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Latah Formation

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Latah Formation
Stratigraphic range: 21.3–12.1 Ma Early to Middle Miocene
TypeGeological formation
Sub-unitsClarkia fossil beds
UnderliesColumbia River Basalts
OverliesColumbia River Basalts
Area175 miles (282 km) by 75 miles (121 km)
Thicknessup to 300 ft (91 m)
Lithology
Primaryshales
Othergravels, ashes
Location
LocationEastern Washington, northwestern Idaho, & northeastern Oregon
RegionPacific Northwest
CountryUnited States
ExtentColumbia Plateau
Type section
Named byPardee & Kirk Bryan, 1926
Year defined1926
RegionSpokane, Washington
CountryUnited States
Paleobotanist Frank Hall Knowlton

The Latah Formation is a series of late Miocene lacustrine sedimentary deposits which outcrop in eastern Washington and northwestern Idaho. The lake beds are interbedded with igneous rock of the Columbia River Basalt Group. The formation was originally detailed from a site in Spokane, Washington by Dr. Kirk Bryan in a 1923 talk, and then formally described in a 1926 journal article by Joseph Pardee and Bryan.[1] When first described the formation was thought to have predated the deposition of the Columbia River Basalts, however further investigation showed them to be interbedded, being laid down in successive events.[1][2] Potassium-argon dating of the formation returned an age range of 21.3 to 12.1 million years old, indicating an Early to Middle Miocene age range.[3] Numerous fossil plants and insects have been recovered from the formation and described.[1] The Latah Formation includes the Clarkia fossil beds in Idaho.[4]

References

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  1. ^ a b c Kirkham, V.; Melville, M. (1929). "The Latah Formation". The Journal of Geology. 37 (5): 483–504. Bibcode:1929JG.....37..483K. doi:10.1086/623639. S2CID 128833093.
  2. ^ Lewis, S. (1969). "Fossil insects of the Latah Formation (Miocene) of Eastern Washington and Northern Idaho". Northwest Science. 43 (3): 99–115.
  3. ^ Gray, J.; Kittleman, L. R. (1967). "Geochronology of the Columbia River Basalt and associated floras of eastern Washington and western Idaho". American Journal of Science. 265 (4): 257–291. Bibcode:1967AmJS..265..257G. doi:10.2475/ajs.265.4.257.
  4. ^ Calede, J.; Orcutt, J.; Kehl, W.; Richards, B. (2018). "The first tetrapod from the mid-Miocene Clarkia lagerstätte (Idaho, USA)". PeerJ. 6 (e4880): e4880. doi:10.7717/peerj.4880. PMC 5995101. PMID 29900070.