Painted Hills is one of the three units of the John Day Fossil Beds National Monument

John Day Fossil Beds National Monument

John Day Fossil Beds National Monument is a U.S. National Monument in Wheeler and Grant counties in east-central Oregon. Located within the John Day River basin and managed by the National Park Service, the park is known for its well-preserved layers of fossil plants and mammals that lived in the...

, located in Wheeler County, Oregon

Wheeler County, Oregon

As of the census of 2000, there were 1,547 people, 653 households, and 444 families residing in the county. The population density was 1 people per square mile . There were 842 housing units at an average density of 0 per square mile...

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It totals 3132 acres (1,267.5 ha) and is located 9 miles (14.5 km) northwest of Mitchell, Oregon

Mitchell, Oregon

-Demographics:As of the census of 2000, there were 170 people, 75 households, and 42 families residing in the city. The population density was 144.6 people per square mile . There were 91 housing units at an average density of 77.4 per square mile...

 and 75 miles (120.7 km) east of Bend

Bend, Oregon

Bend is a city in and the county seat of Deschutes County, Oregon, United States, and the principal city of the Bend, Oregon Metropolitan Statistical Area. Bend is Central Oregon's largest city, and, despite its modest size, is the de facto metropolis of the region, owing to the low population...

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Painted Hills is named after the colorful layers of its hills corresponding to various geological eras, formed when the area was an ancient river floodplain.

The black soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 is lignite

Lignite

Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...

 that was vegetative matter that grew along the floodplain. The grey coloring is mudstone

Mudstone

Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...

, siltstone

Siltstone

Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...

, and shale

Shale

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

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The red coloring is laterite

Laterite

Laterites are soil types rich in iron and aluminium, formed in hot and wet tropical areas. Nearly all laterites are rusty-red because of iron oxides. They develop by intensive and long-lasting weathering of the underlying parent rock...

soil that formed by floodplain deposits when the area was warm and humid.

An abundance of fossil remains of early horses, camels, and rhinoceroses in the Painted Hills unit makes the area particularly important to vertebrate paleontologists.