PALEOENVIRONMENTAL RECONSTRUCTION OF EARLY MIOCENE CATARRHINE LOCALITIES USING FOSSIL FOREST PALEOSOLS FROM RUSINGA ISLAND, LAKE VICTORIA, KENYA

Early Miocene deposits on Rusinga and Mfangano Islands, Kenya have produced more than 100 species of fossil vertebrates, including five species of primates that are critical for understanding the origin of the ape-human clade. Despite this wealth of data, there is ongoing debate over the paleoenviroment in which these primates lived. Recently, evidence for preservation of an in situ fossil forest was discovered within a 0.5 – 1.4m thick paleosol from the Kibanga Member (Hiwegi Formation) at Rusinga's R3 locality. Importantly, new fossil primates were found in direct association with this forest. Moreover, the iconic Dendropithecus primates discovered at R3a can also be shown to correspond to the same paleosol. The paleosol is clay silt to silty sand, and contains many coarse sandstone-filled stump casts up to 1.6 m in diameter with extensive, well-preserved root systems that extend horizontally up to distances of 4 m away from stump casts. Root casts up to 50 cm in diameter were excavated extensively to verify size, direction of branching and connection to stump casts. Paleosols found at the fossil locality are weakly developed Entisols formed from two discrete ash layers, with colors varying from red-brown to grayish-brown to pinkish gray, suggesting well- drained conditions, but short-lived landscape stability. Tree stump casts occur as a mappable and continuous layer, except where truncated by coarse stream bedload sandstones and conglomerates, suggesting a forested ecosystem proximal to a fluvial environment. Large fossil tree leaves collected from the base of a coarse-grained sandstone that truncates the top of the paleosol, as well as several vertebrate taxa from the R3 locality including squirrels (Vulcanisciurus), chevrotains (Dorcatherium), and snakes (Pythonidae) are consistent with this interpretation. This study demonstrates the utility of paleopedology to examining paleoanthroplogical problems.