| Ringold Formation | |
|---|---|
| Stratigraphic range:Neogene | |
 TheColumbia River flowing through the Ringold Formation. | |
| Type | Formation |
| Underlies | Deposits fromMissoula Floods[1] |
| Overlies | Columbia River Basalt Group |
| Thickness | 1,000 feet (300 m)[2] |
| Location | |
| Coordinates | 46°40′01″N119°26′10″W / 46.667°N 119.436°W /46.667; -119.436[3] |
| Region | Washington (state) |
| Country | United States |
| Type section | |
| Named for | Ringold Post Office[4] |
| Named by | John C. Merriam, John P. Buwalda[5] |
TheRingold Formation is ageologic formation in EasternWashington, United States. The formation consists of sediment laid down by theColumbia River following theflood basalt eruptions of theColumbia River Basalt Group, and reaches up to 1,000 feet (300 m) thick in places.[6][2] It preservesfossils dating back to theNeogeneperiod.[7]
Exposures of the Ringold Formation can be found fromHanford Reach National Monument north to theMoses Lake area.[5] Large portions of the formation are buried by other sediment deposits, extending as far asWallula Gap southeast ofKennewick.[8] In recent years, irrigation water entering the groundwater system has destabilized some Ringold Formation slopes and cliffs, causing landslides.[9] The formation was named in 1917 for a school of the same name that existed at the time. Ringold School was located on theFranklin County side of the Columbia River to the south ofSavage Island.[4][10]
During the flood basalt eruptions before the sediments were laid down, the Columbia River followed a different route than it does today, taking it near the present-day sites ofYakima andGoldendale. North-to-south compression of theColumbia Plateau caused anticline folds likeRattlesnake Mountain and theHorse Heaven Hills to rise. These ridges provided geographic barriers, rerouting the river eastward toward theTri-Cities with it eventually flowing through Wallula Gap. The Ringold Formation is the sediment laid down after this course change took place.
Some of the sediments found as part of the formation may have been sourced from ancestral versions of otherPacific Northwest rivers like theClearwater andPend Oreille.[2] Layers of volcanic ash can also be found, with thicknesses ranging from being barely noticeable to 4 feet (1.2 m) thick.[8]
The Ringold Formation represents sand and gravel placed by the Columbia River between 9 and 3 million years ago. These deposits overlay cooled lava erupted as part of the Columbia River Basalt Group, a type of volcanic eruption known asflood basalts erupting from fissures across eastern Washington and Oregon that were unrelated to theCascade Range.[11] It is covered in places by deposits from theMissoula Floods.
Regional uplift caused the Columbia toerode parts of the Ringold Formation. The White Bluffs on the Hanford Reach National Monument is a significant example of this.[6]
Landslides along the Columbia River have increased in recent years due to irrigation aroundBasin City andOthello. Irrigation water enters and flows through thegroundwater system toward the river easily through deposits left by the Missoula Floods. This destabilizes Ringold Formation features like the White Bluffs, causing the landslides.[9] Landslides did not occur frequently before 1960. Rapid changes in river flow caused by thePriest Rapids Dam upstream may also contribute to slope destabilization.[12]
The largest landslide in the White Bluffs portion of the formation is adjacent toLocke Island. This complex, initiated in the 1970s, has rerouted the Columbia River. As a result of the change, criticalsalmon spawning habitat has been destroyed. The landslide restricts the flow of the river on the east side of the river and as a result, large portions of Locke Island are being removed by the Columbia River. Movement of this landslide is ongoing, but the primary factor behind the continued movement is destabilization by the Columbia River eroding the fallen material. Blown sand from this landslide is the primary source material forsand dunes atop the bluffs near the island.[13][9]
The Locke Island slide is the northernmost slide along the White Bluffs. There are at least five other major slides into the Columbia River, with the southernmost one being across the river fromPacific Northwest National Laboratory in north Richland, which occurred in 2008. At least one slide has occurred in nearbycoulees.[12]
The sediments include fossils from theMiocene. Along the Columbia River, fossilized remains ofrhinoceros andsalmonoid fish. The largest diversity of remains have been found among the White Bluffs, which are an exposed portion of the uppermost part of the formation. In addition to those that were discovered along the river, there are 27 additional species. These include smaller animals such as frogs, lizards, andring-tailed cats, as well as larger ones like horses, mastodons, and camels. Petrified wood can be found nearby.[2] Analysis of late Miocene to early Pliocene fossils of ringtails suggests the area was once a much milder, but seasonal climate.[14]
Several unique specimens have been found in the formation. An excavation done for a basement nearBadger Mountain inRichland unearthed the northwesternmost example found thus far ofAphelops. This is also the only confirmed specimen of Aphelops in Washington.[15]
