Stable isotope (ẟ13C, ẟ18O) paleoecology of the late Early Miocene mammalian fauna from Buluk, Kenya

Abstract

Early Miocene deposits at Buluk in northern Kenya have produced an abundant and diverse community of mammalian fossils, including catarrhine primates, and the site is an important resource for characterizing habitat heterogeneity across East Africa during the early-middle Miocene transition. Here we present the results of stable carbon and oxygen isotope analyses of fossil tooth enamel from Buluk's ruminant artiodactyls, suoids, anthracotheres, rhinocerotids, proboscideans, and hyraxes, to address the nature of the C 3 vegetation (i.e., open-canopy versus closed-canopy and/or degree of water stress) and to determine whether C 4 plants were a dietary component of Buluk herbivores. δ 13 C enamel and δ 18 O enamel values indicate that most Buluk herbivores foraged in a C 3 -dominated mosaic of open canopy woodland habitats with no evidence of closed-canopy habitats, consistent with soil and biomarker analyses. Despite paleosol evidence for the presence of C 4 vegetation at Buluk, δ 13 C enamel results show no evidence for the consumption of C 4 biomass. This discrepancy may be caused by the presence of C 4 vegetation on the landscape that was not consumed by local herbivores in quantities that can be captured by bulk δ 13 C enamel , lack of sampling of taxa that did consume C 4 vegetation, or it may reflect differences in scale between these two data sources. Overall, the range of δ 13 C enamel values from Buluk are like the early Miocene site of Moroto and are significantly more enriched than the middle Miocene localities Maboko Island and Fort Ternan, suggesting more water-stressed environments predominated at these earlier Miocene sites in East Africa.