Terrestrial biome distribution in the Late Neogene inferred from a black carbon record in the northeastern equatorial Pacific

The appearance and expansion of C(4) plants in the Late Cenozoic was a dramatic example of terrestrial ecological change. The fire hypothesis, which suggests fire as a major cause of C(4) grassland is gaining support, yet a more detailed relationship between fire and vegetation-type change remains unresolved. We report the content and stable carbon isotope record of black carbon (BC) in a sediment core retrieved from the northeastern equatorial Pacific that covers the past 14.3 million years. The content record of BC suggests the development process of a flammable ecosystem. The stable carbon isotope record of BC reveals the existence of the Late Miocene C(4) expansion, the ‘C(4) maximum period of burned biomass’ during the Pliocene to Early Pleistocene, and the collapse of the C(4) in the Late Pleistocene. Records showing the initial expansion of C(4) plants after large fire support the role of fire as a destructive agent of C(3)-dominated forest, yet the weak relationships between fire and vegetation after initial expansion suggest that environmental advantages for C(4) plants were necessary to maintain the development of C(4) plants during the late Neogene. Among the various environmental factors, aridity is likely most influential in C(4) expansion.