Sediments exposed in the Tugen Hills in the Central Rift of Kenya include an important hominin-bearing succession of volcaniclastic and fluvio-lacustrine deposits. The Hominin Sites and Paleolakes Drilling Project (HSPDP) retrieved a ~230 m core through a portion of the Chemeron Formation, containing a highly resolved succession of strata spanning events leading to the Plio-Pleistocene boundary (3.4-2.6 Ma). Trends in the character and abundance of zeolites indicate changes in paleoenvironmental conditions with varying stability identified through distinct facies assemblages. These seem to reflect high amplitude changes accompanying peak earth-orbital eccentricity at ~2.7 Ma, and relative stability at low eccentricity at ~2.9-2.7 Ma. This study suggests a decrease in K/Ca and an increase in Na/Ca with major fluctuations. Zeolites act as terrestrial climate proxies in the absence of biogenic material, aside from intervals of diatom-rich strata, and are suggesting episodes of strongest environmental fluctuations ~2.7-2.6 Ma and environmental stability ~2.9-2.7 Ma.