Council Grove Group

{{Short description|Geologic group in the United States}}

{{Infobox rockunit

| name = Council Grove Group

| image =

| caption =

| type = Group

| age =
Carboniferous-Permian boundary

| period = Early Permian

| prilithology =

| otherlithology =

| namedfor = Council Grove, Kansas

| namedby =

| region = Midcontinent (Kansas, Nebraska, Oklahoma, Colorado (subsurface) )

| country = United States

| coordinates =

| unitof =

| subunits = Speiser Shale

Funston Limestone

Blue Rapids Shale

Crouse Limestone

Easly Creek Shale

Bader Formation

Stearns Shale

Beattie Limestone

Eskridge Shale

Grenola Limestone

Roca Shale

Red Eagle Limestone

Johnson Shale

Foraker Limestone

| underlies = Chase Group

| overlies = Admire Group

| thickness =

| extent =

| area =

| map =

| map_caption =

}}

The Council Grove Group is a geologic group in Kansas, Oklahoma, and Nebraska as well as subsurface Colorado. It preserves fossils dating to the Carboniferous-Permian boundary.{{cite journal |journal= Current Research in Earth Sciences |issue= 1 |date= January 2006

|author= Robert S. Sawin, Ronald R. West, Evan K. Franseen, W. Lynn Watney

|url= https://www.researchgate.net/publication/251528028

|title= Carboniferous-Permian Boundary in Kansas, Midcontinent, U.S.A

|volume= 252 |quote= ... the Carboniferous-Permian boundary in Kansas can now be confidently defined. Based [on fossil changes, the] boundary in Kansas can be placed at the base of the Bennett Shale Member of the Red Eagle Limestone.}}{{cite web | title = Geologic Unit: Council Grove | series = Geolex — Unit Summary | work = National Geologic Database | publisher = United States Geological Survey | url = https://ngmdb.usgs.gov/Geolex/Units/CouncilGrove_7740.html |access-date = 2019-06-02 }} This group forms the foundations and lower ranges of the Flint Hills of Kansas, underlying the Chase Group that forms the highest ridges of the Flint Hills.

The Group particularly consists of megacyclothems alternating between massive mudstone paleosols and massive shallow marine limestone. The sequences of these alternations correlate with the ~400,000 year component of Milankovitch cycles. A number of the limestones have minor flint-filled marine animal burrows, anticipating the massive flint beds of the Chase Group.

With the exposure of the group's lower formations in the 1993 flooding,{{cite journal |author= David Mathews, Vlad G. Perlea, Francke C. Walberg, Douglas R. Anderson (U.S. Army Corps of Engineers, Kansas City, Missouri) |title= Erosion and Repair of Unlined Spillway Chute Excavated in Rock |journal= International Conference on Case Histories in Geotechnical Engineering |date= 1998 |publisher= Missouri University of Science and Technology |access-date = 2019-06-01 |url= https://scholarsmine.mst.edu/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1726&context=icchge }} the entirety of the Council Grove Group, from hillcrest Speiser Shale down to pond-level Americus limestone, is exposed for study from top to bottom in the Tuttle Creek Lake Spillway.{{cite web |url= http://www.kgs.ku.edu/General/Geology/County/nop/pt/pt_11_5.html |title= Pottawatomie County T. 9 S., R. 8 E. |publisher= Kansas Geological Survey |access-date= 2019-06-02 }}