The Konso Formation (Fm) is exposed in the southernmost part of the Main Ethiopian Rift,>400 km SSE of Addis Ababa, approximately 160–240 km northeast of the fossiliferous exposures of the northern Turkana Basin (Figure 22.1). It occurs at the southwestern part of the Ganjuli graben, ~25–40 km south of Lake Chamo, at an altitude mostly between 1150 and 1400 m. To the north, the Konso Fm basin is separated from the lower (in altitude) Lake Chamo by a ~1200–1300 m drainage divide. Currently, the Konso Fm basin drains southeast into the Segen River that then courses due west to the northern end of the Chew Bahir rift. The Konso area is separated from the southern lowlands (Weyto/Chew Bahir basin) by a mountainous terrain of 1700–2000 m. Some degree of geographic discontinuity and altitudinal difference between the Konso and the Turkana basins probably existed in the Early Pleistocene as well, judging from the differences observed in the mammalian fauna (Suwa et al., 2003). Tentatively, we interpret the Early Pleistocene Konso Fm to represent a rift-induced small depositional basin that was distinct from the Lake Chamo depression (Nagaoka et al., 2005; Katoh et al., 2014). Most likely, the Konso basin had subsided before rifting had advanced in the Lake Chamo area to recent downthrown levels. The occurrence of the high-altitude ranging rodent Tachyoryctes at the ~1.4 Ma levels of localities KGA7 and KGA12 (currently 1400 and 1340 m altitude, respectively) suggests that Early Pleistocene deposition may have occurred at a similarly high altitude. Maximum lake expansion in the Early Pleistocene Konso Fm basin is estimated to be ~8 km (NE–SW) at <1.3–1.4 Ma (Suwa et al., 2003; Nagaoka et al., 2005).