Journal ArticleNew Discovery of Oligocene Strata in the Topernawi Formation, Turkana County, KenyaSousa, Francis J.; Cox, Stephen E.; Hemming, Sidney R.; Rasbury, E. Troy; Steponaitis, Elena; Hatton, Kevin; Saslaw, Mae; Henkes, Gregory; Princehouse, Patricia; Vitek, Natasha S.; Nengo, IsaiahNew field observations and 40 Ar/ 39 Ar 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 40 Ar/ 39 Ar 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.2022-02-0310330555Frontiers in Earth Science102296-6463https://doi.org/10.3389/feart.2022.7990972124790; 2124791; 2124792; 2021666; 2021579National Science Foundation