New Discovery of Oligocene Strata in the Topernawi Formation, Turkana County, Kenya

New field observations and Ar-40/Ar-39 geochronology reveal that the Topernawi Formation of the Ekitale Basin, northern Turkana Depression, Turkana County, Kenya was deposited entirely during the Oligocene between 29.7 +/- 0.5 Ma and 29.24 +/- 0.08 Ma. These bracketing ages are determined via new Ar-40/Ar-39 geochronology on a basaltic lava flow at the base of the section and a felsic ignimbrite near the top. A newly discovered basal unit and interbedded lava flow result in a new total sedimentary thickness of 92 m. The Topernawi Formation is the oldest dated syn-rift sedimentary section in the northern Turkana Depression.