Rosebud Formation

{{Short description|Geological formation in midwestern US}}

{{Infobox rockunit

| name = Rosebud Formation

| image = File:Natural seeps PA120590.jpg

| caption =

Along the north banks of the Niobrara River in northern Nebraska, the pink of the Rosebud Formation is commonly seen with many seeps, trickles, and waterfalls emitting from the Ogallala Aquifer in the overlying Valentine Formation

| type = Formation

| age = {{fossilrange|Miocene}}

| period = Miocene

| prilithology = pink siltstone

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| region = Nebraska, South Dakota

| country = United States

| coordinates =

| unitof = Arikaree Group

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| underlies = Valentine Formation

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The Rosebud Formation is a geologic formation of cemented pink silt in Nebraska and South Dakota, dating to the early middle Miocene epoch of the Neogene period.{{cite web | title = Geologic Unit: Rosebud | series = Geolex — Significant Publications | work = National Geologic Database |publisher = United States Geological Survey | url = https://ngmdb.usgs.gov/Geolex/UnitRefs/RosebudRefs_10238.html | access-date = 2024-02-24 }} Possibly named for its color, no type location has been set for this unit, but it is associated with the Valentine Formation along the Niobrara River. The fine silt of the formation forms an aquitard beneath the Ogallala Aquifer carried by the Valentine Formation. Many springs from the Valentine sands flow down the Rosebud outcrop into the Niobrara River.{{cite web |title= Geologic Formations |website= Niobrara National Scenic River |publisher= National Park Service |url= https://www.nps.gov/niob/learn/nature/geologicformations.htm |access-date=2024-02-24 |quote= A finer-grained siltstone, the reddish-hued Rosebud forms the "floor" of the Ogallala aquifer. Water cannot seep into the rock as easily as it can in the Valentine, and a stream cannot cut down through it as quickly. There are more than 200 spring-fed waterfalls found along the scenic portion of the river, and most are "held up" by the Rosebud formation. }}