Chalk Butte Formation

{{Infobox rockunit

| name = Chalk Butte Formation

| image =

| caption =

| type = Formation

| age = Tortonian-Zanclean (Hemphillian)
~{{fossil range|10.3|4.9}}

| period = Messinian

| prilithology =Tuffaceous sandstones, siltstones, conglomerates

| otherlithology =Tuff, ash beds, freshwater limestone

| namedfor = Chalk Butte

| namedby =

| region = Malheur County, Oregon

| country = {{USA}}

| coordinates = {{coord|43.6|N|117.5|W|display=inline,title}}

| paleocoordinates = {{coord|44.3|N|114.6|W|display=inline}}

| unitof =

| subunits =

| underlies =

| overlies =

| thickness =About 538 feet

| extent =

| area =

| map = {{Location map+ | United States#Oregon

| relief = 1

| width = 250

| float = center

| places =

{{Location map~ | United States#Oregon

| lat_deg = 43.6

| lon_deg = -117.5

| mark = Yellow ffff80 pog.svg

| marksize = 12

}}

}}

| map_caption =

}}

The Chalk Butte Formation is a geologic formation in Oregon, which forms a part of the Idaho Group.[https://ngmdb.usgs.gov/Geolex/Units/ChalkButte_4967.html Chalk Butte Formation] at USGS It preserves fossils dating back to the Neogene period.[https://paleobiodb.org/classic/displayStrata?geological_group=&formation=Chalk%20Butte&group_formation_member=Chalk%20Butte Chalk Butte Formation] at Fossilworks.org It was proposed along with the Grassy Mountain Basalt Formation and the Kern Basin Formation as a division of the Idaho Group rocks in the Mitchell Butte Quadrangle.{{Cite magazine |last=Corcoran |first=R. E. |last2=Doak |first2=R. A. |last3=Porter |first3=P. W. |last4=Pritchett |first4=F. I. |last5=Privrasky |first5=N. C. |date=1962 |title=Geology of the Mitchell Butte Quadrangle, Oregon |url=https://pubs.oregon.gov/dogami/gms/GMS-002.pdf |access-date=26 June 2024 |magazine=Geological Map Series |publisher=State of Oregon Department of Geology and Mineral Industries |location=Portland, Oregon}} The predominant rock types are tuffaceous sandstones, siltstones, and conglomerates with smaller amounts of tuff, ash beds, and freshwater limestone. A partial section at the type location determined the formation to be about 538 feet thick.