owl Creek Formation

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The Owl Creek Formation is a geologic formation ranging from Tennessee to Mississippi. It preserves fossils dating back to the Cretaceous period. Ornithomimids and ceratopsid remains are known from the formation. The ceratopsid tooth could represent a chasmosaurine.[3]

### McNairy Formation

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The McNairy Formation was formed as a deltaic deposit. The upper and lower parts consists of cross-bedded white to light grey micaceous sand. The middle section is made up of grey to blackish silt, with beds of lignite. This formation is up to 450'.[2]

### Post Creek Formation

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The Post Creek Formation was once called the Tuscaloosa Formation. It has been renamed due to inconsistencies with dating the formation. It is composed of chert gravel and has moderate cementations by silica or kaolinite.[4]

### Baylis Formation

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The Baylis Formation is Cretaceous in age and found in the western sections of the Embayment Megagroup. It rests unconformably on Carboniferous age rock. It is composed of medium to fine grained quartz sand. The upper part of the formation is the Kiser Creek Member. It also contains lenses that may contain, clay, silt and pebbles. The lower member is the Hadley Gravel Member and contains mostly pebbles.[2]

## References

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1. ^ a b Willman, H. B., and John C. Frye, 1970, Pleistocene Stratigraphy of Illinois: Illinois State Geological Survey Bulletin 94, 204 p.
2. ^ a b c d Willman, H. B., Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, and Jack A. Simon, 1975, Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p.
3. ^ Farke, Andrew A.; Phillips, George E. (2017-05-23). "The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA)". PeerJ. 5: e3342. doi:10.7717/peerj.3342. ISSN 2167-8359. PMC 5444368.
4. ^ Harrison, Richard W. and Ronald J. Litwin, 1997, Campanian coastal plain sediments in southeastern Missouri and southern Illinois— significance to the early geologic history of the northern Mississippi Embayment: Cretaceous Research 18, no. 5, p. 687-696.

## Further reading

[edit]

* "ILSTRAT". ilstratwiki.web.illinois.edu. Retrieved 23 March 2024.

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Chronostratigraphy of Alabama

Ph|

| Pz|

| C|

| ⁋|

* Pottsville Formation

|

* Bangor Limestone
* Fort Payne Chert
* Hartselle Sandstone
* Lewis Limestone
* Parkwood Formation
* Pride Mountain Shale
* Tuscumbia Limestone

* Chattanooga Shale

* Red Mountain Formation

* Chepultepec Formation
* Sequatchie Formation
* Stones River Group

* Copper Ridge Dolomite

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Chronostratigraphy of Illinois

Ph|

| Cz|

| Q|

| Holocene|

* Glacial alluvium, drift, and loess

|

Pleistocene|

Embayment Megagroup

* Mounds Gravel
* Grover Gravel

| Pliocene|

Embayment Megagroup

* Mounds Gravel
* Grover Gravel

|

Pe|

| Eocene|

Embayment Megagroup

* Wilcox Formation
* Claiborne Formation

|

Paleocene|

Embayment Megagroup

* Porters Creek Formation
* Clayton Formation

Mz|

| K|

| Upper|

| Maastrichtian|

Embayment Megagroup

* Owl Creek Formation
* McNairy Formation
* Baylis Formation

|

Campanian|

Embayment Megagroup

* Post Creek Formation
* Baylis Formation

Pz|

| C|

| ⁋|

| Kasimovian|

McLeansboro Group

* Bond Formation
* Mattoon Formation
* Patoka Formation
* Shelburn Formation

|

Moscovian|

* Carbondale Group

Bashkirian|

Raccoon Creek Group

* Brazil Formation
* Caseyville Formation
* Mansfield Formation
* Tradewater Formation
* Staunton Formation

| Serpukhovian|

Pope Mega Group

*     Grove Church
Kinkaid Limestone
Dagonia Sandstone
Clore Formation
Palestine Sandstone
Menard Limestone
Waltersburg Formation
Vianna Formation
Tar Springs Sandstone

|

Viséan|

Pope Mega Group

*     Glen Dean Limestone
Hardinsburg Sandstone
Haney Limestone
Fraileys Formation
Beech Creek Limestone
Cypress Sandstone
Ridenhower Formation
Bethel Sandstone
Downeys Bluff Limestone
Yankeetown Limestone
Renault Limestone
Aux Vases Sandstone
Ste. Genevieve Limestone

* Golconda Formation
* Paint Creek Formation
* Paoli Formation

Tournaisian|

* Borden Siltstone
* Chouteau Limestone
* Fern Glen Formation
* Meppen Limestone
* New Albany Formation
* Springville Shale

* Borden Siltstone
* Burlington Limestone
* Fort Payne Formation
* Keokuk Limestone
* Salem Limestone
* St. Louis Limestone
* Ullin Limestone
* Warsaw Formation

| Upper|

| Famennian|

* New Albany Shale

|

Frasnian|

* New Albany Shale

Middle|

| Givetian|

* Cedar Valley Limestone
* St. Laurent Formation

|

Eifelian|

* Grand Tower Limestone
* Wapsinicon Limestone
* Detroit River Formation

Muscatatuck Group

*     North Vernon Limestone
Jeffersonville Limestone

Lower|

| Emsian|

New Harmony Group

*     Clear Creek Chert
Clear Creek Formation

|

Pragian|

New Harmony Group

*     Backbone Limestone

Hunton Megagroup

*     Backbone Limestone
Grassy Knob Chert
Bailey Limestone

| Ludlow|

| Ludfordian|

Hunton Megagroup

* Moccasin Springs Formation
* Racine Dolomite

|

Gorstian|

Hunton Megagroup

* Moccasin Springs Formation
* Racine Dolomite

Wenlock|

| Homerian|

* Sugar Run Dolomite

|

Sheinwoodian|

Hunton Megagroup

* Joliet Dolomite
* St. Clair Limestone

* Marcus Dolomite

Llandovery|

| Telychian|

Hunton Megagroup

* Sexton Creek Limestone

* Marcus Dolomite

|

Aeronian|

Hunton Megagroup

* Sexton Creek Limestone

Rhuddanian|

* Bowling Green Dolomite
* Brainard Shale
* Fort Atkinson Limestone
* Neda Formation

* Blanding Dolomite

Hunton Megagroup

* Kankakee Dolomite

* Mosalem Formation
* Sweeney Dolomite
* Tete des Morts Dolomite

| Upper|

| Hirnantian|

* Leemon Formation

|

Sandbian|

* St. Peter Sandstone

* Cape Limestone
* Decorah Formation
* Dubuque Formation
* Dunleith Formation
* Glenwood Formation
* Grand Detour Formation
* Joachim Dolomite
* Kimmswick Limestone
* Maquoketa Formation
* Mifflin Formation
* Nachusa Formation
* Quimbys Mill Formation
* Scales Shale
* Wise Lake Formation

Middle|

| Darriwilian|

* Dutchtown Limestone
* St. Peter Sandstone

|

* Everton Formation
* Pecatonica Formation
* Plattin Limestone

Lower|

| Tremadocian|

* New Richmond Sandstone
* Oneota Dolomite
* Shakopee Dolomite

|

* Bonneterre Formation

Munising Group

* Davis Formation
* Franconia Formation
* Ironton Sandstone
* Galesville Sandstone
* Eau Claire Formation

* Potosi Dolomite
* Derby-Doerun Formation
* Eminence Dolomite
* Jordan Sandstone
* Mt. Simon Sandstone

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Chronostratigraphy of Kentucky

Ph|

| Pz|

| C|

| M|

| Viséan|

* Paoli Formation

|

| Upper|

* New Albany Shale
* Ohio Shale
* Chattanooga Shale

|

Middle|

* Sellersburg Limestone
* Jeffersonville Limestone
* Boyle Formation

Lower|

* Clear Creek Formation
* Back Bone Formation
* Grassy Knob Formation
* Flat Gap Formation
* Onondaga Limestone
* Oriskany Formation
* Helderburg Group

| Ludlow|

| Ludfordian|

* Louisville Limestone

|

Gorstian|

* Louisville Limestone

Wenlock|

| Homerian|

* Laurel Formation
* Louisville Limestone
* Waldron Shale

|

Sheinwoodian|

* Bisher Formation
* Laurel Formation
* Osgood Formation

Llandovery|

| Telychian|

* Alger Shale
* Brassfield Formation
* Crab Orchard Formation
* Drowning Creek Formation
* Noland Formation
* Osgood Formation

|

Aeronian|

* Brassfield Formation
* Crab Orchard Formation
* Drowning Creek Formation
* Noland Formation

Rhuddanian|

* Brassfield Formation
* Drowning Creek Formation

| Upper|

| Katian|

* Kope Formation
* Lexington Limestone

|

Sandbian|

* Lexington Limestone
* Tyrone Formation

* Maquoketa Shale

Middle|

| Darriwilian|

* St. Peter Sandstone
* Wells Creek Formation

|

Lower|

| Tremadocian|

* Gunter Sandstone

|

| Furongian|

| Paibian|

* Eau Claire Formation
* Mt. Simon Sandstone

|

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Cretaceous Period

| Lower/Early Cretaceous| Upper/Late Cretaceous

|

* Berriasian
* Valanginian
* Hauterivian
* Barremian
* Aptian
* Albian

* Cenomanian
* Turonian
* Coniacian
* Santonian
* Campanian
* Maastrichtian

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