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

New sedimentary evidence reveals a unique history of C4 biomass in continental East Asia since the early Miocene

Pyrogenic carbon (PyC) and n-alkane data from sediments in the northern South China Sea reveal variations in material from C₄ plants in East Asia over the last ~19 Ma. These data indicate the likely presence of C₄ taxa during the earliest part of the record analysed, with C₄ species also prominent during the mid and late Miocene and especially the mid Quaternary. Notably the two records diverge after the mid Quaternary, when PyC data indicate a reduced contribution of C₄ taxa to biomass burning, whereas plant-derived n-alkanes indicate a greater abundance of C₄ plants. This divergence likely reflects differences in the predominant source areas of organic materials accumulating at the coring site, with PyC representing a larger source area that includes material transported in the atmosphere from more temperate (relatively cooler and drier) parts of East Asia. Variations in the relative abundances of C₃ and C₄ taxa appear to be linked to a combination of environmental factors that have varied temporally and geographically and that are unique to East Asia. A major expansion of C₄ biomass in warmer subtropical parts of eastern Asia from ~1 Ma and particularly from ~0.4 Ma is later than other parts of the world.